深入Java核心

àì夳堔傛蜴生んèń 2022-06-12 02:14 130阅读 0赞

## 类加载 ##

> 类加载负责加载编译后的class文件（字节码文件）到JVM当中。

*  在JRE中，类加载器主要分为以下几种：
    
     *  `引导类加载器（Bootstrap）`
        
         *  它本身使用C/C++语言实现的，负责加载Java的核心类库，在jre\\lib目录中，当中包括如rt.jar，这些都是Java自带的核心类库，必须由它来完成加载。
     *  `拓展/扩展类加载器（Extension）`
        
         *  这个加载器就是由Java语言实现，负责加载jre\\lib\\ext目录下的类库，这个目录下的类库都是一些扩展类。
     *  `应用程序/系统类加载器（Application）`
        
         *  这个类加载器同样使用Java语言实现，它主要负责加载classpath下面的所有类库，通常我们编写的Java类都是由这个类加载器完成加载。
 *  三个类加载器的初始化过程：当程序运行时，首先会初始化引导类加载器，它就负责创建和初始化扩展类加载器，当扩展类加载器完成初始化之后，又负责创建和初始化系统类加载器。
 *  这些类加载器协同起来完成整个类加载的过程，因此这些类加载器的加载模式是基于“双亲委托模型”。
 *  [![双亲委托模型][E5_8F_8C_E4_BA_B2_E5_A7_94_E6_89_98_E6_9C_BA_E5_88_B6.png]][E5_8F_8C_E4_BA_B2_E5_A7_94_E6_89_98_E6_9C_BA_E5_88_B6.png]

### 举例说明 ###

*  当我们编写一个Java类时，首先负责加载这个类的加载器是系统类加载器，但是它不会立马就去执行加载，而是先把这个任务交给父加载器（扩展类加载器），而扩展类加载器同样也会将这个任务交给父加载器（引导类加载器），最终当引导类加载器不能去加载这个类的时候（也就是在自己加载职责范围找不到的时候），又会将这个任务交回给子加载器。以此类推，最终我们编写的类都会配置在classpath环境中，所以，这个类的加载任务还是回到系统类加载器来完成。
    
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         </div></pre> </td> 
       <td style="margin:0px; padding:0px; border:none; outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> <pre style="margin-top:0px; margin-bottom:0px; padding:0px; border:none; outline:0px; font-weight:inherit; font-style:inherit; font-family:Menlo,Consolas,&quot;Source Code Pro&quot;,Inconsolata,Monaco,monospace,&quot;Microsoft YaHei&quot;,&quot;PingFang SC&quot;,&quot;Hiragino Sans GB&quot;,&quot;WenQuanYi Micro Hei&quot;; font-size:1em; vertical-align:baseline; background:0px 0px; overflow:auto; color:rgb(77,77,76); line-height:1.3rem">
            
             
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          <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; color:rgb(137,89,168)">public</span> 
             
              
          <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; color:rgb(113,140,0)"><span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; color:rgb(137,89,168)">class</span> <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; color:rgb(142,144,140)">Test</span> </span>{
            
             
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             	String name;
            
             
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         <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; line-height:1.3rem">	
             
              
          <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; color:rgb(66,113,174)"><span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; color:rgb(137,89,168)">public</span> <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; color:rgb(137,89,168)">void</span> <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; color:rgb(142,144,140)">say</span><span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; color:rgb(245,135,31)">()</span></span>{
            
             
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             		System.out.println(
             
              
          <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; color:rgb(113,140,0)">"Hello Word"</span>);
            
             
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             	}
            
             
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         <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; line-height:1.3rem">	
            
             
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         <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; line-height:1.3rem">	
             
              
          <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; color:rgb(142,144,140)">// 程序的入口的方法，和具体类无关</span>
            
             
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         <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; line-height:1.3rem">	
             
              
          <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; color:rgb(66,113,174)"><span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; color:rgb(137,89,168)">public</span> <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; color:rgb(137,89,168)">static</span> <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; color:rgb(137,89,168)">void</span> <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; color:rgb(142,144,140)">main</span><span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; color:rgb(245,135,31)">(String[] args)</span> </span>{
            
             
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             		Test t = 
             
              
          <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; color:rgb(137,89,168)">new</span> Test();	
            
             
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             		t.say();
            
             
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         <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; line-height:1.3rem"></div>
            
             
         <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; line-height:1.3rem">		
             
              
          <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; color:rgb(142,144,140)">// 得到当前的类加载器ApplicationClassLoader</span>
            
             
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             		ClassLoader cl = Test.class.getClassLoader();
            
             
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             		System.out.println(cl);
            
             
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         <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; line-height:1.3rem"></div>
            
             
         <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; line-height:1.3rem">		
             
              
          <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; color:rgb(142,144,140)">// 得到ApplicationClassLoader的父类加载器ExtensionClassLoader</span>
            
             
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             		ClassLoader extCl = cl.getParent();
            
             
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         <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; line-height:1.3rem">
          
              
             		System.out.println(extCl);
            
             
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         <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; line-height:1.3rem"></div>
            
             
         <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; line-height:1.3rem">		
             
              
          <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; color:rgb(142,144,140)">// 得到ExtensionClassLoader的父类加载器BootstrapClassLoader</span>
            
             
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         <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; line-height:1.3rem">		
             
              
          <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; color:rgb(142,144,140)">// 由于BootstrapClassLoader是用C/C++语言编写的，在java中无法直接使用</span>
            
             
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          <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; color:rgb(142,144,140)">// 所以才会返回一个null</span>
            
             
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             		ClassLoader bootCl = extCl.getParent();
            
             
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             		System.out.println(bootCl);
            
             
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             	}
            
             
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             }
            
             
         </div></pre> </td> 
      </tr> 
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 *  当一个class文件最终加载到jvm之后，就表示类加载这个阶段已经全部完成。接下来就是对整个class文件的内容进行解析和做内存的分配。

## 内存分配 ##

> 当JVM运行起来的时候就会给内存划分空间，那么这块空间称之为运行时数据区。  
> (`备注：`当一个Java源程序编译成class字节码文件之后，字节码文件里存放的都是二进制的汇编命令，当程序运行的时候，JVM会将这个二进制的命令逐行解释，交给CPU去执行)

*  运行时数据区将划分为以下几块内容：
    
     *  `栈`
        
         *  每一个线程运行起来的时候就会对应一个栈（线程栈），栈当中存放的数据是被当前线程所独有的。而栈当中存放的是栈帧，当线程调用一个方法的时候，就会形成一个栈帧，并将这个栈帧进行压栈操作，当方法执行完之后就会将这个栈帧进行出栈操作。这个栈帧里面包括（局部变量、操作数栈、指向当前方法对应类的常量池引用、方法的返回地址等信息）。  
            (`备注：`由于局部变量都是存放在栈中，而每一个线程都对应自己的线程栈，因此局部变量是线程安全的，不会才产生资源共享的情况。)
         *  [![递归栈][E9_80_92_E5_BD_92_E6_A0_88.png]][E9_80_92_E5_BD_92_E6_A0_88.png]
     *  `本地方法栈`
        
         *  本地方法栈的机制和栈的机制类似，区别在于，栈是运行Java所实现的方法，而本地方法栈是运行的本地方法(Native Method)。所谓的本地方法指的是在本地jvm中需要调用非Java语言所实现的方法，例如c语言。在JVM的规范中，其实没有强制性要求实现方一定要划分出本地方法栈的和具体的实现，这一部分可以根据实现方具体要求来实现。因此在HotSport虚拟机的实现中就将方法栈和本地方法栈二合为一。
         *  [![本地方法栈][E6_9C_AC_E5_9C_B0_E6_96_B9_E6_B3_95_E6_A0_881.png]][E6_9C_AC_E5_9C_B0_E6_96_B9_E6_B3_95_E6_A0_881.png]
     *  `程序计数器`
        
         *  程序计数器也可以称之为PC寄存器。它主要用于存放当前程序下一条将要执行的指令地址。CPU会根据这个地址找到对应的指令来执行。通俗的讲就是指令缓存。这个寄存器是有JVM内部实现的，并不是物理概念上的寄存器，但是JVM在实现功能的逻辑上是相同的。
     *  `堆`
        
         *  堆内存中主要存放创建的对象以及数组。 堆内存是可以被多个线程所共享的一块区域,因此多个线程栈都可以去访问同一块堆的内存区域。堆里面的每一对象都存放了该实例的实例变量。
         *  当在方法中定义了一个局部变量，如果这个变量是基本数据类型，那么这个变量的值就直接存放在栈中，如果这个变量是引用数据类型，那么这个对象变量就存放在堆内存中，而栈中存放的是一个指向堆内存中这个对象的首地址。  
            (`备注：`Java中除了8个基本数据类型以外的所有类型都是引用数据类型)
         *  引用
         *  [![引用][E5_A0_86_EF_BC_9A_E5_BC_95_E7_94_A8.png]][E5_A0_86_EF_BC_9A_E5_BC_95_E7_94_A8.png]
         *  更改
         *  [![更改][E5_A0_86_EF_BC_9A_E5_AF_B9_E8_B1_A1_E6_9B_B4_E6_94_B9.png]][E5_A0_86_EF_BC_9A_E5_AF_B9_E8_B1_A1_E6_9B_B4_E6_94_B9.png]
         *  数组
         *  [![数组][E5_A0_86_EF_BC_9A_E6_95_B0_E7_BB_84.png]][E5_A0_86_EF_BC_9A_E6_95_B0_E7_BB_84.png]
         *  循环
         *  [![循环][E5_A0_86_EF_BC_9A_E5_BE_AA_E7_8E_AF.png]][E5_A0_86_EF_BC_9A_E5_BE_AA_E7_8E_AF.png]
         *  实例变量和静态变量的区别：
            
             *  `实例变量：`实例变量是随着对象的创建而创建，而实例是存放在堆中，所以实例变量自然也就跟实例一并保存在堆内存。只要创建多少个实例，就会有多少份实例变量。当实例被回收的时候，实例变量也随之而销毁。
             *  `静态变量：`静态变量也叫类变量，它是在类加载的时候就已经初始化好，并存放在方法区，并且只有一份，所以它是被多个实例所共享的一个变量。
     *  `方法区`
        
         *  方法区在JVM中也是一个非常重要的一块内存区域，它和堆一样，是可以被多个线程所共享的一块区域。这个区域中主要存放了每一个加载的class文件信息。  
            在一个class文件中主要包含`魔数`(代码中出现但没有解释的数字常量或字符串)（用来确定是否是一个class文件）、常量池（常量池在下面会有完整说明）、访问标志（当前的class是类还是接口，是否是抽象类，  
            是否是public修饰，是否使用了`final`修饰等描述信息…）、字段表集合信息（使用什么访问修饰符、是实例变量还是静态变量，是否用`final`修饰等描述信息…）、  
            方法表集合信息（访问修饰符，是否静态方法，是否用final修饰，是否用了`synchronized`修饰，是否是`native`方法…）等内容。当一个类加载器加载一个class文件的时候，  
            会根据这个class文件的内容创建一个Class对象，而这个Class对象就包括了上述的这些内容。后续要创建这个类的所有实例，都是通过这个Class对象创建出来的。
         *  [![方法区][E6_96_B9_E6_B3_95_E5_8C_BA.png]][E6_96_B9_E6_B3_95_E5_8C_BA.png]
     *  `常量池`
        
         *  常量池也是方法区中的一部分，它存放的内容是class文件中最重要的资源，JVM为每一个class对象都维护一个常量池。它主要存储两种类型的常量。
            
            1.  字面常量
                
                 *  字面常量通常就是在Java中定义的字面量值，如：int i =1,这个1就是字面量；String s = (“abc”)，这个abc就是字面量。或者使用final修饰的常量值等等。
            2.  符号引用
                
                 *  符号引用主要包括类和接口的完整类名、属性字段的名称和描述符、方法名称和描述符等信息
         *  [![常量池][E5_B8_B8_E9_87_8F_E6_B1_A0.jpg]][E5_B8_B8_E9_87_8F_E6_B1_A0.jpg]
 *  在Java当中，8个基本数据类型都有对应的包装类型，而大部分包装类型都实现了常量池的技术，除了`Double`和`Float`类。  
    (`备注说明：`在JDK8之后，方法区已经取消，方法区被一个叫MetaSpace，它和堆合并到一起管理)
 *  内存运行时数据区
 *  [![内存运行时数据区][E5_86_85_E5_AD_98_E8_BF_90_E8_A1_8C_E6_97_B6_E6_95_B0_E6_8D_AE_E5_8C_BA.png]][E5_86_85_E5_AD_98_E8_BF_90_E8_A1_8C_E6_97_B6_E6_95_B0_E6_8D_AE_E5_8C_BA.png]
 *  `扯了好多Java虚拟机的内容，也没讲多深，因为这里主要的目的是为了大家方便理解Java反射机制，下面正式进入正题`

## Class对象 ##

> 当ClassLoader加载一个class文件到JVM的时候，会自动创建一个该类的Class对象，并且这个对象是唯一的，后续要创建这个类的任何实例，都会根据这个Class对象来创建。因此每当加载一个class文件的时候，都会创建一个与之对应的Class对象。

*  解析一个类的各个部分，形成一个对象。
 *  [![String类加载示意图][String]][String]
 *  外存中的类，加载到内存中，会形成该对象的Class类，例如：String类，加载到内存中，就是StringClass对象。  
    也就是说类是java.lang.Class类的实例对象，而Class是所有类的类  
    对于普通的对象，一般都的创建方式：
    
    <table style="margin:0px; padding:0px; border:none; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; border-collapse:collapse; border-spacing:0px; width:auto; max-width:65em; empty-cells:show"> 
     <tbody style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline"> 
      <tr style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; height:35px"> 
       <td style="margin:0px; padding:0px; border:none; outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px; white-space:nowrap"> <pre style="margin-top:0px; margin-bottom:0px; padding:0px 1em 0px 0px; border:none; outline:0px; font-weight:inherit; font-style:inherit; font-family:Menlo,Consolas,&quot;Source Code Pro&quot;,Inconsolata,Monaco,monospace,&quot;Microsoft YaHei&quot;,&quot;PingFang SC&quot;,&quot;Hiragino Sans GB&quot;,&quot;WenQuanYi Micro Hei&quot;; font-size:0.85rem; vertical-align:baseline; background:0px 0px; overflow:auto; color:rgb(211,211,211); line-height:1.3rem; text-align:right">
            
             
         <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; font-size:13.6px; vertical-align:baseline; line-height:1.3rem">
          
              
             1
            
             
         </div></pre> </td> 
       <td style="margin:0px; padding:0px; border:none; outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> <pre style="margin-top:0px; margin-bottom:0px; padding:0px; border:none; outline:0px; font-weight:inherit; font-style:inherit; font-family:Menlo,Consolas,&quot;Source Code Pro&quot;,Inconsolata,Monaco,monospace,&quot;Microsoft YaHei&quot;,&quot;PingFang SC&quot;,&quot;Hiragino Sans GB&quot;,&quot;WenQuanYi Micro Hei&quot;; font-size:1em; vertical-align:baseline; background:0px 0px; overflow:auto; color:rgb(77,77,76); line-height:1.3rem">
            
             
         <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; line-height:1.3rem">
          
              
             String s = 
             
              
          <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; color:rgb(137,89,168)">new</span> String();
            
             
         </div></pre> </td> 
      </tr> 
     </tbody> 
    </table>
 *  既然类都是Class的对象，那么能否像普通对象一样创建呢，当看源码时，是这样写的 ：
    
    <table style="margin:0px; padding:0px; border:none; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; border-collapse:collapse; border-spacing:0px; width:auto; max-width:65em; empty-cells:show"> 
     <tbody style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline"> 
      <tr style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; height:35px"> 
       <td style="margin:0px; padding:0px; border:none; outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px; white-space:nowrap"> <pre style="margin-top:0px; margin-bottom:0px; padding:0px 1em 0px 0px; border:none; outline:0px; font-weight:inherit; font-style:inherit; font-family:Menlo,Consolas,&quot;Source Code Pro&quot;,Inconsolata,Monaco,monospace,&quot;Microsoft YaHei&quot;,&quot;PingFang SC&quot;,&quot;Hiragino Sans GB&quot;,&quot;WenQuanYi Micro Hei&quot;; font-size:0.85rem; vertical-align:baseline; background:0px 0px; overflow:auto; color:rgb(211,211,211); line-height:1.3rem; text-align:right">
            
             
         <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; font-size:13.6px; vertical-align:baseline; line-height:1.3rem">
          
              
             1
            
             
         </div>
            
             
         <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; font-size:13.6px; vertical-align:baseline; line-height:1.3rem">
          
              
             2
            
             
         </div>
            
             
         <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; font-size:13.6px; vertical-align:baseline; line-height:1.3rem">
          
              
             3
            
             
         </div></pre> </td> 
       <td style="margin:0px; padding:0px; border:none; outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> <pre style="margin-top:0px; margin-bottom:0px; padding:0px; border:none; outline:0px; font-weight:inherit; font-style:inherit; font-family:Menlo,Consolas,&quot;Source Code Pro&quot;,Inconsolata,Monaco,monospace,&quot;Microsoft YaHei&quot;,&quot;PingFang SC&quot;,&quot;Hiragino Sans GB&quot;,&quot;WenQuanYi Micro Hei&quot;; font-size:1em; vertical-align:baseline; background:0px 0px; overflow:auto; color:rgb(77,77,76); line-height:1.3rem">
            
             
         <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; line-height:1.3rem">
             
              
          <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; color:rgb(66,113,174)"><span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; color:rgb(137,89,168)">private</span> <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; color:rgb(142,144,140)">Class</span><span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; color:rgb(245,135,31)">(ClassLoader loader)</span> </span>{
            
             
         </div>
            
             
         <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; line-height:1.3rem">
          
              
                 classLoader = loader;
            
             
         </div>
            
             
         <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; line-height:1.3rem">
          
              
             }
            
             
         </div></pre> </td> 
      </tr> 
     </tbody> 
    </table>
 *  源码里构造器是私有的，只有JVM可以创建Class的对象，虽然我们不能new一个Class对象，但是可以从已有的类得到一个Class对象，共有三种方式，如下：
    
    <table style="margin:0px; padding:0px; border:none; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; border-collapse:collapse; border-spacing:0px; width:auto; max-width:65em; empty-cells:show"> 
     <tbody style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline"> 
      <tr style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; height:35px"> 
       <td style="margin:0px; padding:0px; border:none; outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px; white-space:nowrap"> <pre style="margin-top:0px; margin-bottom:0px; padding:0px 1em 0px 0px; border:none; outline:0px; font-weight:inherit; font-style:inherit; font-family:Menlo,Consolas,&quot;Source Code Pro&quot;,Inconsolata,Monaco,monospace,&quot;Microsoft YaHei&quot;,&quot;PingFang SC&quot;,&quot;Hiragino Sans GB&quot;,&quot;WenQuanYi Micro Hei&quot;; font-size:0.85rem; vertical-align:baseline; background:0px 0px; overflow:auto; color:rgb(211,211,211); line-height:1.3rem; text-align:right">
            
             
         <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; font-size:13.6px; vertical-align:baseline; line-height:1.3rem">
          
              
             1
            
             
         </div>
            
             
         <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; font-size:13.6px; vertical-align:baseline; line-height:1.3rem">
          
              
             2
            
             
         </div>
            
             
         <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; font-size:13.6px; vertical-align:baseline; line-height:1.3rem">
          
              
             3
            
             
         </div>
            
             
         <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; font-size:13.6px; vertical-align:baseline; line-height:1.3rem">
          
              
             4
            
             
         </div>
            
             
         <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; font-size:13.6px; vertical-align:baseline; line-height:1.3rem">
          
              
             5
            
             
         </div>
            
             
         <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; font-size:13.6px; vertical-align:baseline; line-height:1.3rem">
          
              
             6
            
             
         </div></pre> </td> 
       <td style="margin:0px; padding:0px; border:none; outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> <pre style="margin-top:0px; margin-bottom:0px; padding:0px; border:none; outline:0px; font-weight:inherit; font-style:inherit; font-family:Menlo,Consolas,&quot;Source Code Pro&quot;,Inconsolata,Monaco,monospace,&quot;Microsoft YaHei&quot;,&quot;PingFang SC&quot;,&quot;Hiragino Sans GB&quot;,&quot;WenQuanYi Micro Hei&quot;; font-size:1em; vertical-align:baseline; background:0px 0px; overflow:auto; color:rgb(77,77,76); line-height:1.3rem">
            
             
         <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; line-height:1.3rem">
             
              
          <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; color:rgb(142,144,140)">// 类名.class 通过获取类的静态成员变量class得到(任何类都有一个隐含的静态成员变量class)</span>
            
             
         </div>
            
             
         <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; line-height:1.3rem">
          
              
             Class&lt;?&gt; clazz = String.class;
            
             
         </div>
            
             
         <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; line-height:1.3rem">
             
              
          <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; color:rgb(142,144,140)">// 对象.getClass</span>
            
             
         </div>
            
             
         <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; line-height:1.3rem">
          
              
             Class&lt;?&gt; clazz2 = 
             
              
          <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; color:rgb(137,89,168)">new</span> String().getClass();
            
             
         </div>
            
             
         <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; line-height:1.3rem">
             
              
          <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; color:rgb(142,144,140)">// Class.forName("全量限定名")</span>
            
             
         </div>
            
             
         <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; line-height:1.3rem">
          
              
             Class&lt;?&gt; clazz3 = Class.forName(
             
              
          <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; color:rgb(113,140,0)">"java.lang.String"</span>);
            
             
         </div></pre> </td> 
      </tr> 
     </tbody> 
    </table>
 *  (`注意：`这三种方式都是利用反射获取的都是同一个Class对象，这也叫做String的类类型，也就是描述何为类，一个类都有哪些东西，所以可以通过类类型知道一个类的属性和方法，并可以调用一个类的属性和方法，这就是反射的基础。)

## 反射 ##

> 反射是指`在程序的运行期间动态的去操作某个Class对象里面的成员`（包括类信息、属性信息、方法信息等元素）。它可以让Java这种静态语言具备一定的动态性。目前大部分的开源框架实现都是基于反射的机制实现。  
> JVM → 类加载 → class文件 → 创建 → Class对象 → 构建类的实例 → instance(实例)；  
> 重点在运行时动态的操作Class对象。

### 反射机制的利与弊 ###

为何要用反射机制？直接new对象不ok了吗，这就涉及到了动态与静态的概念

*  静态编译：在编译时确定类型，绑定对象,即通过。
 *  动态编译：运行时确定类型，绑定对象。动态编译最大限度发挥了java的灵活性，体现了多态的应用，有利于降低类之间的藕合。
 *  优点:
    
     *  可以实现动态创建对象和编译。比如，一个软件，不可能第一个版本就把它设计的很完美，当这个程序编译成功，发布后，当发现某些功能需要更新时，我们不可能要用户把旧版的卸载，再重新安装新的版本。采用静态的话，需要把整个程序重新编译一次才可以实现功能的更新，而采用反射机制的话，它就可以不用卸载，只需要在运行时才动态的创建和编译，就可以实现该功能。  
        一句话总结：`运行期类型的判断，动态类加载，动态代理就使用了反射`
 *  缺点:  
    1.对性能有影响。反射相当于一系列解释操作，通知JVM要做的事情。性能比直接的java代码执行相同的操作要慢很多。  
    2.由于反射允许代码执行一些在正常情况下不被允许的操作（比如访问私有的属性和方法），所以使用反射可能会导致意料之外的副作用，反射代码破坏了抽象性，因此当平台发生改变的时候，代码的行为就有可能也随着变化。

### 反射机制的相关操作 ###

#### 创建实例 ####

#### 动态操作属性 ####

*  通过Class对象可以动态的获取和操作类中的属性，属性在JDK中有一个类来进行封装，就是Field,Field提供了一些常用的API方法让我们去访问和操作类中的属性
    
    `getField()` // 获取所有公开的属性字段（包括继承父类的公有属性）  
    `getDeclaredField()` // 获取本类所有（包括公有和私有，但是不包括父类的）的属性字段（注意：如果要访问和操作私有属性，必须调用setAccessible方法，打开访问开关）  
    `getFields()` // 获取所有公有的属性（包括继承自父类的公有属性）  
    `getDeclaredFields()` // 获取本类所有的属性（包括共有和私有的，但是不包括父类的）  
    `set()` // 给属性赋值，需要传入两个参数，第一个参数是当前类的一个实例，第二个参数是具体要赋予的值  
    `get()` // 获取属性的值，需要传入一个当前类的实例作为参数  
    `getName()` // 获取属性的名称  
    `getType()` // 获取属性的类型  
    `isAnnotationPresent()` // 判断该属性上是否定义了指定的注解，需要传入一个注解的Class对象作为参数  
    `getAnnotation()` // 获取当前属性上的注解对象，需要传入一个注解的Class对象作为参数
    
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         </div></pre> </td> 
       <td style="margin:0px; padding:0px; border:none; outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> <pre style="margin-top:0px; margin-bottom:0px; padding:0px; border:none; outline:0px; font-weight:inherit; font-style:inherit; font-family:Menlo,Consolas,&quot;Source Code Pro&quot;,Inconsolata,Monaco,monospace,&quot;Microsoft YaHei&quot;,&quot;PingFang SC&quot;,&quot;Hiragino Sans GB&quot;,&quot;WenQuanYi Micro Hei&quot;; font-size:1em; vertical-align:baseline; background:0px 0px; overflow:auto; color:rgb(77,77,76); line-height:1.3rem">
            
             
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          <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; color:rgb(66,113,174)"><span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; color:rgb(137,89,168)">public</span> <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; color:rgb(137,89,168)">static</span> <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; color:rgb(137,89,168)">void</span> <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; color:rgb(142,144,140)">main</span><span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; color:rgb(245,135,31)">(String[] args)</span> <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; color:rgb(137,89,168)">throws</span> Exception </span>{
            
             
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          <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; color:rgb(142,144,140)">// 在反射操作之前的第一步，就是要先获取Class对象</span>
            
             
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                 Class&lt;?&gt; clazz = Class.forName(
             
              
          <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; color:rgb(113,140,0)">"org.demo.reflect.bean.People"</span>);
            
             
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          <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; color:rgb(142,144,140)">// 根据Class对象创建一个实例</span>
            
             
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                 Object instance = clazz.newInstance();
            
             
         </div>
            
             
         <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; line-height:1.3rem">    
             
              
          <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; color:rgb(142,144,140)">// 获取指定的属性</span>
            
             
         </div>
            
             
         <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; line-height:1.3rem">
          
              
                 Field f1 = clazz.getField(
             
              
          <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; color:rgb(113,140,0)">"userName"</span>);
            
             
         </div>
            
             
         <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; line-height:1.3rem">    
             
              
          <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; color:rgb(142,144,140)">// 获取属性的值,get方法需要传入一个当前类的实例</span>
            
             
         </div>
            
             
         <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; line-height:1.3rem">
          
              
                 Object value = f1.get(instance);
            
             
         </div>
            
             
         <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; line-height:1.3rem">
          
              
                 System.out.println(value);
            
             
         </div>
            
             
         <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; line-height:1.3rem"></div>
            
             
         <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; line-height:1.3rem">    
             
              
          <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; color:rgb(142,144,140)">// 通过反射给属性赋值</span>
            
             
         </div>
            
             
         <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; line-height:1.3rem">    
             
              
          <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; color:rgb(142,144,140)">// 第一个参数是当前类的实例，第二个参数是要赋予的值</span>
            
             
         </div>
            
             
         <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; line-height:1.3rem">
          
              
                 f1.set(instance, 
             
              
          <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; color:rgb(113,140,0)">"godql"</span>);
            
             
         </div>
            
             
         <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; line-height:1.3rem">
          
              
                 value = f1.get(instance);
            
             
         </div>
            
             
         <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; line-height:1.3rem">
          
              
                 System.out.println(value);
            
             
         </div>
            
             
         <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; line-height:1.3rem"></div>
            
             
         <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; line-height:1.3rem">    
             
              
          <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; color:rgb(142,144,140)">// 获取一个私有的属性</span>
            
             
         </div>
            
             
         <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; line-height:1.3rem">    
             
              
          <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; color:rgb(142,144,140)">// 如果需要访问和操作私有的成员，必须打开访问开关</span>
            
             
         </div>
            
             
         <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; line-height:1.3rem">    
             
              
          <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; color:rgb(142,144,140)">// 打开访问开关其实就是破坏封装</span>
            
             
         </div>
            
             
         <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; line-height:1.3rem">
          
              
                 Field f2 = clazz.getDeclaredField(
             
              
          <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; color:rgb(113,140,0)">"age"</span>);
            
             
         </div>
            
             
         <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; line-height:1.3rem">    
             
              
          <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; color:rgb(142,144,140)">// 强制打开访问权限</span>
            
             
         </div>
            
             
         <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; line-height:1.3rem">
          
              
                 f2.setAccessible(
             
              
          <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; color:rgb(137,89,168)">true</span>);
            
             
         </div>
            
             
         <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; line-height:1.3rem">
          
              
                 Object value2 = f2.get(instance);
            
             
         </div>
            
             
         <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; line-height:1.3rem">
          
              
                 System.out.println(value2);
            
             
         </div>
            
             
         <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; line-height:1.3rem">
          
              
                 f2.set(instance, 
             
              
          <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; color:rgb(245,135,31)">30</span>);
            
             
         </div>
            
             
         <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; line-height:1.3rem">
          
              
                 value2 = f2.get(instance);
            
             
         </div>
            
             
         <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; line-height:1.3rem">
          
              
                 System.out.println(value2);
            
             
         </div>
            
             
         <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; line-height:1.3rem"></div>
            
             
         <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; line-height:1.3rem">    
             
              
          <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; color:rgb(142,144,140)">// 获取属性的名称</span>
            
             
         </div>
            
             
         <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; line-height:1.3rem">
          
              
                 System.out.println(f1.getName());
            
             
         </div>
            
             
         <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; line-height:1.3rem">
          
              
                 System.out.println(f2.getName());
            
             
         </div>
            
             
         <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; line-height:1.3rem"></div>
            
             
         <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; line-height:1.3rem">    
             
              
          <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; color:rgb(142,144,140)">// 获取属性的类型</span>
            
             
         </div>
            
             
         <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; line-height:1.3rem">
          
              
                 System.out.println(f1.getType());
            
             
         </div>
            
             
         <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; line-height:1.3rem">
          
              
                 System.out.println(f2.getType());
            
             
         </div>
            
             
         <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; line-height:1.3rem"></div>
            
             
         <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; line-height:1.3rem">    
             
              
          <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; color:rgb(142,144,140)">// 获取所有公有的属性(包括继承自父类的公有属性)</span>
            
             
         </div>
            
             
         <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; line-height:1.3rem">
          
              
                 Field[] fs1 = clazz.getFields();
            
             
         </div>
            
             
         <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; line-height:1.3rem">    
             
              
          <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; color:rgb(142,144,140)">// 获取本类所有的属性（包括共有和私有的，但是不包括父类的）</span>
            
             
         </div>
            
             
         <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; line-height:1.3rem">
          
              
                 Field[] fs2 = clazz.getDeclaredFields();
            
             
         </div>
            
             
         <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; line-height:1.3rem"></div>
            
             
         <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; line-height:1.3rem">    
             
              
          <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; color:rgb(142,144,140)">// 判断当前属性上是否定义了注解</span>
            
             
         </div>
            
             
         <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; line-height:1.3rem">
          
              
                 System.out.println(f1.isAnnotationPresent(MyAnno.class));
            
             
         </div>
            
             
         <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; line-height:1.3rem">
          
              
                 ystem.out.println(f2.isAnnotationPresent(MyAnno.class));
            
             
         </div>
            
             
         <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; line-height:1.3rem"></div>
            
             
         <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; line-height:1.3rem">    
             
              
          <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; color:rgb(142,144,140)">// 获取属性上定义的注解</span>
            
             
         </div>
            
             
         <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; line-height:1.3rem">
          
              
                 MyAnno anno = f1.getAnnotation(MyAnno.class);
            
             
         </div>
            
             
         <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; line-height:1.3rem">    
             
              
          <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; color:rgb(142,144,140)">// 获取注解上的属性值</span>
            
             
         </div>
            
             
         <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; line-height:1.3rem">
          
              
                 System.out.println(anno.name());
            
             
         </div>
            
             
         <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; line-height:1.3rem">
          
              
             }
            
             
         </div></pre> </td> 
      </tr> 
     </tbody> 
    </table>

#### 动态操作方法 ####

*  对于Class中的方法，API也提供了相应的类来进行封装，就是Method
    
    `getMethod()` // 获取指定的公共的方法（包括继承自父类公共的），需要传递两个参数，第一个参数是方法名称，第二个参数是一个可变参数，传递的是方法参数的类型  
    `getMethods()` // 获取所有的公共的方法（包括继承父类的公共方法）。  
    `getDeclaredMethod()` // 获取本类中指定的方法（包括私有和共有的，不包括父类的），需要传递两个参数，第一个参数是方法名称，第二个参数是一个可变参数，传递的是方法参数的类型。如果是私有方法，同样需要先打开访问开关(setAccessible(true))。  
    `getDeclaredMethods()` // 获取本地中所有的方法（包括私有和公共的，不包括父类）  
    `getName()` // 获取方法名称  
    `getReturnType()` // 获取方法的返回值类型  
    `getParameterTypes()` // 获取方法中所有的参数类型  
    `getParameterCount()`// 获取方法中参数的总个数  
    `getParameters()` // (JDK1.8新特性)获取方法中所有的参数信息，每一个参数信息都是一个Parameter类的对象。可以通过这个对象获取各个参数的类型以及名称(注意：如果要获取参数名，在编译的时候需要加上一个parameters参数，如：javac -parameters Xxx.java。或者是在开发环境中设置相应的编译选项)。  
    `invoke()` // 回调当前方法,需要传递两个参数，第一个是当前类的实例，第二个是一个可变参数，需要传入调用方法是所需的参数值。

<table style="margin:0px; padding:0px; border:none; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; border-collapse:collapse; border-spacing:0px; width:auto; max-width:65em; empty-cells:show"> 
 <tbody style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline"> 
  <tr style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; height:35px"> 
   <td style="margin:0px; padding:0px; border:none; outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px; white-space:nowrap"> <pre style="margin-top:0px; margin-bottom:0px; padding:0px 1em 0px 0px; border:none; outline:0px; font-weight:inherit; font-style:inherit; font-family:Menlo,Consolas,&quot;Source Code Pro&quot;,Inconsolata,Monaco,monospace,&quot;Microsoft YaHei&quot;,&quot;PingFang SC&quot;,&quot;Hiragino Sans GB&quot;,&quot;WenQuanYi Micro Hei&quot;; font-size:0.85rem; vertical-align:baseline; background:0px 0px; overflow:auto; color:rgb(211,211,211); line-height:1.3rem; text-align:right">
      
       
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     <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; font-size:13.6px; vertical-align:baseline; line-height:1.3rem">
      
        
       19
      
       
     </div>
      
       
     <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; font-size:13.6px; vertical-align:baseline; line-height:1.3rem">
      
        
       20
      
       
     </div>
      
       
     <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; font-size:13.6px; vertical-align:baseline; line-height:1.3rem">
      
        
       21
      
       
     </div>
      
       
     <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; font-size:13.6px; vertical-align:baseline; line-height:1.3rem">
      
        
       22
      
       
     </div>
      
       
     <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; font-size:13.6px; vertical-align:baseline; line-height:1.3rem">
      
        
       23
      
       
     </div>
      
       
     <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; font-size:13.6px; vertical-align:baseline; line-height:1.3rem">
      
        
       24
      
       
     </div>
      
       
     <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; font-size:13.6px; vertical-align:baseline; line-height:1.3rem">
      
        
       25
      
       
     </div>
      
       
     <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; font-size:13.6px; vertical-align:baseline; line-height:1.3rem">
      
        
       26
      
       
     </div>
      
       
     <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; font-size:13.6px; vertical-align:baseline; line-height:1.3rem">
      
        
       27
      
       
     </div>
      
       
     <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; font-size:13.6px; vertical-align:baseline; line-height:1.3rem">
      
        
       28
      
       
     </div></pre> </td> 
   <td style="margin:0px; padding:0px; border:none; outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> <pre style="margin-top:0px; margin-bottom:0px; padding:0px; border:none; outline:0px; font-weight:inherit; font-style:inherit; font-family:Menlo,Consolas,&quot;Source Code Pro&quot;,Inconsolata,Monaco,monospace,&quot;Microsoft YaHei&quot;,&quot;PingFang SC&quot;,&quot;Hiragino Sans GB&quot;,&quot;WenQuanYi Micro Hei&quot;; font-size:1em; vertical-align:baseline; background:0px 0px; overflow:auto; color:rgb(77,77,76); line-height:1.3rem">
      
       
     <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; line-height:1.3rem">
       
        
      <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; color:rgb(66,113,174)"><span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; color:rgb(137,89,168)">public</span> <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; color:rgb(137,89,168)">static</span> <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; color:rgb(137,89,168)">void</span> <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; color:rgb(142,144,140)">main</span><span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; color:rgb(245,135,31)">(String[] args)</span> <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; color:rgb(137,89,168)">throws</span> Exception </span>{
      
       
     </div>
      
       
     <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; line-height:1.3rem">     
      
       
     </div>
      
       
     <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; line-height:1.3rem">
      
        
           Class&lt;?&gt; clazz = Class.forName(
       
        
      <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; color:rgb(113,140,0)">"org.demo.reflect.bean.People"</span>);
      
       
     </div>
      
       
     <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; line-height:1.3rem">
      
        
           Object instance = clazz.newInstance();
      
       
     </div>
      
       
     <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; line-height:1.3rem">    
       
        
      <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; color:rgb(142,144,140)">// 获取指定的Method</span>
      
       
     </div>
      
       
     <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; line-height:1.3rem">
      
        
           Method m1 = clazz.getMethod(
       
        
      <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; color:rgb(113,140,0)">"say"</span>, String.class, 
       
        
      <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; color:rgb(137,89,168)">int</span>.class);
      
       
     </div>
      
       
     <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; line-height:1.3rem">    
       
        
      <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; color:rgb(142,144,140)">// 获取方法名</span>
      
       
     </div>
      
       
     <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; line-height:1.3rem">
      
        
           System.out.println(m1.getName());
      
       
     </div>
      
       
     <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; line-height:1.3rem">    
       
        
      <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; color:rgb(142,144,140)">// 获取方法的返回值类型</span>
      
       
     </div>
      
       
     <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; line-height:1.3rem">
      
        
           System.out.println(m1.getReturnType());
      
       
     </div>
      
       
     <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; line-height:1.3rem">    
       
        
      <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; color:rgb(142,144,140)">// 获取方法的所有参数类型</span>
      
       
     </div>
      
       
     <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; line-height:1.3rem">
      
        
           Class&lt;?&gt;[] paramsType = m1.getParameterTypes();
      
       
     </div>
      
       
     <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; line-height:1.3rem">    
       
        
      <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; color:rgb(137,89,168)">for</span> (Class&lt;?&gt; c : paramsType) {
      
       
     </div>
      
       
     <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; line-height:1.3rem">
      
        
               System.out.println(c);
      
       
     </div>
      
       
     <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; line-height:1.3rem">
      
        
           }
      
       
     </div>
      
       
     <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; line-height:1.3rem">    
       
        
      <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; color:rgb(142,144,140)">// 获取参数名称（JDK1.8开始支持）</span>
      
       
     </div>
      
       
     <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; line-height:1.3rem">
      
        
           Parameter[] params = m1.getParameters();
      
       
     </div>
      
       
     <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; line-height:1.3rem">    
       
        
      <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; color:rgb(137,89,168)">for</span> (Parameter p : params) {
      
       
     </div>
      
       
     <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; line-height:1.3rem">
      
        
               System.out.println(
       
        
      <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; color:rgb(113,140,0)">"参数类型:"</span>+p.getType());
      
       
     </div>
      
       
     <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; line-height:1.3rem">
      
        
               System.out.println(
       
        
      <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; color:rgb(113,140,0)">"参数名称:"</span>+p.getName());
      
       
     </div>
      
       
     <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; line-height:1.3rem">
      
        
           }
      
       
     </div>
      
       
     <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; line-height:1.3rem">    
       
        
      <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; color:rgb(142,144,140)">// 通过当前的方法，获取定义这个方法的类</span>
      
       
     </div>
      
       
     <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; line-height:1.3rem">
      
        
           Class&lt;?&gt; c = m1.getDeclaringClass();
      
       
     </div>
      
       
     <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; line-height:1.3rem">
      
        
           System.out.println(c.getName());
      
       
     </div>
      
       
     <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; line-height:1.3rem">  
      
       
     </div>
      
       
     <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; line-height:1.3rem">    
       
        
      <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; color:rgb(142,144,140)">// 方法回调，目的就是通过反射去调用一个方法</span>
      
       
     </div>
      
       
     <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; line-height:1.3rem">
      
        
           m1.invoke(instance, 
       
        
      <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; color:rgb(113,140,0)">"godql"</span>, 
       
        
      <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; color:rgb(245,135,31)">21</span>);
      
       
     </div>
      
       
     <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; line-height:1.3rem">
      
        
       }
      
       
     </div></pre> </td> 
  </tr> 
 </tbody> 
</table>

#### 动态操作构造方法 ####

*  Constructor是在反射API中用于封装构造方法的一个类，因此通过这个类可以获取构造方法的一些信息，以及通过这个对象来实例化一个类的实例。
    
    `getConstructor()` // 获取无参并且公共的构造方法  
    `getDeclaredConstructor()` // 获取一个构造方法可以是私有的也可以是公共的，需要传入一个可变参数，就是构造方法的参数类型（注意：如果是私有的，必须先打开访问开关）  
    `newInstance()` // 通过构造方法创建实例，也需要传入一个可变参数，传入的是具体的值  
    `getConstructors()` // 获取所有公共的构造方法，返回的是一个Constructor数组  
    `getDeclaredConstructors()` // 获取所有的构造方法(包括私有和共有的),同样返回的是一个数组  
    `getParameters()` // 获取所有的参数对象，和Method一样  
    `getParameterTypes()` // 获取所有的参数类型，同Method一样

<table style="margin:0px; padding:0px; border:none; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; border-collapse:collapse; border-spacing:0px; width:auto; max-width:65em; empty-cells:show"> 
 <tbody style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline"> 
  <tr style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; height:35px"> 
   <td style="margin:0px; padding:0px; border:none; outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px; white-space:nowrap"> <pre style="margin-top:0px; margin-bottom:0px; padding:0px 1em 0px 0px; border:none; outline:0px; font-weight:inherit; font-style:inherit; font-family:Menlo,Consolas,&quot;Source Code Pro&quot;,Inconsolata,Monaco,monospace,&quot;Microsoft YaHei&quot;,&quot;PingFang SC&quot;,&quot;Hiragino Sans GB&quot;,&quot;WenQuanYi Micro Hei&quot;; font-size:0.85rem; vertical-align:baseline; background:0px 0px; overflow:auto; color:rgb(211,211,211); line-height:1.3rem; text-align:right">
      
       
     <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; font-size:13.6px; vertical-align:baseline; line-height:1.3rem">
      
        
       1
      
       
     </div>
      
       
     <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; font-size:13.6px; vertical-align:baseline; line-height:1.3rem">
      
        
       2
      
       
     </div>
      
       
     <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; font-size:13.6px; vertical-align:baseline; line-height:1.3rem">
      
        
       3
      
       
     </div>
      
       
     <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; font-size:13.6px; vertical-align:baseline; line-height:1.3rem">
      
        
       4
      
       
     </div>
      
       
     <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; font-size:13.6px; vertical-align:baseline; line-height:1.3rem">
      
        
       5
      
       
     </div>
      
       
     <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; font-size:13.6px; vertical-align:baseline; line-height:1.3rem">
      
        
       6
      
       
     </div>
      
       
     <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; font-size:13.6px; vertical-align:baseline; line-height:1.3rem">
      
        
       7
      
       
     </div>
      
       
     <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; font-size:13.6px; vertical-align:baseline; line-height:1.3rem">
      
        
       8
      
       
     </div>
      
       
     <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; font-size:13.6px; vertical-align:baseline; line-height:1.3rem">
      
        
       9
      
       
     </div>
      
       
     <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; font-size:13.6px; vertical-align:baseline; line-height:1.3rem">
      
        
       10
      
       
     </div>
      
       
     <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; font-size:13.6px; vertical-align:baseline; line-height:1.3rem">
      
        
       11
      
       
     </div>
      
       
     <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; font-size:13.6px; vertical-align:baseline; line-height:1.3rem">
      
        
       12
      
       
     </div>
      
       
     <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; font-size:13.6px; vertical-align:baseline; line-height:1.3rem">
      
        
       13
      
       
     </div>
      
       
     <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; font-size:13.6px; vertical-align:baseline; line-height:1.3rem">
      
        
       14
      
       
     </div>
      
       
     <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; font-size:13.6px; vertical-align:baseline; line-height:1.3rem">
      
        
       15
      
       
     </div>
      
       
     <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; font-size:13.6px; vertical-align:baseline; line-height:1.3rem">
      
        
       16
      
       
     </div>
      
       
     <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; font-size:13.6px; vertical-align:baseline; line-height:1.3rem">
      
        
       17
      
       
     </div>
      
       
     <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; font-size:13.6px; vertical-align:baseline; line-height:1.3rem">
      
        
       18
      
       
     </div>
      
       
     <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; font-size:13.6px; vertical-align:baseline; line-height:1.3rem">
      
        
       19
      
       
     </div>
      
       
     <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; font-size:13.6px; vertical-align:baseline; line-height:1.3rem">
      
        
       20
      
       
     </div>
      
       
     <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; font-size:13.6px; vertical-align:baseline; line-height:1.3rem">
      
        
       21
      
       
     </div>
      
       
     <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; font-size:13.6px; vertical-align:baseline; line-height:1.3rem">
      
        
       22
      
       
     </div>
      
       
     <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; font-size:13.6px; vertical-align:baseline; line-height:1.3rem">
      
        
       23
      
       
     </div>
      
       
     <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; font-size:13.6px; vertical-align:baseline; line-height:1.3rem">
      
        
       24
      
       
     </div>
      
       
     <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; font-size:13.6px; vertical-align:baseline; line-height:1.3rem">
      
        
       25
      
       
     </div>
      
       
     <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; font-size:13.6px; vertical-align:baseline; line-height:1.3rem">
      
        
       26
      
       
     </div>
      
       
     <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; font-size:13.6px; vertical-align:baseline; line-height:1.3rem">
      
        
       27
      
       
     </div>
      
       
     <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; font-size:13.6px; vertical-align:baseline; line-height:1.3rem">
      
        
       28
      
       
     </div>
      
       
     <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; font-size:13.6px; vertical-align:baseline; line-height:1.3rem">
      
        
       29
      
       
     </div>
      
       
     <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; font-size:13.6px; vertical-align:baseline; line-height:1.3rem">
      
        
       30
      
       
     </div>
      
       
     <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; font-size:13.6px; vertical-align:baseline; line-height:1.3rem">
      
        
       31
      
       
     </div>
      
       
     <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; font-size:13.6px; vertical-align:baseline; line-height:1.3rem">
      
        
       32
      
       
     </div>
      
       
     <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; font-size:13.6px; vertical-align:baseline; line-height:1.3rem">
      
        
       33
      
       
     </div></pre> </td> 
   <td style="margin:0px; padding:0px; border:none; outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> <pre style="margin-top:0px; margin-bottom:0px; padding:0px; border:none; outline:0px; font-weight:inherit; font-style:inherit; font-family:Menlo,Consolas,&quot;Source Code Pro&quot;,Inconsolata,Monaco,monospace,&quot;Microsoft YaHei&quot;,&quot;PingFang SC&quot;,&quot;Hiragino Sans GB&quot;,&quot;WenQuanYi Micro Hei&quot;; font-size:1em; vertical-align:baseline; background:0px 0px; overflow:auto; color:rgb(77,77,76); line-height:1.3rem">
      
       
     <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; line-height:1.3rem">
       
        
      <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; color:rgb(66,113,174)"><span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; color:rgb(137,89,168)">public</span> <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; color:rgb(137,89,168)">static</span> <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; color:rgb(137,89,168)">void</span> <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; color:rgb(142,144,140)">main</span><span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; color:rgb(245,135,31)">(String[] args)</span> <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; color:rgb(137,89,168)">throws</span> Exception </span>{
      
       
     </div>
      
       
     <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; line-height:1.3rem">      
      
       
     </div>
      
       
     <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; line-height:1.3rem">
      
        
           Class&lt;?&gt; clazz = People.class;
      
       
     </div>
      
       
     <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; line-height:1.3rem">    
       
        
      <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; color:rgb(142,144,140)">// 获取无参的构造方法</span>
      
       
     </div>
      
       
     <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; line-height:1.3rem">
      
        
           Constructor&lt;?&gt; c1 = clazz.getConstructor();
      
       
     </div>
      
       
     <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; line-height:1.3rem">    
       
        
      <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; color:rgb(142,144,140)">// 获取构造方法的名称</span>
      
       
     </div>
      
       
     <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; line-height:1.3rem">
      
        
           System.out.println(c1.getName());
      
       
     </div>
      
       
     <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; line-height:1.3rem">    
       
        
      <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; color:rgb(142,144,140)">// 获取一个私有并且带参数的构造方法</span>
      
       
     </div>
      
       
     <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; line-height:1.3rem">
      
        
           Constructor&lt;?&gt; c2 = clazz.getDeclaredConstructor(String.class);
      
       
     </div>
      
       
     <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; line-height:1.3rem">  
      
       
     </div>
      
       
     <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; line-height:1.3rem">    
       
        
      <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; color:rgb(142,144,140)">// 可以通过构造方法实例化一个对象</span>
      
       
     </div>
      
       
     <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; line-height:1.3rem">    
       
        
      <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; color:rgb(142,144,140)">//（注意：如果默认有一个无参并且是公共的构造方法，</span>
      
       
     </div>
      
       
     <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; line-height:1.3rem">    
       
        
      <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; color:rgb(142,144,140)">// 那么可以直接使用class.newInstance()方法创建实例，</span>
      
       
     </div>
      
       
     <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; line-height:1.3rem">    
       
        
      <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; color:rgb(142,144,140)">// 如果构造方法是私有的，或者是带参数的，就必须先获取</span>
      
       
     </div>
      
       
     <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; line-height:1.3rem">    
       
        
      <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; color:rgb(142,144,140)">// Constructor对象，在通过这个对象来创建类实例）</span>
      
       
     </div>
      
       
     <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; line-height:1.3rem">  
      
       
     </div>
      
       
     <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; line-height:1.3rem">    
       
        
      <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; color:rgb(142,144,140)">// 1.适用于无参并且是公共的构造方法</span>
      
       
     </div>
      
       
     <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; line-height:1.3rem">    
       
        
      <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; color:rgb(142,144,140)">/* </span>
      
       
     </div>
      
       
     <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; line-height:1.3rem">
      
        
             Object instance = clazz.newInstance();
      
       
     </div>
      
       
     <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; line-height:1.3rem">
      
        
             System.out.println(instance);
      
       
     </div>
      
       
     <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; line-height:1.3rem">
      
        
           */
      
       
     </div>
      
       
     <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; line-height:1.3rem">  
      
       
     </div>
      
       
     <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; line-height:1.3rem">    
       
        
      <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; color:rgb(142,144,140)">// 2.适用于带参数或是私有的构造方法</span>
      
       
     </div>
      
       
     <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; line-height:1.3rem">    
       
        
      <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; color:rgb(142,144,140)">// 由于构造方法也可以私有化，所以必须先打开访问开关</span>
      
       
     </div>
      
       
     <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; line-height:1.3rem">
      
        
           c2.setAccessible(
       
        
      <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; color:rgb(137,89,168)">true</span>);
      
       
     </div>
      
       
     <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; line-height:1.3rem">
      
        
           Object instance = c2.newInstance(
       
        
      <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; color:rgb(113,140,0)">"godql"</span>);
      
       
     </div>
      
       
     <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; line-height:1.3rem">
      
        
           System.out.println(instance);
      
       
     </div>
      
       
     <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; line-height:1.3rem">  
      
       
     </div>
      
       
     <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; line-height:1.3rem">    
       
        
      <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; color:rgb(142,144,140)">// 获取所有public修饰的构造方法</span>
      
       
     </div>
      
       
     <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; line-height:1.3rem">
      
        
           Constructor&lt;?&gt;[] cons = clazz.getConstructors();
      
       
     </div>
      
       
     <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; line-height:1.3rem">    
       
        
      <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; color:rgb(142,144,140)">// 获取所有构造方法（包括私有的）</span>
      
       
     </div>
      
       
     <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; line-height:1.3rem">
      
        
           Constructor&lt;?&gt;[] cons2 = clazz.getDeclaredConstructors();
      
       
     </div>
      
       
     <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; line-height:1.3rem">
      
        
       }
      
       
     </div></pre> </td> 
  </tr> 
 </tbody> 
</table>

#### Class中的一些API ####

*  Class对象本身提供了很多的API方法用于获取和操作Class对象。
    
    `getPackage()` // 获取当前类所在的包，使用Package对象进行封装，可以从中获取包的信息，例如：包名  
    `getSimpleName()` // 获取当前类的简单类名（不包括包名）  
    `getName()` // 获取当前类的完整类名(包括包名)  
    `getSuperclass()` // 获取当前类的父类，返回的也是一个Class对象  
    `getInterfaces()` // 获取当前类所实现的所有接口，返回的是一个Class数组  
    `isAnnotationPresent()` // 判断当前类上是否定义了注解  
    `getAnnotation()` // 获取类上定义的注解

### 通过反射了解集合泛型的本质 ###

*  Java中集合的泛型，是防止错误输入的，只在编译阶段有效，绕过编译到了运行期就无效了。
    
    <table style="margin:0px; padding:0px; border:none; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; border-collapse:collapse; border-spacing:0px; width:auto; max-width:65em; empty-cells:show"> 
     <tbody style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline"> 
      <tr style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; height:35px"> 
       <td style="margin:0px; padding:0px; border:none; outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px; white-space:nowrap"> <pre style="margin-top:0px; margin-bottom:0px; padding:0px 1em 0px 0px; border:none; outline:0px; font-weight:inherit; font-style:inherit; font-family:Menlo,Consolas,&quot;Source Code Pro&quot;,Inconsolata,Monaco,monospace,&quot;Microsoft YaHei&quot;,&quot;PingFang SC&quot;,&quot;Hiragino Sans GB&quot;,&quot;WenQuanYi Micro Hei&quot;; font-size:0.85rem; vertical-align:baseline; background:0px 0px; overflow:auto; color:rgb(211,211,211); line-height:1.3rem; text-align:right">
            
             
         <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; font-size:13.6px; vertical-align:baseline; line-height:1.3rem">
          
              
             1
            
             
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         <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; font-size:13.6px; vertical-align:baseline; line-height:1.3rem">
          
              
             2
            
             
         </div>
            
             
         <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; font-size:13.6px; vertical-align:baseline; line-height:1.3rem">
          
              
             3
            
             
         </div>
            
             
         <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; font-size:13.6px; vertical-align:baseline; line-height:1.3rem">
          
              
             4
            
             
         </div>
            
             
         <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; font-size:13.6px; vertical-align:baseline; line-height:1.3rem">
          
              
             5
            
             
         </div>
            
             
         <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; font-size:13.6px; vertical-align:baseline; line-height:1.3rem">
          
              
             6
            
             
         </div>
            
             
         <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; font-size:13.6px; vertical-align:baseline; line-height:1.3rem">
          
              
             7
            
             
         </div>
            
             
         <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; font-size:13.6px; vertical-align:baseline; line-height:1.3rem">
          
              
             8
            
             
         </div>
            
             
         <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; font-size:13.6px; vertical-align:baseline; line-height:1.3rem">
          
              
             9
            
             
         </div>
            
             
         <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; font-size:13.6px; vertical-align:baseline; line-height:1.3rem">
          
              
             10
            
             
         </div>
            
             
         <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; font-size:13.6px; vertical-align:baseline; line-height:1.3rem">
          
              
             11
            
             
         </div>
            
             
         <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; font-size:13.6px; vertical-align:baseline; line-height:1.3rem">
          
              
             12
            
             
         </div>
            
             
         <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; font-size:13.6px; vertical-align:baseline; line-height:1.3rem">
          
              
             13
            
             
         </div>
            
             
         <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; font-size:13.6px; vertical-align:baseline; line-height:1.3rem">
          
              
             14
            
             
         </div>
            
             
         <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; font-size:13.6px; vertical-align:baseline; line-height:1.3rem">
          
              
             15
            
             
         </div>
            
             
         <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; font-size:13.6px; vertical-align:baseline; line-height:1.3rem">
          
              
             16
            
             
         </div>
            
             
         <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; font-size:13.6px; vertical-align:baseline; line-height:1.3rem">
          
              
             17
            
             
         </div>
            
             
         <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; font-size:13.6px; vertical-align:baseline; line-height:1.3rem">
          
              
             18
            
             
         </div>
            
             
         <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; font-size:13.6px; vertical-align:baseline; line-height:1.3rem">
          
              
             19
            
             
         </div>
            
             
         <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; font-size:13.6px; vertical-align:baseline; line-height:1.3rem">
          
              
             20
            
             
         </div>
            
             
         <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; font-size:13.6px; vertical-align:baseline; line-height:1.3rem">
          
              
             21
            
             
         </div>
            
             
         <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; font-size:13.6px; vertical-align:baseline; line-height:1.3rem">
          
              
             22
            
             
         </div>
            
             
         <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; font-size:13.6px; vertical-align:baseline; line-height:1.3rem">
          
              
             23
            
             
         </div>
            
             
         <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; font-size:13.6px; vertical-align:baseline; line-height:1.3rem">
          
              
             24
            
             
         </div>
            
             
         <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; font-size:13.6px; vertical-align:baseline; line-height:1.3rem">
          
              
             25
            
             
         </div>
            
             
         <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; font-size:13.6px; vertical-align:baseline; line-height:1.3rem">
          
              
             26
            
             
         </div>
            
             
         <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; font-size:13.6px; vertical-align:baseline; line-height:1.3rem">
          
              
             27
            
             
         </div>
            
             
         <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; font-size:13.6px; vertical-align:baseline; line-height:1.3rem">
          
              
             28
            
             
         </div>
            
             
         <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; font-size:13.6px; vertical-align:baseline; line-height:1.3rem">
          
              
             29
            
             
         </div>
            
             
         <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; font-size:13.6px; vertical-align:baseline; line-height:1.3rem">
          
              
             30
            
             
         </div>
            
             
         <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; font-size:13.6px; vertical-align:baseline; line-height:1.3rem">
          
              
             31
            
             
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         <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; font-size:13.6px; vertical-align:baseline; line-height:1.3rem">
          
              
             32
            
             
         </div>
            
             
         <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; font-size:13.6px; vertical-align:baseline; line-height:1.3rem">
          
              
             33
            
             
         </div>
            
             
         <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; font-size:13.6px; vertical-align:baseline; line-height:1.3rem">
          
              
             34
            
             
         </div></pre> </td> 
       <td style="margin:0px; padding:0px; border:none; outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> <pre style="margin-top:0px; margin-bottom:0px; padding:0px; border:none; outline:0px; font-weight:inherit; font-style:inherit; font-family:Menlo,Consolas,&quot;Source Code Pro&quot;,Inconsolata,Monaco,monospace,&quot;Microsoft YaHei&quot;,&quot;PingFang SC&quot;,&quot;Hiragino Sans GB&quot;,&quot;WenQuanYi Micro Hei&quot;; font-size:1em; vertical-align:baseline; background:0px 0px; overflow:auto; color:rgb(77,77,76); line-height:1.3rem">
            
             
         <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; line-height:1.3rem">
             
              
          <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; color:rgb(66,113,174)"><span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; color:rgb(137,89,168)">public</span> <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; color:rgb(137,89,168)">static</span> <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; color:rgb(137,89,168)">void</span> <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; color:rgb(142,144,140)">main</span><span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; color:rgb(245,135,31)">(String[] args)</span> </span>{
            
             
         </div>
            
             
         <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; line-height:1.3rem">     
            
             
         </div>
            
             
         <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; line-height:1.3rem">
          
              
                 List list = 
             
              
          <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; color:rgb(137,89,168)">new</span> ArrayList(); 
            
             
         </div>
            
             
         <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; line-height:1.3rem">
          
              
                 List&lt;String&gt; list1 = 
             
              
          <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; color:rgb(137,89,168)">new</span> ArrayList&lt;&gt;(); 
            
             
         </div>
            
             
         <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; line-height:1.3rem">   
            
             
         </div>
            
             
         <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; line-height:1.3rem">
          
              
                 list.add(
             
              
          <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; color:rgb(113,140,0)">"godql"</span>);
            
             
         </div>
            
             
         <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; line-height:1.3rem">    
             
              
          <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; color:rgb(142,144,140)">// list1.add(20); 错误的</span>
            
             
         </div>
            
             
         <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; line-height:1.3rem"></div>
            
             
         <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; line-height:1.3rem">
          
              
                 Class c1 = list.getClass();
            
             
         </div>
            
             
         <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; line-height:1.3rem">
          
              
                 Class c2 = list1.getClass();
            
             
         </div>
            
             
         <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; line-height:1.3rem">   
            
             
         </div>
            
             
         <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; line-height:1.3rem">
          
              
                 System.out.println(c1 == c2); 
             
              
          <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; color:rgb(142,144,140)">// 结果：true，说明类类型完全相同</span>
            
             
         </div>
            
             
         <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; line-height:1.3rem">    
             
              
          <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; color:rgb(142,144,140)">// 反射的操作都是编译之后的操作(运行时)</span>
            
             
         </div>
            
             
         <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; line-height:1.3rem">   
            
             
         </div>
            
             
         <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; line-height:1.3rem">    
             
              
          <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; color:rgb(142,144,140)">/*</span>
            
             
         </div>
            
             
         <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; line-height:1.3rem">
          
              
                  * 以上说明编译之后集合的泛型是泛型擦除的
            
             
         </div>
            
             
         <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; line-height:1.3rem">
          
              
                  * Java中集合的泛型，是防止错误输入的，只在编译阶段有效，绕过编译就无效了。
            
             
         </div>
            
             
         <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; line-height:1.3rem">
          
              
                  * 验证: 通过方法的反射来操作，绕过编译 
            
             
         </div>
            
             
         <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; line-height:1.3rem">
          
              
                  */
            
             
         </div>
            
             
         <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; line-height:1.3rem">    
             
              
          <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; color:rgb(137,89,168)">try</span> {
            
             
         </div>
            
             
         <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; line-height:1.3rem">        
             
              
          <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; color:rgb(142,144,140)">// 通过动态操作方法的反射得到add方法</span>
            
             
         </div>
            
             
         <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; line-height:1.3rem">
          
              
                     Method m = c2.getMethod(
             
              
          <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; color:rgb(113,140,0)">"add"</span>, Object.class);
            
             
         </div>
            
             
         <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; line-height:1.3rem">        
             
              
          <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; color:rgb(142,144,140)">// 方法回调 给list1添加一个int型的，这是在运行时的操作，所以编译器编译时没有泛型检查，所以不会报错</span>
            
             
         </div>
            
             
         <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; line-height:1.3rem">        
             
              
          <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; color:rgb(142,144,140)">// 绕过编译操作</span>
            
             
         </div>
            
             
         <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; line-height:1.3rem">
          
              
                     m.invoke(list1, 
             
              
          <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; color:rgb(245,135,31)">20</span>);
            
             
         </div>
            
             
         <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; line-height:1.3rem">        
             
              
          <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; color:rgb(142,144,140)">// 验证是否有添加进list集合里</span>
            
             
         </div>
            
             
         <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; line-height:1.3rem">
          
              
                     System.out.println(list1.size()); 
            
             
         </div>
            
             
         <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; line-height:1.3rem">        
             
              
          <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; color:rgb(142,144,140)">// 这时候不能使用foreach遍历，否则集合会认为集合里边全是String类型的值</span>
            
             
         </div>
            
             
         <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; line-height:1.3rem">        
             
              
          <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; color:rgb(142,144,140)">// 且有类型转换错误，因为这个集合里面有int类型、String类</span>
            
             
         </div>
            
             
         <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; line-height:1.3rem">
          
              
                     System.out.println(list1); 
            
             
         </div>
            
             
         <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; line-height:1.3rem">
          
              
                 } 
             
              
          <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; color:rgb(137,89,168)">catch</span> (Exception e) {
            
             
         </div>
            
             
         <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; line-height:1.3rem">
          
              
                        e.printStackTrace();
            
             
         </div>
            
             
         <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; line-height:1.3rem">
          
              
                 }
            
             
         </div>
            
             
         <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; line-height:1.3rem">
          
              
             }
            
             
         </div></pre> </td> 
      </tr> 
     </tbody> 
    </table>

### 使用场景 ###

*  通用的应用程序
 *  框架比如：  
    　　　1.Spring 的 Ioc/Di  
    　　　2.SpringMVC 监控 Controller中的注解  
    　　　3.MyBatis 利用反射获取和设置对象值  
    　　　4.Struts2 的 FormBean 和页面之间…  
    　　　5.Hibernate的 find(Class clazz)  
    　　　6.JavaBean和JSP之间调用  
    　　　7.JDBC 的 classForName()

### 源码下载 ###

[GitHub][]

[E5_8F_8C_E4_BA_B2_E5_A7_94_E6_89_98_E6_9C_BA_E5_88_B6.png]: http://oo31b5ljj.bkt.clouddn.com/%E5%8F%8C%E4%BA%B2%E5%A7%94%E6%89%98%E6%9C%BA%E5%88%B6.png
[E9_80_92_E5_BD_92_E6_A0_88.png]: http://oo31b5ljj.bkt.clouddn.com/%E9%80%92%E5%BD%92%E6%A0%88.png
[E6_9C_AC_E5_9C_B0_E6_96_B9_E6_B3_95_E6_A0_881.png]: http://oo31b5ljj.bkt.clouddn.com/%E6%9C%AC%E5%9C%B0%E6%96%B9%E6%B3%95%E6%A0%881.png
[E5_A0_86_EF_BC_9A_E5_BC_95_E7_94_A8.png]: http://oo31b5ljj.bkt.clouddn.com/%E5%A0%86%EF%BC%9A%E5%BC%95%E7%94%A8.png
[E5_A0_86_EF_BC_9A_E5_AF_B9_E8_B1_A1_E6_9B_B4_E6_94_B9.png]: http://oo31b5ljj.bkt.clouddn.com/%E5%A0%86%EF%BC%9A%E5%AF%B9%E8%B1%A1%E6%9B%B4%E6%94%B9.png
[E5_A0_86_EF_BC_9A_E6_95_B0_E7_BB_84.png]: http://oo31b5ljj.bkt.clouddn.com/%E5%A0%86%EF%BC%9A%E6%95%B0%E7%BB%84.png
[E5_A0_86_EF_BC_9A_E5_BE_AA_E7_8E_AF.png]: http://oo31b5ljj.bkt.clouddn.com/%E5%A0%86%EF%BC%9A%E5%BE%AA%E7%8E%AF.png
[E6_96_B9_E6_B3_95_E5_8C_BA.png]: http://oo31b5ljj.bkt.clouddn.com/%E6%96%B9%E6%B3%95%E5%8C%BA.png
[E5_B8_B8_E9_87_8F_E6_B1_A0.jpg]: http://oo31b5ljj.bkt.clouddn.com/%E5%B8%B8%E9%87%8F%E6%B1%A0.jpg
[E5_86_85_E5_AD_98_E8_BF_90_E8_A1_8C_E6_97_B6_E6_95_B0_E6_8D_AE_E5_8C_BA.png]: http://oo31b5ljj.bkt.clouddn.com/%E5%86%85%E5%AD%98%E8%BF%90%E8%A1%8C%E6%97%B6%E6%95%B0%E6%8D%AE%E5%8C%BA.png
[String]: http://oo31b5ljj.bkt.clouddn.com/String%E7%B1%BB%E5%8A%A0%E8%BD%BD%E7%A4%BA%E6%84%8F%E5%9B%BE.png
[GitHub]: https://github.com/GitHubSupervise/JavaSE-Learning-Summary