淺克隆

只復制了基本數(shù)據(jù)類型和String數(shù)據(jù)類型以及對應的數(shù)組類型，其他引用數(shù)據(jù)類型只是復制了引用地址；

使用方式

實現(xiàn)Cloneable接口，然后重寫clone方法，調(diào)用super.clone()即可

public static class Person implements Cloneable {
    @Override
    protected Person clone() throws CloneNotSupportedException {
         return (Person) super.clone();
    }
}

例如

public static class Person implements Cloneable {
    public String name;
    public int age;
    public String[] names;
    public Baby baby;
    public ArrayList<String> names2 = new ArrayList<>();
    public Person(String name, int age) {
        this.name = name;
        this.age = age;
    }
    @Override
    public String toString() {
        return "Person{" + "name='" + name + '\'' + ", age=" + age + ", names=" + Arrays.toString(names) + ", baby=" + baby + ", names2=" + names2 + '}';
    }
    @Override
    protected Person clone() throws CloneNotSupportedException {
        return (Person) super.clone();
    }
}
public static class Baby implements Cloneable {
    public String name;
    public int age;
    public String[] names;
    public Baby(String name, int age, String[] names) {
        this.name = name;
        this.age = age;
        this.names = names;
    }
    @Override
    public String toString() {
        return "Baby{" + "name='" + name + '\'' + ", age=" + age + ", names=" + Arrays.toString(names) + '}';
    }
    @Override
    protected Baby clone() throws CloneNotSupportedException {
        return (Baby) super.clone();
    }
}
public static void main(String[] args) throws CloneNotSupportedException {
    Person person = new Person("person", 10);
    person.names = new String[]{"qq", "www"};
    person.baby = new Baby("baby", 20, new String[]{"qqqqq", "wwwww"});
    person.names2.add("1111");
    person.names2.add("2222");
    //  對克隆后的數(shù)據(jù)進行更改
    Person clone = person.clone();
    clone.name = "person1";
    clone.age = 23;
    clone.names2.add("3333");
    clone.names = new String[]{"111", "222"};

    clone.baby.name = "baby1";
    clone.baby.names = new String[]{"ttttt"};
    
    System.out.println(person.toString());
    System.out.println(clone.toString());
}

對應輸出

Person{name='person', age=10, names=[qq, www], baby=Baby{name='baby1', age=20, names=[ttttt]}, names2=[1111, 2222, 3333]}
Person{name='person1', age=23, names=[111, 222], baby=Baby{name='baby1', age=20, names=[ttttt]}, names2=[1111, 2222, 3333]}

結論

發(fā)現(xiàn)，在對克隆的數(shù)據(jù)進行數(shù)據(jù)更改后：

• 基本數(shù)據(jù)類型，String，基本數(shù)據(jù)類型和String對應的數(shù)組，復制了一份，更改不會影響原始數(shù)據(jù)；
• 引用類型數(shù)據(jù)，只是復制了引用地址，對克隆后的引用數(shù)據(jù)類型操作，原始數(shù)據(jù)也會變，如測試中的Baby對象；

深克隆

對引用數(shù)據(jù)類型創(chuàng)建新的對象，并將屬性克隆過去；需要遞歸克隆引用數(shù)據(jù)類型；

實現(xiàn)方式

public static class Person implements Cloneable {
    @Override
    protected Person clone() throws CloneNotSupportedException {
        Person person = (Person) super.clone();
        person.baby = baby.clone();
        person.names2 = (ArrayList<String>) names2.clone();
        return person;
    }
}

例如

將上面淺克隆的例子中的clone方法改成

public static class Person implements Cloneable {
    @Override
    protected Person clone() throws CloneNotSupportedException {
        Person person = (Person) super.clone();
        person.baby = baby.clone();
        person.names2 = (ArrayList<String>) names2.clone();
        return person;
    }
}

輸出

Person{name='person', age=10, names=[qq, www], baby=Baby{name='baby', age=20, names=[qqqqq, wwwww]}, names2=[1111, 2222]}
Person{name='person1', age=23, names=[111, 222], baby=Baby{name='baby1', age=20, names=[ttttt]}, names2=[1111, 2222, 3333]}

結論

• 引用數(shù)據(jù)類型創(chuàng)建了一份新的數(shù)據(jù)，對克隆的數(shù)據(jù)更改，不會影響原始數(shù)據(jù)；

注意

1. 必須實現(xiàn)Cloneable接口，否則調(diào)用clone方法拋出異常

Object的clone方法的實現(xiàn)

protected Object clone() throws CloneNotSupportedException {
   if (!(this instanceof Cloneable)) {
       throw new CloneNotSupportedException("Class " + getClass().getName() +" doesn't implement Cloneable");
   }
   return internalClone();
}

 /*
 * Native helper method for cloning.
 */
@FastNative
private native Object internalClone();

2. 深克隆時子類也要復寫clone方法

父類實現(xiàn)了clone方法，如果子類不覆寫，那么子類只能淺克隆；