深克隆浅拷贝

一：直接赋值

public class Dog implements Serializable{
    /**
     * 
     */
    private static final long serialVersionUID = 1L;
    private String name;

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    @Override
    public String toString() {
        return "Dog [name=" + name + "]";
    }
    
}
public class Test1 {
    public static void main(String[] args) {
        Dog dog0 = new Dog();
        dog0.setName("小黑");
        //直接赋值
        Dog dog1 = dog0;
        //查看结果
        System.out.println(dog0.toString());
        System.out.println(dog1.toString());
        
        //改变dog0的name值
        dog0.setName("小白");
        //查看结果
        System.out.println(dog0.toString());
        System.out.println(dog1.toString());
    }
}

改变其中任意一个对象，另一个也会跟着改变

二：浅拷贝（注意里面有个dog对象）
实现Cloneable接口，并重载clone方法

public class CopyObj implements Cloneable{
    private String name;
    private Dog dog;
    public Object clone(){
        try {
            return super.clone();
        } catch (CloneNotSupportedException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
            return null;
        }
    }
    @Override
    public String toString() {
        return "CopyObj [dog=" + dog + ", name=" + name + "]";
    }
    public Dog getDog() {
        return dog;
    }
    public void setDog(Dog dog) {
        this.dog = dog;
    }
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
}
public class Test2 {
    public static void main(String[] args) {
        //设置初始属性值
        Dog dog = new Dog();
        dog.setName("小黑");
        CopyObj a = new CopyObj();
        a.setDog(dog);
        a.setName("小明");
        //调用clone方法
        CopyObj b = (CopyObj) a.clone();
        //查看a和b的属性值
        System.out.println("a:"+a.toString());
        System.out.println("b:"+b.toString());
        //改变a中的基本数据类型的属性值
        a.setName("小强");
        //再查看a和b的属性值，你会发现a的改变了，而b的没有改变
        System.out.println("a:"+a.toString());
        System.out.println("b:"+b.toString());
        //继续...修改dog的name
        dog.setName("小白");
        //再来查看属性值
        System.out.println("a:"+a.toString());
        System.out.println("b:"+b.toString());
        //a和b里面的dog的name一起改变了，这就是浅拷贝的不足之处：
        //如果对象里面的属性值都是基本数据类型，这两个对象任意一个改变都不会影响对方的
        //但是如果对象里面某个属性是引用类型，那么就会复制这个属性（dog）的引用，
        //在改变属性（dog）里面的属性时，相应的对象（a和b）里面的dog也会跟着改变
    }
}

结果：

三：深克隆
实现Serializable接口

public class CloneObj implements Serializable{

    private static final long serialVersionUID = 1L;
    private String name;
    private Dog dog;
    
    @Override
    public String toString() {
        return "CloneObj [dog=" + dog + ", name=" + name + "]";
    }
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public Dog getDog() {
        return dog;
    }
    public void setDog(Dog dog) {
        this.dog = dog;
    }
}
public class CloneUtil {
    /**
     * 深克隆
     * @param <T>
     * @param obj
     * @return
     * @throws IOException
     * @throws ClassNotFoundException 
     */
    @SuppressWarnings("unchecked")
    public static <T extends Serializable>T clone(T obj) 
                  throws IOException, ClassNotFoundException{
        //将对象写入到流里面
        ByteArrayOutputStream baos = new ByteArrayOutputStream();
        ObjectOutputStream oos = new ObjectOutputStream(baos);
        oos.writeObject(obj);
        //从流里面读取对象
        ByteArrayInputStream bais = new ByteArrayInputStream(baos.toByteArray());
        ObjectInputStream ois = new ObjectInputStream(bais);
        return (T) ois.readObject();
    }
}
public class Test3 {
    public static void main(String[] args) 
                throws IOException, ClassNotFoundException {
        //设置初始值
        Dog dog = new Dog();
        dog.setName("小黑");
        CloneObj a = new CloneObj();
        a.setDog(dog);
        a.setName("小明");
        //通过序列化反序列化深克隆
        CloneObj b = CloneUtil.clone(a);
        //查看属性值
        System.out.println("a:"+a.toString());
        System.out.println("b:"+b.toString()+"\n");
        //修改dog的name
        dog.setName("小白");
        System.out.println("a:"+a.toString());
        System.out.println("b:"+b.toString()+"\n");
        //最后a里面的dog的name改变了
        //而b里面的dog的name没有改变
        //这就是深克隆
    }
}

结果：