693
外匯
java 淺複製和深複製
原文：https://ttitfly.iteye.com/blog/155422
1.java裏的clone分為：
A:淺複製（淺克隆）: 淺複製僅僅複製所考慮的對象，而不複製它所引用的對象。
b:深複製（深克隆）：深複製把要複製的對象所引用的對象都複製了一遍。
Java中對象的克隆,為了獲取對象的一份拷貝，我們可以利用Object類的clone()方法。必須要遵循下麵三點
1.在派生類中覆蓋基類的clone()方法，並聲明為public【Object類中的clone()方法為protected的】。
2.在派生類的clone()方法中，調用super.clone()。
3.在派生類中實現Cloneable接口。
Object類裏的clone方法是淺複製（淺克隆）
淺複製（淺克隆）的例子如下：
package com.test;
//淺複製（淺克隆）: 淺複製僅僅複製所考慮的對象，而不複製它所引用的對象。
//深複製（深克隆）：深複製把要複製的對象所引用的對象都複製了一遍。
//
//Java中對象的克隆,為了獲取對象的一份拷貝，我們可以利用Object類的clone()方法。必須要遵循下麵三點
//1.在派生類中覆蓋基類的clone()方法，並聲明為public【Object類中的clone()方法為protected的】。
//2.在派生類的clone()方法中，調用super.clone()。
//3.在派生類中實現Cloneable接口。
//[color=red]Object類裏的clone方法是淺複製（淺克隆）[/color]public class CloneTest {
public static void main(String[] args) throws Exception{
//teacher對象將被clone出來的Student對象共享.
Teacher teacher = new Teacher();
teacher.setAge(40);
teacher.setName("Teacher zhang");
Student student1 = new Student();
student1.setAge(20);
student1.setName("zhangsan");
student1.setTeacher(teacher);
//複製出來一個對象student2
Student student2 = (Student)student1.clone();
System.out.println(student2.getAge());
System.out.println(student2.getName());
System.out.println("~~~~~~~~~~~~~~~~~~~~~~");
System.out.println(student1.getTeacher().getAge());
System.out.println(student1.getTeacher().getName());
//修改student2的引用對象
student2.getTeacher().setAge(50);
student2.getTeacher().setName("Teacher Li");
System.out.println("~~~~~~~~~~~~~~~~~~~~~~");
System.out.println(student1.getTeacher().getAge());
System.out.println(student1.getTeacher().getName());
}
}
class Teacher {
public int age;
public String name;
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;
}
}
class Student implements Cloneable{
public int age ;
public String name;
public Teacher teacher;
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;
}
public Teacher getTeacher() {
return teacher;
}
public void setTeacher(Teacher teacher) {
this.teacher = teacher;
}
@Override
public Object clone() throws CloneNotSupportedException {
return super.clone();
}
}
輸出結果為：
20
zhangsan
~~~~~~~~~~~~~~~~~~~~~~
40
Teacher zhang
~~~~~~~~~~~~~~~~~~~~~~
50
Teacher Li
2.深複製（深Clone）例子：
package com.test1;
//深clone
public class DeepCloneTest {
public static void main(String[] args) throws Exception{
//teacher對象將不被clone出來的Student對象共享.
Teacher teacher = new Teacher();
teacher.setAge(40);
teacher.setName("Teacher zhang");
Student student1 = new Student();
student1.setAge(20);
student1.setName("zhangsan");
student1.setTeacher(teacher);
//複製出來一個對象student2
Student student2 = (Student)student1.clone();
System.out.println(student2.getAge());
System.out.println(student2.getName());
System.out.println("~~~~~~~~~~~~~~~~~~~~~~");
System.out.println(student1.getTeacher().getAge());
System.out.println(student1.getTeacher().getName());
//修改student2的引用對象
student2.getTeacher().setAge(50);
student2.getTeacher().setName("Teacher Li");
System.out.println("~~~~~~~~~~~~~~~~~~~~~~");
System.out.println(student1.getTeacher().getAge());
System.out.println(student1.getTeacher().getName());
}
}
class Teacher implements Cloneable{
public int age;
public String name;
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;
}
@Override
public Object clone() throws CloneNotSupportedException {
return super.clone();
}
}
class Student implements Cloneable{
public int age ;
public String name;
public Teacher teacher;
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;
}
public Teacher getTeacher() {
return teacher;
}
public void setTeacher(Teacher teacher) {
this.teacher = teacher;
}
@Override
public Object clone() throws CloneNotSupportedException {
Student student = (Student)super.clone();
//將引用的對象teacher也clone下
student.setTeacher((Teacher)(student.getTeacher().clone()));
return student;
}
}
輸出結果為：
20
zhangsan
~~~~~~~~~~~~~~~~~~~~~~
40
Teacher zhang
~~~~~~~~~~~~~~~~~~~~~~
40
Teacher zhang
3.利用序列化來做深複製,把對象寫到流裏的過程是序列化（Serilization）過程，而把對象從流中讀出來的過程則叫做反序列化（Deserialization）過程。應當指出的是，寫在流裏的是對象的一個拷貝，而原對象仍然存在於JVM裏麵。，利用這個特性，可以做深拷貝
package com.test3;
import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.io.Serializable;
//利用序列化來做深複製
//深clone
public class DeepCloneTest {
public static void main(String[] args) throws Exception{
//teacher對象將不被clone出來的Student對象共享.
Teacher teacher = new Teacher();
teacher.setAge(40);
teacher.setName("Teacher zhang");
Student student1 = new Student();
student1.setAge(20);
student1.setName("zhangsan");
student1.setTeacher(teacher);
//複製出來一個對象student2
Student student2 = (Student)student1.deepCopy();
System.out.println(student2.getAge());
System.out.println(student2.getName());
System.out.println("~~~~~~~~~~~~~~~~~~~~~~");
System.out.println(student1.getTeacher().getAge());
System.out.println(student1.getTeacher().getName());
//修改student2的引用對象
student2.getTeacher().setAge(50);
student2.getTeacher().setName("Teacher Li");
System.out.println("~~~~~~~~~~~~~~~~~~~~~~");
System.out.println(student1.getTeacher().getAge());
System.out.println(student1.getTeacher().getName());
}
}
class Teacher implements Serializable{
private static final long serialVersionUID = -8834559347461591191L;
public int age;
public String name;
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;
}
}
class Student implements Serializable{
//serialVersionUID 如果你的對象序列化後存到硬盤上麵後，可是後來你卻更改了類的field(增加或減少或改名)，當你反序列化時，就會出現Exception的，這樣就會造成不兼容性的問題。
//但當serialVersionUID相同時，它就會將不一樣的field以type的缺省值賦值(如int型的是0,String型的是null等)，這個可以避開不兼容性的問題。所以最好給serialVersionUID賦值
private static final long serialVersionUID = 7991552226614088458L;
public int age ;
public String name;
public Teacher teacher;
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;
}
public Teacher getTeacher() {
return teacher;
}
public void setTeacher(Teacher teacher) {
this.teacher = teacher;
}
public Object deepCopy() throws Exception{
//將該對象序列化成流,因為寫在流裏的是對象的一個拷貝，而原對象仍然存在於JVM裏麵。所以利用這個特性可以實現對象的深拷貝
ByteArrayOutputStream bos = new ByteArrayOutputStream();
ObjectOutputStream oos = new ObjectOutputStream(bos);
oos.writeObject(this);
//將流序列化成對象
ByteArrayInputStream bis = new ByteArrayInputStream(bos.toByteArray());
ObjectInputStream ois = new ObjectInputStream(bis);
return ois.readObject();
}
}
輸出結果為：
20
zhangsan
~~~~~~~~~~~~~~~~~~~~~~
40
Teacher zhang
~~~~~~~~~~~~~~~~~~~~~~
40
Teacher zhang
最後更新：2017-04-02 06:52:12