Java中的深复制与浅复制问题

package com.lrq.copy;



public class User implements Cloneable{

public User() {
System.out.println("user");
}

private String username;
private int age;
private Integer length;
public String getUsername() {
return username;
}
public void setUsername(String username) {
this.username &＃61; username;
}
public int getAge() {
return age;
}
public void setAge(int age) {
this.age &＃61; age;
}
public Integer getLength() {
return length;
}
public void setLength(Integer length) {
this.length &＃61; length;
}

private Account account;
public Account getAccount() {
return account;
}
public void setAccount(Account account) {
this.account &＃61; account;
}

//必须要覆盖, 为如果不覆盖的话,父类的protected方法,到了子类就是private的了;对于外部不可用;
&＃64;Override
protected Object clone() throws CloneNotSupportedException {
//copy一个新的东西出来;
User clone &＃61; (User) super.clone();
//将非基本数据类型的数据也copy一份过来;注意必须要copy.
clone.setAccount((Account) this.getAccount().clone());
return clone;
}



}



package com.lrq.copy;



public class Account implements Cloneable{

public Account() {
System.out.println("account");
}
private String id;
private Float money;
public String getId() {
return id;
}
public void setId(String id) {
this.id &＃61; id;
}
public Float getMoney() {
return money;
}
public void setMoney(Float money) {
this.money &＃61; money;
}

&＃64;Override
protected Object clone() throws CloneNotSupportedException {
// TODO Auto-generated method stub
return super.clone();
}

}



这样就实现了源对象和copy对象直接使用互不干扰:
测试代码:

&＃64;Test
public void test() throws Exception{
User user&＃61;new User();
Account account&＃61;new Account();
account.setId("ssss");
account.setMoney(23f);
user.setAccount(account);
user.setAge(20);
user.setLength(111);

User clone &＃61; (User) user.clone();

Account account2 &＃61; clone.getAccount();
System.out.println(account2.getMoney()&＃43;"--clone");


clone.getAccount().setMoney(9999f);
System.out.println(user.getAccount().getMoney());
}
输出结果:user的account还是之前的23;而不是修改后的9999;
这里的核心是不让clone对象获取到源对象中,非基本数据类型的成员变量的引用;
处理方式二:

package com.lrq.copy;



import java.io.ByteArrayInputStream;

import java.io.ByteArrayOutputStream;

import java.io.IOException;

import java.io.ObjectInputStream;

import java.io.ObjectOutputStream;

import java.io.Serializable;



public class Person implements Serializable{



private static final long serialVersionUID &＃61; -8954779984792810004L;



private String id;
private String name;
private Card card;
public String getId() {
return id;
}
public void setId(String id) {
this.id &＃61; id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name &＃61; name;
}
public Card getCard() {
return card;
}
public void setCard(Card card) {
this.card &＃61; card;
}

&＃64;Override
protected Object clone(){
ByteArrayOutputStream bos&＃61;new ByteArrayOutputStream();
try {
ObjectOutputStream objectOut&＃61;new ObjectOutputStream(bos);
objectOut.writeObject(this);

ByteArrayInputStream bis&＃61;new ByteArrayInputStream(bos.toByteArray());
ObjectInputStream objectIn&＃61;new ObjectInputStream(bis);
return objectIn.readObject();
} catch (IOException e) {
e.printStackTrace();
throw new RuntimeException(e);
} catch (ClassNotFoundException e) {
e.printStackTrace();
throw new RuntimeException(e);
}

}

}







package com.lrq.copy;



import java.io.Serializable;



public class Card implements Serializable{

private static final long serialVersionUID &＃61; -6258840793361311762L;
private String id;
private String no;
public String getId() {
return id;
}
public void setId(String id) {
this.id &＃61; id;
}
public String getNo() {
return no;
}
public void setNo(String no) {
this.no &＃61; no;
}


}



测试代 :

&＃64;Test
public void test2(){
Person person&＃61;new Person();
Card card&＃61;new Card();
card.setId("ooo");
card.setNo("xxx");
person.setCard(card);
person.setId("afdaf");
person.setName("dfadffaf");
Person clone &＃61; (Person) person.clone();
clone.getCard().setNo("aaaaaaaaaaaa");
System.out.println(clone.getCard().getNo()&＃43;"clone");

System.out.println(person.getCard().getNo()&＃43;"perosn");
}



完全没问题,建议使用第二种;

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