java反射练习

爱被打了一巴掌 2022-07-12 04:40 180阅读 0赞

public class mytest {
    	public mytest(){}
    	public mytest(int k,String s,boolean b,double d){
    		a=k;
    		c=d;
    		this.s=b;
    		System.out.println("k="+k+",s="+s+",b="+b+",d="+d);
    	}
    	private static final String str="'";
    	public  int a;
    	private double c;
    	private boolean s;
    	private List<String> list;
    	private Map<String,String> map;
    	public static void main(String[] args) {
    		test10();
    	}
    	
    	/**
    	 * 获取类的方法
    	 * */
    	public static void test1(){
    		try{
    			Class c=Class.forName("java.util.Stack");
    			Method m[]=c.getDeclaredMethods();//方法
    			for(int i=0;i<m.length;i++){
    				System.out.println(m[i].toString());
    			}
    		}catch(Exception e){
    			e.printStackTrace();
    		}
    	}
    	/**
    	 * 判断类型
    	 * */
    	public static void test2(){
    		try{
    			Class cls=Class.forName("com.hch.mytest");
    			boolean b1=cls.isInstance(new Integer(2));
    			System.out.println(b1);
    			boolean b2=cls.isInstance(new com.hch.mytest());
    			System.out.println(b2);
    		}catch(Exception e){
    			e.printStackTrace();
    		}
    	}
    	/**
    	 * 获取方法名，返回类型，参数等
    	 * */
    	public static void test3(){
    		try{
    			Class cls=Class.forName("com.hch.reflection.mytest");
    		    Method methlist[]=cls.getDeclaredMethods();
    		    for(int i=0;i<methlist.length;i++){
    		    	Method m=methlist[i];
    		    	System.out.println("name="+m.getName());
    		    	System.out.println("decl class="+m.getDeclaringClass());
    		    	Class pvec[]=m.getParameterTypes();
    		    	for(int j=0;j<pvec.length;j++){
    		    		System.out.println("param #"+j+":"+pvec[j]);
    		    	}
    		    	Class evec[]=m.getExceptionTypes();
    		    	for(int j=0;j<evec.length;j++){
    		    		System.out.println("exc #"+j+":"+evec[j]);
    		    	}
    		    	System.out.println("return type="+m.getReturnType());
    		    	System.out.println("----");
    		    }
    		}catch(Exception e){
    			e.printStackTrace();
    		}
    	}
    	/**
    	 * 获取构造方法，参数
    	 * */
    	public static void test4(){
    		try{
    			Class cls=Class.forName("com.hch.reflection.mytest");
    			Constructor ctorlist[]=cls.getDeclaredConstructors();
    			for(int i=0;i<ctorlist.length;i++){
    				Constructor ct=ctorlist[i];
    				System.out.println("name:"+ct.getName());
    				System.out.println("decl class:"+ct.getDeclaringClass());
    				Class pvec[]=ct.getParameterTypes();
    				for(int j=0;j<pvec.length;j++){
    					System.out.println("param#"+j+":"+pvec[j]);
    				}
    				Class evec[]=ct.getExceptionTypes();
    				for(int j=0;j<evec.length;j++){
    					System.out.println("exc #"+j+":"+evec[j]);
    				}
    				System.out.println("---------------");
    			}
    		}catch(Exception e){
    			e.printStackTrace();
    		}
    	}
    	/**
    	 * 获取类字段
    	 * */
    	public static void test5(){
    		try{
    			Class cls=Class.forName("com.hch.reflection.mytest");
    			Field fieldlist[]=cls.getDeclaredFields();
    			for(int i=0;i<fieldlist.length;i++){
    				Field fld=fieldlist[i];
    				System.out.println("name="+fld.getName());
    				System.out.println("decl class="+fld.getDeclaringClass());
    				System.out.println("type="+fld.getType());
    				int mod=fld.getModifiers();
    				System.out.println("modifiers："+Modifier.toString(mod));
    				System.out.println("-----------------");
    			}
    		}catch(Exception e){
    			e.printStackTrace();
    		}
    	}
    	/**
    	 * 执行一个方法
    	 * */
    	public static void test6(){
    		try{
    			Class cls=Class.forName("com.hch.reflection.mytest");
    			Class partypes[]=new Class[2];
    			partypes[0]=Integer.TYPE;
    			partypes[1]=Integer.TYPE;
    			
    			Method meth=cls.getMethod("add", partypes);
    			com.hch.reflection.mytest m=new com.hch.reflection.mytest();
    			Object arglist[]=new Object[2];
    			arglist[0]=new Integer(37);
    			arglist[1]=new Integer(42);
    			Object retobj=meth.invoke(m, arglist);
    			Integer retval=(Integer)retobj;
    			System.out.println(retval.intValue());
    		}catch(Exception e){
    			e.printStackTrace();
    		}
    	}
    	/**
    	 * 创建新的对象
    	 * */
    	public static void test7(){
    		try{
    			Class cls=Class.forName("com.hch.reflection.mytest");
    			Class partypes[]=new Class[4];
    			partypes[0]=Integer.TYPE;
    			partypes[1]=String.class;
    			partypes[2]=Boolean.TYPE;
    			partypes[3]=Double.TYPE;
    			Constructor ct=cls.getConstructor(partypes);
    			Object arglist[]=new Object[4];
    			arglist[0]=12;
    			arglist[1]="oooo";
    			arglist[2]=true;
    			arglist[3]=12.3f;
    			com.hch.reflection.mytest retobj=(mytest)ct.newInstance(arglist);
    			System.out.println("obj:"+retobj.a+",c:"+retobj.c);
    			
    		}catch(Exception e){
    			e.printStackTrace();
    		}
    	}
    	/**
    	 * 改变字段
    	 * */
    	public static void test8(){
    		try{
    			Class cls=Class.forName("com.hch.reflection.mytest");
    			Field fld=cls.getField("a");
    			mytest fld2=new com.hch.reflection.mytest();
    			System.out.println("a="+fld2.a);
    			fld.setInt(fld2, 20);
    			System.out.println("a="+fld2.a);
    		}catch(Exception e){
    			e.printStackTrace();
    		}
    	}
    	/**
    	 * 使用数组
    	 * */
    	public static void test9(){
    		try{
    			Class cls=Class.forName("java.lang.String");
    			Object arr=Array.newInstance(cls, 10);
    			Array.set(arr,4,"mytest");
    			Array.set(arr, 5, "This is a test");
    			for(int i=0;i<10;i++){
    				System.out.println("i="+i+",value="+Array.get(arr, i));
    			}
    		}catch(Exception e){
    			e.printStackTrace();
    		}
    	}
    	/**
    	 * 3维数组
    	 * */
    	public static void test10(){
    		try{
    			int dims[]=new int[]{5,10,15};
    			Object arr=Array.newInstance(Integer.TYPE, dims);
    			Object arrobj=Array.get(arr, 3);
    			Class cls=arrobj.getClass().getComponentType();
    			System.out.println(cls);
    			arrobj=Array.get(arrobj, 5);
    			Array.setInt(arrobj, 10, 37);
    			int arrcast[][][]=(int[][][])arr;
    			System.out.println(arrcast[3][5][10]);
    		}catch(Exception e){
    			e.printStackTrace();
    		}
    	}
    	public int add(int a,int b){
    		System.out.println("print:"+(a+b));
    		return a+b;
    	}
    	private int fl(Object p,int x)throws NullPointerException{
    		if(p==null){
    			throw new NullPointerException();
    		}
    		return x;
    	}
    }

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