java 引用类型的数据传递的是内存地址
java中引用类型的数据,传递的是内存地址,像类，数组，接口，String等等都是引用类型!
看下面的代码和截图
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public class Test2 { // java中引用类型的数据传递的是内存地址 private Map<String, Student> students = new Hashtable<String, Student>(); public void myTest() { Student student1 = new Student("令狐冲", 16, "华山派", 19888.66); Student student2 = new Student("韦小宝", 15, "紫禁城", 99999.99); Student student3 = new Student("张无忌", 18, "光明顶", 18888.88); students.put("1", student1); students.put("2", student2); students.put("3", student3); Iterator<Map.Entry<String, Student>> entries = students.entrySet().iterator(); while (entries.hasNext()) { Map.Entry<String, Student> entry = entries.next(); System.out.println("Key = " + entry.getKey() + ", Value = " + entry.getValue()); entry.getValue().setAge(entry.getValue().getAge() + 1); } } public void myTest2(){ List<String[]> citys = new ArrayList<String[]>(); String [] cityNames = {"赣州市", "于都县", "江西省", "中国", "赣南地区"}; citys.add(cityNames); for (int index = 0; index < citys.size(); index++) { String[] mycityNames = citys.get(index); for (int i = 0; i < mycityNames.length; i++) { System.out.println(mycityNames[i]); if (i == 1) { //修改mycityNames数组 (java中引用类型的数据传递的是内存地址) mycityNames[i] = "我们" + mycityNames[i]; } } System.out.println("--------------------------------"); for (int i = 0; i < mycityNames.length; i++) { System.out.println(mycityNames[i]); } } System.out.println("--------------------------------"); //修改cityNames数组 (java中引用类型的数据传递的是内存地址) cityNames[0] = "我们赣州市"; for (int index = 0; index < citys.size(); index++) { String[] mycityNames = citys.get(index); for (int i = 0; i < mycityNames.length; i++) { System.out.println(mycityNames[i]); } } } public static void main(String[] args) { Test2 test2 = new Test2(); test2.myTest(); System.out.println("--------------------------------"); Iterator<Map.Entry<String, Student>> entries = test2.students.entrySet().iterator(); while (entries.hasNext()) { Map.Entry<String, Student> entry = entries.next(); System.out.println("Key = " + entry.getKey() + ", Value = " + entry.getValue()); } test2.myTest2(); } } |
list集合存引用数据类型时的问题
集合list的存储元素
（1）如果list中存的是基本数据类型，则存的是值
（2）如果list中存的是引用数据类型（如对象等），则存的是引用
如果对象的引用地址没变，内容变化，也会引起调用该对象时内容变化
下面举一个在集合list中存放对象的例子：
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//构建原始数据 ArrayList<Goods> list = new ArrayList(); Goods goods1=new Goods("plum ", 2); list.add(goods1); list.add(new Goods("apple", 1)); list.add(new Goods("banana", 2)); //打印原始数据 System.out.println("原始数据："); for(Goods goods : list){ System.out.println(goods); } goods1.setGoodsId(444);//改变goods1的内容 System.out.println("原始数据1："); for(Goods goods : list){ System.out.println(goods); } |
结果：
原始数据：
Goods{goodsName='plum ', goodsId=2}
Goods{goodsName='apple', goodsId=1}
Goods{goodsName='banana', goodsId=2}
原始数据1：
Goods{goodsName='plum ', goodsId=444}
Goods{goodsName='apple', goodsId=1}
Goods{goodsName='banana', goodsId=2}
结果表明：由于list中存储对象的引用所指的内容发生了变化，所以导致了list中元素内容的改变
以上为个人经验，希望能给大家一个参考，也希望大家多多支持服务器之家。
原文链接：https://blog.csdn.net/czh500/article/details/79691569
