文章目录

1.定义2.举例 无论是在java面试过程中，还是在与各种老鸟交流的过程中，对java对象的深浅拷贝，都是一个绕不开的问题，这个问题看似很容易，却是大多数人用来区分小白的标准问题。现在对该问题进行说明。

1.定义

浅克隆（拷贝）：复制一个对象的实例，但是这个对象中包含的其它的对象还是共用的。一般用super.clone()方法，clone的对象就是浅克隆。 深克隆（拷贝）：复制一个对象的实例，而且这个对象中包含的其它的对象也要复制一份。如果使用clone()，那么需要对clone方法进行重写，复制一个对象super.clone()，之后再一一对属性进行复制。这样显得非常冗余，幸好，在java中还可以通过流来实现。但是注意，对象需要实现Serializable接口。

2.举例

有如下类Husband, Husband又引用了Wife。

Wife类

package com.dhb.CloneTest; import lombok.Data; import java.io.Serializable; import java.util.Date; @Data public class Wife implements Serializable { private String name; private Date birthday; public Wife() { this.name = "思思"; this.birthday = new Date(); } public Wife(String name, Date birthday) { this.name = name; this.birthday = birthday; } }

Husband类

package com.dhb.CloneTest; import lombok.Data; import java.io.*; import java.util.Date; @Data public class Husband implements Cloneable,Serializable { private Wife wife; private Date birthday; public Husband() { this.wife = new Wife(); this.birthday = new Date(); } public Husband(Wife wife, Date birthday) { this.wife = wife; this.birthday = birthday; } public Object clone() { Husband husband = null; try { husband = (Husband) super.clone(); } catch (CloneNotSupportedException e) { e.printStackTrace(); }finally { return husband; } } public Object deepClone() throws IOException, ClassNotFoundException { ByteArrayOutputStream bos = new ByteArrayOutputStream(); ObjectOutputStream oos = new ObjectOutputStream(bos); oos.writeObject(this); ByteArrayInputStream bis = new ByteArrayInputStream(bos.toByteArray()); ObjectInputStream ois = new ObjectInputStream(bis); return ois.readObject(); } }

在Husband类中存在clone和deepClone方法。现在对这两个方法进行测试。

package com.dhb.CloneTest; import java.io.IOException; public class CloneTest { public static void main(String[] args) { try { Husband husband = new Husband(); System.out.println("husband birthday is :"+husband.getBirthday()); System.out.println("wife birthday is :"+husband.getWife().getBirthday()); System.out.println("***********************************************"); Husband husband1 = (Husband) husband.clone(); System.out.println("husband1 birthday is :"+husband1.getBirthday()); System.out.println("wife birthday is :"+husband1.getWife().getBirthday()); System.out.println("***********************************************"); System.out.println("husband 是否相同："+(husband == husband1)); System.out.println("wife 是否相同："+(husband.getWife() == husband1.getWife())); System.out.println("***********************************************"); Husband husband2 = (Husband) husband.deepClone(); System.out.println("husband2 birthday is :"+husband2.getBirthday()); System.out.println("wife birthday is :"+husband2.getWife().getBirthday()); System.out.println("***********************************************"); System.out.println("husband 是否相同："+(husband == husband2)); System.out.println("wife 是否相同："+(husband.getWife() == husband2.getWife())); } catch (IOException e) { e.printStackTrace(); } catch (ClassNotFoundException e) { e.printStackTrace(); } } }

运行结果：

husband birthday is :Mon Aug 07 19:03:38 CST 2017 wife birthday is :Mon Aug 07 19:03:38 CST 2017 *********************************************** husband1 birthday is :Mon Aug 07 19:03:38 CST 2017 wife birthday is :Mon Aug 07 19:03:38 CST 2017 *********************************************** husband 是否相同：false wife 是否相同：true *********************************************** husband2 birthday is :Mon Aug 07 19:03:38 CST 2017 wife birthday is :Mon Aug 07 19:03:38 CST 2017 *********************************************** husband 是否相同：false wife 是否相同：false

注：上述代码中的@Data 是lombak的一个注解。

当然，实现深克隆的方法并不局限于流这一种办法，还可以通过json等其他办法实现。