Java反射---reflect

最新推荐文章于 2025-12-17 19:02:04 发布

转载最新推荐文章于 2025-12-17 19:02:04 发布 · 129 阅读

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原文链接：http://www.cnblogs.com/Uncho/p/4137574.html

文章标签：

#java

本文深入探讨Java反射机制，包括Class对象获取方式、判断数据类型、访问构造器、方法及字段等核心功能。通过实例演示如何利用反射进行动态类型判断、调用私有成员和创建实例。

Person p = new Person();

1.Class c = String.class;

2.Class c = p.getClass();

3.Class c = Class.forName("java.lang.String");//throw exception

Person p = (Person)c.newInstance();

package com.hoo.reflect;

import java.lang.reflect.Constructor;
import java.lang.reflect.Field;
import java.lang.reflect.Method;

public class TestReflect {
	public static void main(String[] args) throws Exception {
		String str = "abc";
		Class c1 = str.getClass();
		Class c2 = String.class;
		Class c3 = null;
		c3 = Class.forName("java.lang.String");
		System.out.println(c1 == c2);// true
		System.out.println(c1 == c3);// true

		System.out.println(c1.isPrimitive());// false //判断是否基本数据类型
		System.out.println(int.class.isPrimitive());// true
		System.out.println(int.class == Integer.class);// false
		System.out.println(int.class == Integer.TYPE);// true
		System.out.println(int[].class.isPrimitive());// false
		System.out.println(int[].class.isArray());// true
　　　　　　　　　　
		/*
		 * Constructor
		 */
		Constructor<?>[] cs = String.class.getDeclaredConstructors();
		// String.class.getConstructors(); 只能访问public
　　　　　　　　　
		for (Constructor c : cs) {
			c.setAccessible(true);
			System.out.println(c);
		}
		System.out.println(String.class.getConstructor(String.class));

		/*
		 * Method
		 */
		Method[] ms = String.class.getDeclaredMethods();
		for (Method m : ms) {
　　　　　　　　　　　　　　// String s =  Modifier.toString(m.getModifiers()); //public  private default  protected
			m.setAccessible(true);
			System.out.println(m);
		}

		/*
		 * Field
		 */
		Field[] fs = String.class.getDeclaredFields();
		for (Field f : fs) {
			f.setAccessible(true);
			System.out.println(f);
		}

	}
}

package com.hoo.reflect;

import java.lang.reflect.Field;

public class TestReflect2 {
	public static void main(String[] args) throws Exception {
		RefletPoint rp = new RefletPoint(3, 4);
		changeBtoA(rp);
		System.out.println(rp);

	}
	
	private static void changeBtoA(Object obj) throws Exception{
		Field[] fs = obj.getClass().getDeclaredFields();
		for(Field f : fs){
			f.setAccessible(true);
			if(f.getType() == String.class){
				String oldValue = (String)f.get(obj);
				String newValue = oldValue.replace('b', 'a');
				f.set(obj, newValue);
			}
		}
	}

}

class RefletPoint {
	private int x = 0;
	public int y = 0;
	public String str1 = "ball";
	public String str2 = "basketball";
	public String str3 = "itcat";

	public RefletPoint(int x, int y) {
		super();
		this.x = x;
		this.y = y;
	}
	
	@Override
	public String toString() {
		// TODO Auto-generated method stub
		return "ReflectPoint [str1 = " + str1 + " ,str2 = " + str2 + " ,str3 = " + str3 + "]";
	}

}

package com.hoo.reflect;

import java.lang.reflect.Method;

public class TestReflect3 {
	public static void main(String[] args) throws Exception {
		Class c = Class.forName("com.hoo.reflect.S");
		System.out.println(c.isInstance(new Integer(10)));
		System.out.println(c.isInstance(new S()));
		
		
		
		String s = "asdf";
		Method m = String.class.getMethod("charAt", int.class);
		Object ch = m.invoke(s, 3);
		System.out.println(ch);
		
//		System.out.println(m.invoke(s, new Object[]{2}));
	}
}

class S{
}

转载于:https://www.cnblogs.com/Uncho/p/4137574.html