Java的浅拷贝和深拷贝(1)

 Java的拷贝分为深拷贝和浅拷贝

 

浅拷贝：把一个对象中所有的非static成员变量(包括对其它对象的引用，java中的引用相当于C/C++中的指针变量)都拷贝一遍，而不拷贝引用所指向的对象

深拷贝：把一个对象中所有的非static成员变量(包括对其它对象的引用)都拷贝一遍，引用所指向的对象也拷贝一份

 

这篇文章先讲述浅拷贝，深拷贝下篇文章讲述

 

一个类的对象如果想要具有拷贝的功能，比如符号如下条件：

   1.必须实现Cloneable接口(这个接口中没有定义方法，叫做标记接口)

   2.重写Object类的clone()方法，该方法实现的是浅拷贝

   3.在该类的clone()方法中的第一句，比如调用super.clone()来调用Object的clone()方法来实现拷贝

 

以下是一个浅拷贝的例子：

 

 

package com.test;public class CloneTest{public static void main(String[] args){Student s1 = new Student();s1.setAge(20);s1.setName("wudi");School school = new School();school.setName("Peiyang University");school.setBornYear(1895);s1.setSchool(school);System.out.println("s1:" + s1.getName() + " " + s1.getAge() + " "+ s1.getSchool().getName() + " "+ s1.getSchool().getBornYear());try{//拷贝一个学生Student s2 = (Student)s1.clone();s2.setAge(21);s2.setName("WUDI");System.out.println("s2:" + s2.getName() + " " + s2.getAge() + " "+ s2.getSchool().getName() + " "+ s2.getSchool().getBornYear());System.out.println("after s2 changing some property:");//通过学生s2改变了他所在学校的名称和成立时间s2.getSchool().setName("Tianjin University");s2.getSchool().setBornYear(1951);System.out.println("s1:" + s1.getName() + " " + s1.getAge() + " "+ s1.getSchool().getName() + " "+ s1.getSchool().getBornYear());System.out.println("s2:" + s2.getName() + " " + s2.getAge() + " "+ s2.getSchool().getName() + " "+ s2.getSchool().getBornYear());} catch (CloneNotSupportedException e){e.printStackTrace();}}}class School{private String name;private int bornYear;public String getName(){return name;}public void setName(String name){this.name = name;}public int getBornYear(){return bornYear;}public void setBornYear(int bornYear){this.bornYear = bornYear;}}class Student implements Cloneable{private int age;private String name;private School school;public School getSchool(){return school;}public void setSchool(School school){this.school = school;}public int getAge(){return age;}public void setAge(int age){this.age = age;}public String getName(){return name;}public void setName(String name){this.name = name;}@Overrideprotected Object clone() throws CloneNotSupportedException{return super.clone();}} 

 

 

从运行结果可以看出，通过学生s2将其引用school所指向的对象的name和bornYear属性改变，相应的s1的也被改变，这说明学生s1和学生s2里面的school引用指向的始终是同一个School对象。这就是浅拷贝的含义。