深拷贝和浅拷贝

拷贝对象： 实现cloneable接口，重写clone方法。因为Object里的clone方法是protected的。

 

浅拷贝：

浅拷贝就是拷贝对象里面的对象引用没有被拷贝，还是指向地址。 --下面就是演示 person里面的hobby对象没有被拷贝。还是指向地址

Person类：

@Data
public class Person implements Cloneable{
    private String name;
    private int age;
    private Hobby hobby;

    public Person(String name, int age, Hobby hobby) {
        this.name = name;
        this.age = age;
        this.hobby = hobby;
    }

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

    @Override
    public String toString() {
        return "Person{" +
                "name='" + name + '\'' +
                ", age=" + age +
                ", hobby.like=" + hobby.getLike() + ", hobby.hate=" + hobby.getHate() +
                '}';
    }
}

Hobby类 -- person里的引用，也就是这个不能被拷贝

@Data
public class Hobby implements Cloneable{
    private String like;
    private String hate;
    public Hobby(String like, String hate) {
        this.like = like;
        this.hate = hate;
    }

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

测试类:

public class CloneableTest {
    public static void main(String[] args) throws Exception{
        Person p1 = new Person("shishi", 16, new Hobby("eat", "work"));
        Person p2 = (Person)p1.clone();
        System.out.println(p1);
        System.out.println(p2);
        System.out.println(p1 == p2);
        
        //注意这里修改了p2，但是p1对象也是hard work，说明是浅拷贝。这个hobby对象没有真正被拷贝，而是引用地址。
        p2.getHobby().setHate("hard work");
        System.out.println(p1);
        System.out.println(p2);
    }
}

测试结果：

 

 

深拷贝：

就是重写clone方法的时候，里面的对象引用也要clone

@Data
public class Person implements Cloneable{
    private String name;
    private int age;
    private Hobby hobby;

    public Person(String name, int age, Hobby hobby) {
        this.name = name;
        this.age = age;
        this.hobby = hobby;
    }

    @Override
    protected Object clone() throws CloneNotSupportedException {
        Object o = null;
        o =  super.clone();
        Person p = (Person)o;
        p.hobby = (Hobby)p.getHobby().clone();
        return o;
    }
    @Override
    public String toString() {
        return "Person{" +
                "name='" + name + '\'' +
                ", age=" + age +
                ", hobby.like=" + hobby.getLike() + ", hobby.hate=" + hobby.getHate() +
                '}';
    }
}

再用上面的那段代码测试，就实现了深拷贝：