Java反射-修改String常量

/*
* ReflectString.java
* Version 1.0.0
* Created on 2017年12月15日
* Copyright ReYo.Cn
*/
package reyo.sdk.utils.test.reflect;

import java.lang.reflect.Field;

public class ReflectString {

    public static void main(String[] args) {
        String s1 = "reyo";
        String s2 = "reyo";
        String s3 = new String("reyo");
        String s4 = new String(s1);
        System.out.println("s1==s2:" + (s1 == s2));
        System.out.println("s1==s3:" + (s1 == s3));
        System.out.println("s3==s4:" + (s3 == s4));
        try {
            Field f = String.class.getDeclaredField("value");
            System.out.print("Accessible: " + f.isAccessible());
            f.setAccessible(true);
            System.out.println(" -> " + f.isAccessible());
            char[] v = (char[]) f.get(s1);// 获取S1的内部value数组
            System.out.print("
value:");
            System.out.println(v);
            v[0] = 'x';// 修改数组
            v = new char[1];// 目测因为是get到的是引用的复制，这个引用改变不影响原引用
            v[0] = 'y';
            System.out.print("value:");
            System.out.println(v);

        } catch (Exception e) {
            System.out.println(e.getMessage());
        }
        System.out.println("
s1:" + s1 + "
s2:" + s2 + "
s3:" + s3 + "
s4:" + s4);
        System.out.println("
s1==s2:" + (s1 == s2));
        System.out.println("s1==s3:" + (s1 == s3));
        System.out.println("s3==s4:" + (s3 == s4));
    }
}

s1==s2:true
s1==s3:false
s3==s4:false
Accessible: false -> true

value:reyo
value:y

s1:xeyo
s2:xeyo
s3:xeyo
s4:xeyo

s1==s2:true
s1==s3:false
s3==s4:false