java clone
简介
实现Cloneable接口的类才可以被克隆,如果不实现该接口,调用Object clone方法会报CloneNotSupportedException:
InvokingObject's clone method on an instance that does not implement theCloneableinterface results in the exceptionCloneNotSupportedExceptionbeing thrown.
分类
- 浅克隆 指拷贝对象时仅拷贝对象本身中的基本变量,而不拷贝对象包含的引用指向的对象
- 深克隆 不仅拷贝对象本身中的基本变量，而且还拷贝对象中包含的引用指向的所有对象
说明
package com.lios.clone;
/**
* @author LiosWong
* @description
* @date 2018/6/25 上午4:11
*/
public class Person implements Cloneable {
private String name;
private Worker worker;
public Person(String name, Worker worker) {
this.name = name;
this.worker = worker;
}
public String getName() {
return name;
}
public Person setName(String name) {
this.name = name;
return this;
}
@Override
protected Object clone() throws CloneNotSupportedException {
return super.clone();
}
public static void main(String[] args) {
Person p = new Person("lios", new Worker("worker", 25));
Person p1 = p;
System.out.println("p:toString:" + p + ",hashCode:" + p.hashCode() + ",Worker:" + p.getWorker().hashCode() + ",name=" + p.getName().hashCode());
System.out.println("p1:toString:" + p1 + ",hashCode:" + p1.hashCode() + ",Worker:" + p1.getWorker().hashCode() + ",name=" + p1.getName().hashCode());
System.out.println(p1);
System.out.println("=====================");
try {
Person p2 = (Person) p.clone();
System.out.println("p:Worker:name:"+p.getWorker().getName());
System.out.println("p1:Worker:name:"+p1.getWorker().getName());
System.out.println("p2:Worker:name:"+p2.getWorker().getName());
System.out.println("p2:toString:" + p2 + ",hashCode:" + p2.hashCode() + ",Worker:" + p2.getWorker().hashCode() + ",name=" + p2.getName().hashCode());
p.getWorker().setName("workp");
p.setName("cc");
System.out.println("p2:toString:" + p2 + ",hashCode:" + p2.hashCode() + ",Worker:" + p2.getWorker().hashCode() + ",name=" + p2.getName().hashCode());
System.out.println("p:Worker:name:"+p.getWorker().getName());
System.out.println("p1:Worker:name:"+p1.getWorker().getName());
System.out.println("p2:Worker:name:"+p2.getWorker().getName());
System.out.println("p:"+p.getName());
System.out.println("p1:"+p1.getName());
System.out.println("p2:"+p2.getName());
} catch (CloneNotSupportedException e) {
e.printStackTrace();
}
}
public Worker getWorker() {
return worker;
}
public Person setWorker(Worker worker) {
this.worker = worker;
return this;
}
public static class Worker implements Cloneable {
private String name;
private Integer age;
public Worker(String name, Integer age) {
this.name = name;
this.age = age;
}
@Override
protected Object clone() throws CloneNotSupportedException {
return super.clone();
}
public String getName() {
return name;
}
public Worker setName(String name) {
this.name = name;
return this;
}
public Integer getAge() {
return age;
}
public Worker setAge(Integer age) {
this.age = age;
return this;
}
}
}执行结果为:
p:toString:com.lios.clone.Person@2401f4c3,hashCode:604107971,Worker:123961122,name=3321889
p1:toString:com.lios.clone.Person@2401f4c3,hashCode:604107971,Worker:123961122,name=3321889
com.lios.clone.Person@2401f4c3
=====================
p:Worker:name:worker
p1:Worker:name:worker
p2:Worker:name:worker
p2:toString:com.lios.clone.Person@4926097b,hashCode:1227229563,Worker:123961122,name=3321889
p2:toString:com.lios.clone.Person@4926097b,hashCode:1227229563,Worker:123961122,name=3321889
p:Worker:name:workp
p1:Worker:name:workp
p2:Worker:name:workp
p:cc
p1:cc
p2:lios发现p,p1所有的值都是一致的,当对象p中重置name属性的值、Worker属性中name的值后,p、p1、p2中属性Worker中name属性值都改变了且值相同,但是p2中的name属性值没有变化,下面用图描述:
p1与p指向堆中的同一块内存区域,p2虽然与p、p1不是指向同一块内存区域,但是它们中的Worker属性都引用同一块内存区域,其实这就是浅克隆,修改上面clone方法:
@Override
protected Object clone() throws CloneNotSupportedException {
Person p = (Person) super.clone();
p.worker = (Worker) p.getWorker().clone();
return p;
}再执行,结果如下:
p:toString:com.lios.clone.Person@2401f4c3,hashCode:604107971,Worker:123961122,name=3321889
p1:toString:com.lios.clone.Person@2401f4c3,hashCode:604107971,Worker:123961122,name=3321889
com.lios.clone.Person@2401f4c3
=====================
p:Worker:name:worker
p1:Worker:name:worker
p2:Worker:name:worker
p2:toString:com.lios.clone.Person@4926097b,hashCode:1227229563,Worker:1982791261,name=3321889
p2:toString:com.lios.clone.Person@4926097b,hashCode:1227229563,Worker:1982791261,name=3321889
p:Worker:name:workp
p1:Worker:name:workp
p2:Worker:name:worker
p:cc
p1:cc
p2:lios发现此时p2中属性Worker中的name属性值没有改变,仅仅p、p1中属性Worker中的name属性值改变了,图示:
上面就是深克隆
总结
- 对象被clone必须实现Cloneable接口
- 深克隆需拷贝对象中包含的引用指向的所有对象
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原始发表：2018-07-01，如有侵权请联系 cloudcommunity@tencent.com 删除
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