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