java-深克隆和浅克隆

文章参考 https://www.cnblogs.com/acode/p/6306887.html

一、前提

    1、使用clone()方法的类，必须实现Cloneable接口，

          否则调用clone()方法时候，会抛出  CloneNotSupportedException

     2、clone()为protected修饰符方法，所以如果想使用clone()方法，必须在子类中实现

二、实战

   类关系（

                Student：两个基础类型属性

                                一个引用类型属性）

    1、创建一个Student类

@Data
public class Student  implements Cloneable{

    private String name;

    private int age;

    private Mother mother ;

    @Override
    protected Object clone() throws CloneNotSupportedException {
        Student student = (Student) super.clone();
        try {
            Mother mother1 = (Mother)mother.clone();
            student.setMother(mother1);
        } catch (Exception e) {
            e.printStackTrace();
        }
        return student;
    }
}

   2、创建一个Mother类

@Data
public class Mother implements Cloneable {

    private String name;

    private int age;
    
    @Override
    protected Object clone() throws CloneNotSupportedException {
        return super.clone();
    }
}

3、创建一个测试类

public class Test {

    public static void main(String[] args) throws  Exception {
        //============初始化================
        Mother mother = new Mother();
        mother.setName("小王mama");
        mother.setAge(40);
        Student student = new Student();
        student.setAge(1);
        student.setName("小王");
        student.setMother(mother);
        //============克隆================
        Student student2 = (Student)student.clone();
        student2.setName("小李");
        student2.setAge(2);
        student2.getMother().setAge(45);
        student2.getMother().setName("小李mama");
        //============输出================
        System.out.println(student);
        System.out.println(student2);
    }
}　　

三、结果

Student(name=小王, age=1, mother=Mother(name=小王mama, age=40))
Student(name=小李, age=2, mother=Mother(name=小李mama, age=45))

四、分析

1、结果实现类深度克隆

2、如果在Student类的clone()方法中没有，进行Mother类的操作，则Mother属性只会进行引用操作

      修改Student类中的clone()方法

@Override
    protected Object clone() throws CloneNotSupportedException {
        return super.clone();
    }

      结果

Student(name=小王, age=1, mother=Mother(name=小李mama, age=45))
Student(name=小李, age=2, mother=Mother(name=小李mama, age=45))

3、歪门邪术（实现序列化接口，实现clone）  对象串行化，但是串行化却很耗时，在一些框架中，我们便可以感受到，它们往往将对象进行串行化后进行传递，耗时较多。

@Data
public class Student  implements Serializable{

    private static final long serialVersionUID = 1L;


    private String name;

    private int age;


    private Mother mother ;

    public Object deepClone() throws IOException, 
            ClassNotFoundException {
        // 将对象写到流里
        ByteArrayOutputStream bo = new ByteArrayOutputStream();
        ObjectOutputStream oo = new ObjectOutputStream(bo);
        oo.writeObject(this);
        // 从流里读出来
        ByteArrayInputStream bi = new ByteArrayInputStream(bo.toByteArray());
        ObjectInputStream oi = new ObjectInputStream(bi);
        return (oi.readObject());
    }
}

@Data
public class Mother implements Serializable {

    private static final long serialVersionUID = 1L;

    private String name;

    private int age;
    
}

结果：深度克隆成功

Student(name=小王, age=1, mother=Mother(name=小王mama, age=40))
Student(name=小李, age=2, mother=Mother(name=小李mama, age=45))