JAVA反射机制 通过反射 Field类获取和修改对象类的字符串值

ReflecClassPoint01.java

 

package com.sg.reflex;

public class ReflecClassPoint01 {
    private int x;
    public int y ;
   
    public String str1 = "ball";
    public String str2 = "basketball";
    public String str3 = "itcast";
   
    public ReflecClassPoint01() {
        super();
    }

    public ReflecClassPoint01(int x, int y) {
        this.x = x;
        this.y = y;
    }

    @Override
    public String toString() {
        return str1 + ":" + str2 + ":" + str3 ;
    }
   
}

 

 

 

测试ReflecClassPointTest.java

 

 

package com.sg.reflex.test;

import java.lang.reflect.Field;

import com.sg.reflex.ReflecClassPoint01;

public class ReflecClassPointTest {
    public static void main(String[] args) throws Exception{

        ReflecClassPoint01 p = new ReflecClassPoint01(3, 5);
        Field fieldY = p.getClass().getField("y");
        //fieldY 的值是？
        System.out.println(fieldY.get(p));
       
        Field fieldX = p.getClass().getDeclaredField("x");
        //将此对象的 accessible 标志设置为指示的布尔值
        fieldX.setAccessible(true);
        System.out.println(fieldX.get(p));
       
       
        chageStringValue(p);
        System.out.println(p);
    }

    private static void chageStringValue(Object obj) throws Exception{
        Field[] fields = obj.getClass().getFields();
       
        for (Field field : fields) {
            //field.getType();
            //与字节码作比较用==  假如是String的字节码
            if (field.getType() == String.class) {
                String oldValue = (String) field.get(obj);
                //把小写的b换成大写B
                String newValue = oldValue.replace("b","B");
               
                field.set(obj, newValue);
               
            }
        }
    }
   
}