java-learning/java-base/src/main/java/com/brianway/learning/java/base/datatype/IntegerChanger.java at master · JavaDevelopRep/java-learning

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package com.brianway.learning.java.base.datatype;

import java.lang.reflect.Field;

/**

* Created by brian on 16/11/1.

* 涉及到的知识点:

* 1.java 的参数传递都是值传递

* 2.Integer的内部实现(value,缓存,等等)

* 3.反射操作(可访问性)

* 4.自动装箱和拆箱

* 参考博客 http://www.voidcn.com/blog/zgwangbo/article/p-6101689.html

public class IntegerChanger {

public static void main(String[] args) {

Integer a = 1, b = 2;

System.out.println("before swap a = " + a + ", b = " + b);

swap(a, b);

System.out.println("after swap a = " + a + ", b = " + b);

Integer c = 1;

System.out.println("(警告:Integer缓存被改了,代码里:Integer c = 1;) 实际c=" + c);

}

public static void swap(Integer i1, Integer i2) {

try {

Field f = Integer.class.getDeclaredField("value");

f.setAccessible(true);

int tmp = i1;

f.setInt(i1, i2);

f.setInt(i2, tmp);

} catch (NoSuchFieldException e) {

e.printStackTrace();

} catch (IllegalAccessException e) {

e.printStackTrace();

}