线程管理之线程创建和运行

缺乏、安全感 2023-10-16 21:54 15阅读 0赞

在学习Java7并发编程实战手册之前，我们必须先搞清楚一个问题：什么叫并行，什么又叫并发？

以下图片是我对并行和并发的个人理解，欢迎大家指教。

![Center][]

现在开始，进入我们今天的主体“线程的创建和运行”

Java提供两种方式创建线程：

1、继承Thread类，并且覆盖run方法。

2、创建一个实现Runnable接口的类，使用带参数的Threaded构造器来创建Thread对象。这个参数就是实现Runnable 接口类的对象。

在这个指南中，我们将使用第二种方法来制作一个简单的程序，它能创建和运行10个线程。每一个线程能计算和输出1-10以内的乘法表。

准备   
指南中的例子是使用Eclipse IDE 来实现的。如果你使用Eclipse 或者其他的IDE，例如NetBeans, 打开并创建一个新的java项目。

怎么做呢**…**

按照这些步骤来实现下面的例子：

1. 创建一个名为Calculator的类，这个类要实现Runnable接口。

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   <td style="border:0px!important; padding:0px!important; margin:0px!important; outline:0px!important; float:none!important; vertical-align:top!important; position:static!important; left:auto!important; top:auto!important; right:auto!important; bottom:auto!important; height:auto!important; width:3em!important; line-height:1.1em!important; font-family:Consolas,'Bitstream Vera Sans Mono','Courier New',Courier,monospace!important; font-size:1em!important; direction:ltr!important; color:rgb(120,120,120)!important"> <code style="margin:0px!important; padding:0px 0.3em 0px 0px!important; border:0px!important; outline:0px!important; text-align:right!important; float:none!important; vertical-align:baseline!important; position:static!important; left:auto!important; top:auto!important; right:auto!important; bottom:auto!important; height:auto!important; width:2.7em!important; line-height:1.1em!important; font-family:Consolas,'Bitstream Vera Sans Mono','Courier New',Courier,monospace!important; font-size:1em!important; direction:ltr!important; display:block!important; background:none!important">1</code></td> 
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  </tr> 
 </tbody> 
</table>

2. 声明一个名为number 的private int为属性，然后实现构造函数并初始化其值。

3. 实现run()方法. 这方法是给我们创建的线程执行指令，所以这个方法将计算数字乘法表。

4. 现在, 实现程序的Main类。创建一个名为 Main的类并包含 main() 方法.

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   <td style="border-width:0px 0px 0px 1px!important; border-left-style:solid!important; border-left-color:rgb(212,208,200)!important; padding:0px 0px 0px 0.5em!important; margin:0px!important; outline:0px!important; float:none!important; vertical-align:top!important; position:static!important; left:auto!important; top:auto!important; right:auto!important; bottom:auto!important; height:auto!important; width:auto!important; line-height:1.1em!important; font-family:Consolas,'Bitstream Vera Sans Mono','Courier New',Courier,monospace!important; font-size:1em!important; direction:ltr!important; background:none!important"> <code style="margin:0px!important; padding:0px!important; border:0px!important; outline:0px!important; float:none!important; vertical-align:baseline!important; position:static!important; left:auto!important; top:auto!important; right:auto!important; bottom:auto!important; height:auto!important; width:auto!important; line-height:1.1em!important; font-family:Consolas,'Bitstream Vera Sans Mono','Courier New',Courier,monospace!important; font-size:1em!important; direction:ltr!important; display:inline!important; background:none!important">&nbsp;&nbsp;&nbsp;&nbsp;</code><code style="margin:0px!important; padding:0px!important; border:0px!important; outline:0px!important; float:none!important; vertical-align:baseline!important; position:static!important; left:auto!important; top:auto!important; right:auto!important; bottom:auto!important; height:auto!important; width:auto!important; line-height:1.1em!important; font-family:Consolas,'Bitstream Vera Sans Mono','Courier New',Courier,monospace!important; font-weight:bold!important; font-size:1em!important; direction:ltr!important; display:inline!important; color:rgb(127,0,85)!important; background:none!important">public</code>&nbsp;<code style="margin:0px!important; padding:0px!important; border:0px!important; outline:0px!important; float:none!important; vertical-align:baseline!important; position:static!important; left:auto!important; top:auto!important; right:auto!important; bottom:auto!important; height:auto!important; width:auto!important; line-height:1.1em!important; font-family:Consolas,'Bitstream Vera Sans Mono','Courier New',Courier,monospace!important; font-weight:bold!important; font-size:1em!important; direction:ltr!important; display:inline!important; color:rgb(127,0,85)!important; background:none!important">static</code>&nbsp;<code style="margin:0px!important; padding:0px!important; border:0px!important; outline:0px!important; float:none!important; vertical-align:baseline!important; position:static!important; left:auto!important; top:auto!important; right:auto!important; bottom:auto!important; height:auto!important; width:auto!important; line-height:1.1em!important; font-family:Consolas,'Bitstream Vera Sans Mono','Courier New',Courier,monospace!important; font-weight:bold!important; font-size:1em!important; direction:ltr!important; display:inline!important; color:rgb(127,0,85)!important; background:none!important">void</code>&nbsp;<code style="margin:0px!important; padding:0px!important; border:0px!important; outline:0px!important; float:none!important; vertical-align:baseline!important; position:static!important; left:auto!important; top:auto!important; right:auto!important; bottom:auto!important; height:auto!important; width:auto!important; line-height:1.1em!important; font-family:Consolas,'Bitstream Vera Sans Mono','Courier New',Courier,monospace!important; font-size:1em!important; direction:ltr!important; display:inline!important; background:none!important">main(String[] args) { </code></td> 
  </tr> 
 </tbody> 
</table>

5. 在 main() 方法内，创建一个迭代10次的for循环。在每次循环中，创建一个 Calculator 类的对象, 一个Thread类的对象, 然后传递 Calculator 对象作为thread类构造函数的参数，最后调用线程对象的start() 方法。

<table style="margin:0px!important; padding:0px!important; border-collapse:collapse!important; width:auto!important; border:0px!important; outline:0px!important; float:none!important; vertical-align:baseline!important; position:static!important; left:auto!important; top:auto!important; right:auto!important; bottom:auto!important; height:auto!important; line-height:1.1em!important; font-size:1em!important; direction:ltr!important; background:none!important"> 
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   <td style="border:0px!important; padding:0px!important; margin:0px!important; outline:0px!important; float:none!important; vertical-align:top!important; position:static!important; left:auto!important; top:auto!important; right:auto!important; bottom:auto!important; height:auto!important; width:3em!important; line-height:1.1em!important; font-family:Consolas,'Bitstream Vera Sans Mono','Courier New',Courier,monospace!important; font-size:1em!important; direction:ltr!important; color:rgb(120,120,120)!important"> <code style="margin:0px!important; padding:0px 0.3em 0px 0px!important; border:0px!important; outline:0px!important; text-align:right!important; float:none!important; vertical-align:baseline!important; position:static!important; left:auto!important; top:auto!important; right:auto!important; bottom:auto!important; height:auto!important; width:2.7em!important; line-height:1.1em!important; font-family:Consolas,'Bitstream Vera Sans Mono','Courier New',Courier,monospace!important; font-size:1em!important; direction:ltr!important; display:block!important; background:none!important">2</code></td> 
   <td style="border-width:0px 0px 0px 1px!important; border-left-style:solid!important; border-left-color:rgb(212,208,200)!important; padding:0px 0px 0px 0.5em!important; margin:0px!important; outline:0px!important; float:none!important; vertical-align:top!important; position:static!important; left:auto!important; top:auto!important; right:auto!important; bottom:auto!important; height:auto!important; width:auto!important; line-height:1.1em!important; font-family:Consolas,'Bitstream Vera Sans Mono','Courier New',Courier,monospace!important; font-size:1em!important; direction:ltr!important; background:none!important"> <code style="margin:0px!important; padding:0px!important; border:0px!important; outline:0px!important; float:none!important; vertical-align:baseline!important; position:static!important; left:auto!important; top:auto!important; right:auto!important; bottom:auto!important; height:auto!important; width:auto!important; line-height:1.1em!important; font-family:Consolas,'Bitstream Vera Sans Mono','Courier New',Courier,monospace!important; font-size:1em!important; direction:ltr!important; display:inline!important; background:none!important">&nbsp;&nbsp;&nbsp;</code><code style="margin:0px!important; padding:0px!important; border:0px!important; outline:0px!important; float:none!important; vertical-align:baseline!important; position:static!important; left:auto!important; top:auto!important; right:auto!important; bottom:auto!important; height:auto!important; width:auto!important; line-height:1.1em!important; font-family:Consolas,'Bitstream Vera Sans Mono','Courier New',Courier,monospace!important; font-size:1em!important; direction:ltr!important; display:inline!important; background:none!important">Calculator calculator=</code><code style="margin:0px!important; padding:0px!important; border:0px!important; outline:0px!important; float:none!important; vertical-align:baseline!important; position:static!important; left:auto!important; top:auto!important; right:auto!important; bottom:auto!important; height:auto!important; width:auto!important; line-height:1.1em!important; font-family:Consolas,'Bitstream Vera Sans Mono','Courier New',Courier,monospace!important; font-weight:bold!important; font-size:1em!important; direction:ltr!important; display:inline!important; color:rgb(127,0,85)!important; background:none!important">new</code>&nbsp;<code style="margin:0px!important; padding:0px!important; border:0px!important; outline:0px!important; float:none!important; vertical-align:baseline!important; position:static!important; left:auto!important; top:auto!important; right:auto!important; bottom:auto!important; height:auto!important; width:auto!important; line-height:1.1em!important; font-family:Consolas,'Bitstream Vera Sans Mono','Courier New',Courier,monospace!important; font-size:1em!important; direction:ltr!important; display:inline!important; background:none!important">Calculator(i); Thread thread=</code><code style="margin:0px!important; padding:0px!important; border:0px!important; outline:0px!important; float:none!important; vertical-align:baseline!important; position:static!important; left:auto!important; top:auto!important; right:auto!important; bottom:auto!important; height:auto!important; width:auto!important; line-height:1.1em!important; font-family:Consolas,'Bitstream Vera Sans Mono','Courier New',Courier,monospace!important; font-weight:bold!important; font-size:1em!important; direction:ltr!important; display:inline!important; color:rgb(127,0,85)!important; background:none!important">new</code>&nbsp;<code style="margin:0px!important; padding:0px!important; border:0px!important; outline:0px!important; float:none!important; vertical-align:baseline!important; position:static!important; left:auto!important; top:auto!important; right:auto!important; bottom:auto!important; height:auto!important; width:auto!important; line-height:1.1em!important; font-family:Consolas,'Bitstream Vera Sans Mono','Courier New',Courier,monospace!important; font-size:1em!important; direction:ltr!important; display:inline!important; background:none!important">Thread(calculator);</code></td> 
  </tr> 
 </tbody> 
</table>

6. 运行程序并观察不同的线程是如何并行工作的。

**它是怎么工作的…**

接下来是部分的程序输出的裁图。我们可以查看全部创建的线程，并行地运行， 见下图：

![Center 1][]

每个Java程序最少有一个执行线程。当你运行程序的时候, JVM运行负责调用main()方法的执行线程。

当调用Thread对象的start()方法时, 我们创建了另一个执行线程。在这些start()方法调出后，我们的程序就有了多个执行线程。

当全部的线程执行结束时（更具体点，所有非守护线程结束时），Java程序就结束了。如果初始线程（执行main()方法的主线程）运行结束，其他的线程还是会继续执行直到执行完成。但是如果某个线程调用System.exit()指示终结程序，那么全部的线程都会结束执行。

创建一个Thread类的对象不会创建新的执行线程。同样，调用实现Runnable接口的 run()方法也不会创建一个新的执行线程。只有调用start()方法才能创建一个新的执行线程。