Clonable接口和深拷贝\浅拷贝

拷贝原理

class Person implements Cloneable{
    
    
    public int age = 2;
    @Override
    protected Object clone() throws CloneNotSupportedException {
    
    
        //要想完成克隆,必须调用Object,重写clone()方法
        return super.clone();
    }
    @Override
    public String toString() {
    
    
        return "Person{" +
                "age=" + age +
                '}';
    }
}
public class Test1 {
    
    
    public static void main(String[] args) throws CloneNotSupportedException {
    
    
       Person person1 = new Person();
        Person person2 = (Person)person1.clone();//向下转型
        System.out.println(person1.age);
        System.out.println(person2.age);
    }
    运行结果:
    2
	2

问题:clone方法是Object的方法,所以类都是继承Object的,为什么还要重写克隆方法呢?

我们去看克隆源码发现,克隆是C++代码实现的Object类中的方法.在源代码中Object的访问修饰符是protected修饰的,所以可以得出它们不是在同一包当中.确实可以通过super访问到.但是没有重写克隆方法和传入要克隆的地址.所以代码报错

class Person implements Cloneable{
    
    
    public int age = 2;
//    @Override
//    protected Object clone() throws CloneNotSupportedException {
    
    
//        //要想完成克隆,必须调用Object,重写clone()方法
//        return super.clone();
//    }

    @Override
    public String toString() {
    
    
        return "Person{" +
                "age=" + age +
                '}';
    }
}
public class Test1 {
    
    
    public void func() throws CloneNotSupportedException {
    
    
        Person person1 = new Person();
        Person person2 = (Person)super.clone();
        System.out.println(person1);
        System.out.println(person2);
    }
    public static void main(String[] args) throws CloneNotSupportedException {
    
    
        Test1 test = new Test1();
        test.func();
    }
}

浅拷贝

package com.cou;
class Name implements  Cloneable{
    
    
    public String name = "张三";

    @Override
    protected Object clone() throws CloneNotSupportedException {
    
    
        return super.clone();
    }
}
class Person implements Cloneable{
    
    
    public int age = 2;
    public Name names = new Name();
    @Override
    protected Object clone() throws CloneNotSupportedException {
    
    
        return super.clone();
    }
}
public class Test1 {
    
    
    public static void main(String[] args) throws CloneNotSupportedException {
    
    
        Person person1 = new Person();
        Person person2 = (Person)person1.clone();//向下转型
        System.out.println("person1年龄深拷贝前" + person1.age);
        System.out.println("person2年龄深拷贝前" + person2.age);
        person2.age = 23;
        System.out.println("person1年龄深拷贝后" +person1.age);
        System.out.println("person1年龄深拷贝后" +person2.age);
        System.out.println("名字是深拷贝");
        System.out.println("person1名字浅拷贝前" + person1.names.name);
        System.out.println("person2名字浅拷贝前" + person2.names.name);
        person2.names.name = "王五";
        System.out.println("person1名字浅拷贝后" + person1.names.name);
        System.out.println("person2名字浅拷贝后" + person2.names.name);
    }
}

深拷贝

package com.cou;
class Name implements  Cloneable{
    
    
    public String name = "张三";

    @Override
    protected Object clone() throws CloneNotSupportedException {
    
    
        return super.clone();
    }
}
class Person implements Cloneable{
    
    
    public int age = 2;
    public Name names = new Name();
    @Override
    protected Object clone() throws CloneNotSupportedException {
    
    
        //深拷贝
        Person tmp = (Person) super.clone();
        tmp.names = (Name) this.names.clone();
        return tmp;
    }
}
public class Test1 {
    
    
    public static void main(String[] args) throws CloneNotSupportedException {
    
    
        Person person1 = new Person();
        Person person2 = (Person)person1.clone();//向下转型
        System.out.println("person1年龄深拷贝前" + person1.age);
        System.out.println("person2年龄深拷贝前" + person2.age);
        person2.age = 23;
        System.out.println("person1年龄深拷贝后" +person1.age);
        System.out.println("person1年龄深拷贝后" +person2.age);
        System.out.println("名字是深拷贝");
        System.out.println("person1名字深拷贝前" + person1.names.name);
        System.out.println("person2名字深拷贝前" + person2.names.name);
        person2.names.name = "王五";
        System.out.println("person1名字深拷贝后" + person1.names.name);
        System.out.println("person2名字深拷贝后" + person2.names.name);
    }
}

总结:深拷贝和浅拷贝,不是哪个方法决定的,而是看你自己的代码来决定实现的.