Clonable接口和深拷贝\浅拷贝

川长思鸟来 2023-10-04 18:45 41阅读 0赞

### 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

![在这里插入图片描述][02a48db8b240427aa8343da24ddb02d3.png_pic_center]

**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?**

![在这里插入图片描述][33025e8cb98044b7b7b1b9d60ea87cd6.png_pic_center]

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();
        }
    }

![在这里插入图片描述][6b07dca3d5624c1b8a68933fcf934ab1.png_pic_center]

#### 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);
        }
    }

![在这里插入图片描述][f7b1a67470474690a510cc0ebbe05239.png_pic_center]

![在这里插入图片描述][23969d55688f4859833abeaa4ecd7fbb.png_pic_center]

#### 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);
        }
    }

![在这里插入图片描述][6f33f40aba944e609c689d3bff79d1e8.png_pic_center]

**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.**

[02a48db8b240427aa8343da24ddb02d3.png_pic_center]: https://img-blog.csdnimg.cn/02a48db8b240427aa8343da24ddb02d3.png#pic_center
[33025e8cb98044b7b7b1b9d60ea87cd6.png_pic_center]: https://img-blog.csdnimg.cn/33025e8cb98044b7b7b1b9d60ea87cd6.png#pic_center
[6b07dca3d5624c1b8a68933fcf934ab1.png_pic_center]: https://img-blog.csdnimg.cn/6b07dca3d5624c1b8a68933fcf934ab1.png#pic_center
[f7b1a67470474690a510cc0ebbe05239.png_pic_center]: https://img-blog.csdnimg.cn/f7b1a67470474690a510cc0ebbe05239.png#pic_center
[23969d55688f4859833abeaa4ecd7fbb.png_pic_center]: https://img-blog.csdnimg.cn/23969d55688f4859833abeaa4ecd7fbb.png#pic_center
[6f33f40aba944e609c689d3bff79d1e8.png_pic_center]: https://img-blog.csdnimg.cn/6f33f40aba944e609c689d3bff79d1e8.png#pic_center