java中的浅拷贝与深拷贝

浅拷贝：

package test;

class Student implements Cloneable {
private int number;

public int getNumber() {
return number;
}

public void setNumber(int number) {
this.number = number;
}

@Override
public Object clone() {
Student stu = null;
try {
stu = (Student) super.clone();
} catch (CloneNotSupportedException e) {
e.printStackTrace();
}
return stu;
}
}

public class Test {

public static void main(String args[]) {

Student stu1 = new Student();
stu1.setNumber(12345);
Student stu2 = (Student) stu1.clone();

System.out.println("学生1:" + stu1.getNumber());
System.out.println("学生2:" + stu2.getNumber());

stu2.setNumber(54321);

System.out.println("学生1:" + stu1.getNumber());
System.out.println("学生2:" + stu2.getNumber());
}
}

深拷贝：

package test2;

class Address implements Cloneable{
private String add;

public String getAdd() {
return add;
}

public void setAdd(String add) {
this.add = add;
}

@Override
public Object clone() {
Address stu = null;
try {
stu = (Address) super.clone();
} catch (CloneNotSupportedException e) {
e.printStackTrace();
}
return stu;
}
}

class Student implements Cloneable {
private int number;

private Address addr;

public Address getAddr() {
return addr;
}

public void setAddr(Address addr) {
this.addr = addr;
}

public int getNumber() {
return number;
}

public void setNumber(int number) {
this.number = number;
}

@Override
public Object clone() {
Student stu = null;
try {
stu = (Student) super.clone();
} catch (CloneNotSupportedException e) {
e.printStackTrace();
}
stu.addr = (Address) addr.clone();
return stu;
}
}

public class test {

public static void main(String args[]) {

Address addr = new Address();
addr.setAdd("杭州市");
Student stu1 = new Student();
stu1.setNumber(123);
stu1.setAddr(addr);

Student stu2 = (Student) stu1.clone();

System.out.println("学生1:" + stu1.getNumber() + ",地址:" + stu1.getAddr().getAdd());
System.out.println("学生2:" + stu2.getNumber() + ",地址:" + stu2.getAddr().getAdd());

addr.setAdd("西湖区");
System.out.println("学生1:" + stu1.getNumber() + ",地址:" + stu1.getAddr().getAdd());
System.out.println("学生2:" + stu2.getNumber() + ",地址:" + stu2.getAddr().getAdd());
}
}

利用序列化来做深复制,把对象写到流里的过程是序列化（Serilization）过程，而把对象从流中读出来的过程则叫做反序列化（Deserialization）过程。应当指出的是，写在流里的是对象的一个拷贝，而原对象仍然存在于JVM里面。，利用这个特性，可以做深拷贝 。

import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.io.Serializable;
//利用序列化来做深复制
//深clone

public class DeepCloneTest
{

public static void main(String[] args) throws Exception
{
// teacher对象将不被clone出来的Student对象共享.
Teacher teacher = new Teacher();
teacher.setAge(40);
teacher.setName("Teacher zhang");

Student student1 = new Student();
student1.setAge(20);
student1.setName("zhangsan");
student1.setTeacher(teacher);

// 复制出来一个对象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的引用对象
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
// 如果你的对象序列化后存到硬盘上面后，可是后来你却更改了类的field(增加或减少或改名)，当你反序列化时，就会出现Exception的，这样就会造成不兼容性的问题。
// 但当serialVersionUID相同时，它就会将不一样的field以type的缺省值赋值(如int型的是0,String型的是null等)，这个可以避开不兼容性的问题。所以最好给serialVersionUID赋值
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
{
// 将该对象序列化成流,因为写在流里的是对象的一个拷贝，而原对象仍然存在于JVM里面。所以利用这个特性可以实现对象的深拷贝
ByteArrayOutputStream bos = new ByteArrayOutputStream();

ObjectOutputStream oos = new ObjectOutputStream(bos);

oos.writeObject(this);

// 将流序列化成对象
ByteArrayInputStream bis = new ByteArrayInputStream(bos.toByteArray());

ObjectInputStream ois = new ObjectInputStream(bis);

return ois.readObject();
}
}

输出结果为：
20
zhangsan
~~~~~~~~~~~~~~~~~~~~~~
40
Teacher zhang
~~~~~~~~~~~~~~~~~~~~~~
40
Teacher zhang