Java反射研究（2）

接Java反射研究（1）

九、调用特定方法

Method m = c1.getMethod("funcname",Class<?>...c);   //funcname表示调用方法的名称，c表示参数的Class对象

例如：Method m = c1.getMethod("fun",String.class,int.class);    表示调用fun（String,int）;函数

Object obj = m.invoke(c1.newInstance(),"xiazdong",20);   //如果有返回值，则invoke函数返回；

注：如果是调用静态的方法，则不需要设置对象；

Object obj = m.invoke(null,"xiazdong");

注：如果参数中有数组，比如 public static void main(String[]args);

则

Method m = c1.getMethod("main",String[].class);

m.invoke(null,(Object)new String[]{"aa","bb"});是对的；

m.invoke(null,new String[]{"aa","bb"}); 会调用 main(String,String);函数；

十、调用特定属性

Field f = c1.getDeclaredField("name");    //返回name属性

f.setAccessible(true);    //私有属性可见

String name = (String)f.get(Object obj);   //返回obj对象的name属性的值

f.set(Object obj,String n);      //设置obj对象的name属性为n值；

十一、操作数组

int tmp[] = {1,2,3};

Class<?> c  = tmp.getClass().getComponentType();

Array.getLength(tmp);        //tmp数组的长度

c.getName();           //获得数组类型名称

Array.get(Object obj,int index);      //获得obj数组的index索引的数值

Array.set(Object obj,int index,VALUE);    //设置obj数组的index索引的数值为value；

Object obj  = Array.newInstance(c,length);          //c为数组的类型，length为数组的长度；obj为返回的数组对象；

示例：

import java.lang.reflect.*;
public class GetMethodDemo01{
	public static void main(String args[])throws Exception{
		Class<?> c1 = Class.forName("Person");
		Method m = c1.getMethod("sayHello");
		m.invoke(c1.newInstance());
		Method m2 = c1.getMethod("sayHello2",String.class,int.class);
		String str = (String)m2.invoke(c1.newInstance(),"xiazdong",123);
		System.out.println(str);
		Field nameField = c1.getDeclaredField("name");
		Field ageField = c1.getDeclaredField("age");
		nameField.setAccessible(true);
		ageField.setAccessible(true);
		Person obj = (Person)c1.newInstance();
		obj.setName("xzdong");
		obj.setAge(12);
		System.out.println(nameField.get(obj));
		System.out.println(ageField.get(obj));
		Method setName = c1.getMethod("setName",String.class);
		setName.invoke(obj,"changed");
		Method getName = c1.getMethod("getName");
		System.out.println(getName.invoke(obj));

		int tmp[] = {1,2,3};
		Class<?> c3 = tmp.getClass().getComponentType();
		System.out.println(c3.getName());
		System.out.println("第一个数："+Array.get(tmp,0));
		Array.set(tmp,0,5);
		System.out.println("第一个数："+Array.get(tmp,0));

		Object arr = Array.newInstance(c3,5);
		System.arraycopy(tmp,0,arr,0,Array.getLength(tmp));
		System.out.println(Array.get(arr,2));
		System.out.println(Array.get(arr,3));
	}
}

import java.lang.reflect.*;
interface China{
	public static final String NAME = "CHINA";
	public int AGE = 60;
	public void sayHello();
	public String sayHello2(String name,int age);
}
class Person implements China{
	private String name;
	private int age;
	public String getName(){
		return name;
	}
	public void setName(String name){
		this.name = name;
	}
	public int getAge(){
		return age;
	}
	public void setAge(int age){
		this.age = age;
	}
	public void sayHello(){
		System.out.println(NAME+"  "+AGE);
	}
	public String sayHello2(String name,int age){
		return name+" "+age;
	}
}