浅克隆
只复制了基本数据类型和String数据类型以及对应的数组类型，其他引用数据类型只是复制了引用地址；
使用方式
实现Cloneable接口，然后重写clone方法，调用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");
// 对克隆后的数据进行更改
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());
}
对应输出
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]}
结论
发现，在对克隆的数据进行数据更改后：
- 基本数据类型，String，基本数据类型和String对应的数组，复制了一份，更改不会影响原始数据；
- 引用类型数据，只是复制了引用地址，对克隆后的引用数据类型操作，原始数据也会变，如测试中的Baby对象；
深克隆
对引用数据类型创建新的对象，并将属性克隆过去；需要递归克隆引用数据类型；
实现方式
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
将上面浅克隆的例子中的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;
}
}
输出
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]}
结论
- 引用数据类型创建了一份新的数据，对克隆的数据更改，不会影响原始数据；
注意
1. 必须实现Cloneable接口，否则调用clone方法抛出异常
Object的clone方法的实现
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. 深克隆时子类也要复写clone方法
父类实现了clone方法，如果子类不覆写，那么子类只能浅克隆；
