[2014-11-21]Java笔记_对象的深克隆与浅克隆、clone()

一、深拷贝（deep clone）与浅拷贝（shallow clone）

      浅复制：被复制对象的所有变量都含有与原来的对象相同的值，而所有的对其他对象的引用仍然指向原来的对象。（不复制它所引用的对象）。

      深复制：被复制对象的所有变量都含有与原来的对象相同的值，出去耐心哦引用其他对象的变量。那些引用其他对象的变量将指向被复制过的新对象，而不再是原有的那些被引用的对象。（把要复制的对象所引用的对象都复制了一遍）

package com.bob.clone;

public class CloneTest2
{
public static void main(String[] args) throws Exception
{
Teacher teacher = new Teacher();

teacher.setAge(40);
teacher.setName("Teacher zhang");

Student2 s1 = new Student2();

s1.setAge(20);
s1.setName("zhangsan");
s1.setTeacher(teacher);

Student2 s2 = (Student2)s1.clone();

System.out.println(s2.getName());
System.out.println(s2.getAge());

teacher.setName("Teacher Li");

System.out.println(s2.getTeacher().getName());
System.out.println(s2.getTeacher().getAge());
}
}

class Teacher implements Cloneable
{
private int age;

private 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();	//必须调用父了clone方法获取到对象的类型
}
}

class Student2 implements Cloneable
{
private int age;

private String name;

private 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
{
Student2 student2 = (Student2)super.clone();

//将父类的对象也复制一次
student2.setTeacher((Teacher)student2.getTeacher().clone());	//调用父类的clone方法实现深复制

return student2;
}
}

· 利用序列化来做深复制

    序列化会将对象的所有信息都写入到流中，包或对象中的所有引用信息。可以利用序列化的特点来实现深复制。

package com.bob.clone;

import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.io.Serializable;

public class CloneTest3 {
public static void main(String[] args) throws Exception {
Teacher3 t = new Teacher3();

t.setAge(40);
t.setName("Teacher Zhang");

Student3 s1 = new Student3();

s1.setAge(20);
s1.setName("zhangsan");
s1.setTeacher(t);

Student3 s2 = (Student3) s1.deepCopy();

System.out.println(s2.getAge());
System.out.println(s2.getName());

System.out.println("-----------------------");

System.out.println(s2.getTeacher().getAge());
System.out.println(s2.getTeacher().getName());

s2.getTeacher().setAge(50);
s2.getTeacher().setName("Teacher Li");

System.out.println(s1.getTeacher().getAge());
System.out.println(s1.getTeacher().getName());

}

}

class Teacher3 implements Serializable {
private int age;

private 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 Student3 implements Serializable {
private int age;

private String name;

private Teacher3 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 Teacher3 getTeacher() {
return teacher;
}

public void setTeacher(Teacher3 teacher) {
this.teacher = teacher;
}

public Object deepCopy() throws Exception {
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();
}
}