Java對象複製
1.Java對象複製概念
1.1 淺複製（淺克隆）
複製的對象的全部變量與含有與原來的對象相同的值，而全部的對其餘對象的引用仍然指向原對象。換言之，淺複製僅僅複製所考慮的對象，而不復制它所引用的對象。java
1.2 深複製（深度克隆）
複製的對象的全部變量都含有與原來的對象相同的值，除去那些引用其餘對象的變量。那些引用其餘對象的變量將指向複製的新對象，而不是原來的對象。換言之，深複製把要複製的對象所引用的對象都複製了一遍。jvm
2.Java對象的clone()克隆方法
2.1 clone方法
clone方法將對象複製了一份並返回給調用者。通常而言，clone()方法知足ide
- 對任何的對象x，都有x.clone() != x;也即克隆的對象與原對象不是同一個對象，他們有不一樣的內存地址
- 對任何的對象x，都有x.clone().getClass() == x.getClass()，也即克隆對象與原對象的類型一致。
- 若是對象x的equals()方法定義恰當，那麼x.clone().equal(x)應該成立。
2.2 Java中對象的克隆
- 爲了獲取對象的一份拷貝，咱們能夠利用Object的clone()方法
- 在派生類中覆蓋基類的clone()方法，並聲明爲public
- 在派生類的clone()方法中，調用super.clone()。
- 在派生類中實現Cloneable接口
2.3 示例
2.3.1 淺複製示例
package org.wem.im;
/**
*
* <p>
* Title: Person<br>
* Copyright: Copyright (c) 2016<br>
* Company: <br>
* </p>
*
* <p>
* Description: 測試Java對象淺克隆
* </p>
*
* @version v1.0.0
* @author kucs
* @date 2016年9月30日下午2:28:22
*
* Modification History:
*---------------------------------------------------------*
*
*/
public class Person implements Cloneable {
class Worker{
private String workName;
private String department;
public String getWorkName() {
return workName;
}
public void setWorkName(String workName) {
this.workName = workName;
}
public String getDepartment() {
return department;
}
public void setDepartment(String department) {
this.department = department;
}
@Override
public String toString() {
return "Worker [workName=" + workName + ", department=" + department + "]";
}
}
private String name;
private String age;
private String weight;
private String height;
private Worker worker;
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public String getAge() {
return age;
}
public void setAge(String age) {
this.age = age;
}
public String getWeight() {
return weight;
}
public void setWeight(String weight) {
this.weight = weight;
}
public String getHeight() {
return height;
}
public void setHeight(String height) {
this.height = height;
}
public Worker getWorker() {
return worker;
}
public void setWorker(Worker worker) {
this.worker = worker;
}
@Override
protected Object clone() throws CloneNotSupportedException {
// TODO Auto-generated method stub
return super.clone();
}
@Override
public String toString() {
return "Person [name=" + name + ", age=" + age + ", weight=" + weight + ", height=" + height + ", worker="
+ worker + "]";
}
public static void main(String[] args) throws CloneNotSupportedException {
Person p = new Person();
Worker worker = p.new Worker();
worker.setWorkName("asiainfo");
worker.setDepartment("cboss");
p.setWorker(worker);
p.setName("kucs");
p.setAge("24");
p.setWeight("65");
p.setHeight("170");
Person p_clone = (Person) p.clone();
System.out.println("原對象信息："+p.toString());
System.out.println("克隆對象信息："+p_clone.toString());
//修改p_clone對象的值
p_clone.setName("kucs_clone");
//修改對象引用的對象的值
worker.setWorkName("asianinfo_clone");
System.out.println("修改後的克隆對象信息："+p_clone.toString());
System.out.println("原對象信息："+p.toString());
if(p.getWorker().getWorkName().equals(p_clone.getWorker().getWorkName())){
System.out.println("淺複製對象，其引用的對象未複製");
}else{
System.out.println("非淺複製對象，其引用的對象也複製");
}
}
}
運行結果測試
原對象信息：Person [name=kucs, age=24, weight=65, height=170, worker=Worker [workName=asiainfo, department=cboss]] 克隆對象信息：Person [name=kucs, age=24, weight=65, height=170, worker=Worker [workName=asiainfo, department=cboss]] 修改後的克隆對象信息：Person [name=kucs_clone, age=24, weight=65, height=170, worker=Worker [workName=asianinfo_clone, department=cboss]] 原對象信息：Person [name=kucs, age=24, weight=65, height=170, worker=Worker [workName=asianinfo_clone, department=cboss]] 淺複製對象，其引用的對象未複製
結果說明：淺克隆以後的對象與原對象不是同一個對象。修改其中一個對象的值對另外一個對象沒有影響。this
淺克隆中其引用的對象未複製，仍是指向同一個對象。spa
2.3.2 深複製示例
對淺複製示例代碼作了調整code
package org.wem.im;
/**
*
* <p>
* Title: Person<br>
* Copyright: Copyright (c) 2016<br>
* Company: <br>
* </p>
*
* <p>
* Description: 測試Java對象深度克隆
* </p>
*
* @version v1.0.0
* @author kucs
* @date 2016年9月30日下午2:45:22
*
* Modification History:
*---------------------------------------------------------*
*
*/
public class Person implements Cloneable {
class Worker implements Cloneable{
private String workName;
private String department;
public String getWorkName() {
return workName;
}
public void setWorkName(String workName) {
this.workName = workName;
}
public String getDepartment() {
return department;
}
public void setDepartment(String department) {
this.department = department;
}
@Override
protected Object clone() throws CloneNotSupportedException {
// TODO Auto-generated method stub
return super.clone();
}
@Override
public String toString() {
return "Worker [workName=" + workName + ", department=" + department + "]";
}
}
private String name;
private String age;
private String weight;
private String height;
private Worker worker;
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public String getAge() {
return age;
}
public void setAge(String age) {
this.age = age;
}
public String getWeight() {
return weight;
}
public void setWeight(String weight) {
this.weight = weight;
}
public String getHeight() {
return height;
}
public void setHeight(String height) {
this.height = height;
}
public Worker getWorker() {
return worker;
}
public void setWorker(Worker worker) {
this.worker = worker;
}
@Override
protected Object clone() throws CloneNotSupportedException {
// TODO Auto-generated method stub
Person p = (Person) super.clone();
p.worker = (Worker) worker.clone();
return p;
}
@Override
public String toString() {
return "Person [name=" + name + ", age=" + age + ", weight=" + weight + ", height=" + height + ", worker="
+ worker + "]";
}
public static void main(String[] args) throws CloneNotSupportedException {
Person p = new Person();
Worker worker = p.new Worker();
worker.setWorkName("asiainfo");
worker.setDepartment("cboss");
p.setWorker(worker);
p.setName("kucs");
p.setAge("24");
p.setWeight("65");
p.setHeight("170");
Person p_clone = (Person) p.clone();
System.out.println("原對象信息："+p.toString());
System.out.println("克隆對象信息："+p_clone.toString());
//修改p_clone對象的值
p_clone.setName("kucs_clone");
//修改對象引用的對象的值
worker.setWorkName("asianinfo_clone");
System.out.println("修改後的克隆對象信息："+p_clone.toString());
System.out.println("原對象信息："+p.toString());
if(p.getWorker().getWorkName().equals(p_clone.getWorker().getWorkName())){
System.out.println("淺複製對象，其引用的對象未複製");
}else{
System.out.println("非淺複製對象，其引用的對象也複製");
}
}
}
運行結果：對象
原對象信息：Person [name=kucs, age=24, weight=65, height=170, worker=Worker [workName=asiainfo, department=cboss]] 克隆對象信息：Person [name=kucs, age=24, weight=65, height=170, worker=Worker [workName=asiainfo, department=cboss]] 修改後的克隆對象信息：Person [name=kucs_clone, age=24, weight=65, height=170, worker=Worker [workName=asiainfo, department=cboss]] 原對象信息：Person [name=kucs, age=24, weight=65, height=170, worker=Worker [workName=asianinfo_clone, department=cboss]] 非淺複製對象，其引用的對象也複製
結果說明：深克隆中，對克隆後的對象修改值，不影響原對象的值。修改克隆後的對象引用的值，對原對象引用的對象也沒有影響。接口
3.利用串行化來作深複製ip
這主要是爲了不重寫比較複雜的深複製clone()方法。把對象寫到流裏的過程是串行化過程（Serialization），把對象從流中讀取出來是並行化（Deserialization）過程。
注意：寫在流裏的對象時一個拷貝，而原對象仍然存在jvm中，所以串行化過程只是一個對象的拷貝。
在Java語言中，深複製一個對象，經常能夠先使用對象實現Serializable接口，而後把對象寫到一個流裏，再從流裏讀取出來，即可以重建對象。
package org.wem.im;
import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.io.Serializable;
/**
*
* <p>
* Title: Person<br>
* Copyright: Copyright (c) 2016<br>
* Company: <br>
* </p>
*
* <p>
* Description: 測試Java對象克隆
* </p>
*
* @version v1.0.0
* @author kucs
* @date 2016年9月30日下午2:28:22
*
* Modification History:
*---------------------------------------------------------*
*
*/
public class Person implements Serializable {
class Worker implements Serializable{
private String workName;
private String department;
public String getWorkName() {
return workName;
}
public void setWorkName(String workName) {
this.workName = workName;
}
public String getDepartment() {
return department;
}
public void setDepartment(String department) {
this.department = department;
}
@Override
public String toString() {
return "Worker [workName=" + workName + ", department=" + department + "]";
}
}
private String name;
private String age;
private String weight;
private String height;
private Worker worker;
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public String getAge() {
return age;
}
public void setAge(String age) {
this.age = age;
}
public String getWeight() {
return weight;
}
public void setWeight(String weight) {
this.weight = weight;
}
public String getHeight() {
return height;
}
public void setHeight(String height) {
this.height = height;
}
public Worker getWorker() {
return worker;
}
public void setWorker(Worker worker) {
this.worker = worker;
}
public Object deepClone() throws IOException, ClassNotFoundException{
//將對象寫到流
ByteArrayOutputStream bo = new ByteArrayOutputStream();
ObjectOutputStream oo = new ObjectOutputStream(bo);
oo.writeObject(this);
//從流裏讀取處理啊
ByteArrayInputStream bi = new ByteArrayInputStream(bo.toByteArray());
ObjectInputStream oi = new ObjectInputStream(bi);
return oi.readObject();
}
@Override
public String toString() {
return "Person [name=" + name + ", age=" + age + ", weight=" + weight + ", height=" + height + ", worker="
+ worker + "]";
}
public static void main(String[] args) throws CloneNotSupportedException, ClassNotFoundException, IOException {
Person p = new Person();
Worker worker = p.new Worker();
worker.setWorkName("asiainfo");
worker.setDepartment("cboss");
p.setWorker(worker);
p.setName("kucs");
p.setAge("24");
p.setWeight("65");
p.setHeight("170");
Person p_clone = (Person) p.deepClone();
System.out.println("原對象信息："+p.toString());
System.out.println("克隆對象信息："+p_clone.toString());
//修改p_clone對象的值
p_clone.setName("kucs_clone");
//修改對象引用的對象的值
worker.setWorkName("asianinfo_clone");
System.out.println("修改後的克隆對象信息："+p_clone.toString());
System.out.println("原對象信息："+p.toString());
if(p.getWorker().getWorkName().equals(p_clone.getWorker().getWorkName())){
System.out.println("淺複製對象，其引用的對象未複製");
}else{
System.out.println("非淺複製對象，其引用的對象也複製");
}
}
}
運行結果
原對象信息：Person [name=kucs, age=24, weight=65, height=170, worker=Worker [workName=asiainfo, department=cboss]] 克隆對象信息：Person [name=kucs, age=24, weight=65, height=170, worker=Worker [workName=asiainfo, department=cboss]] 修改後的克隆對象信息：Person [name=kucs_clone, age=24, weight=65, height=170, worker=Worker [workName=asiainfo, department=cboss]] 原對象信息：Person [name=kucs, age=24, weight=65, height=170, worker=Worker [workName=asianinfo_clone, department=cboss]] 非淺複製對象，其引用的對象也複製
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