java基础面试题：写clone()方法时，通常都有一行…

2018-06-18 03:44:30来源：未知阅读 ()

clone()方法与new constructor()构造器创建对象不同是克隆一个新的对象

package com.swift;

public class Clone_Test {

    public static void main(String[] args) {
        Person p = new Person(23, "zhang");
        Person p1 = p;
        
        System.out.println(p);
        System.out.println(p1);
    }

}

class Person{
    private int age;
    private String name;
    public Person(int age, String name) {
        this.age = age;
        this.name = name;
    }
}

Person p1=p; 这个不是对象的克隆是引用的复制因为p p1的地址相同

克隆的方法

实现Cloneable接口覆写clone()方法克隆要先克隆父类所以要super.clone();

package com.swift;

public class Clone_Test {

    public static void main(String[] args) throws CloneNotSupportedException {
        Person p = new Person(23, "zhang");
        Person p1 = (Person) p.clone();
        
        System.out.println(p);
        System.out.println(p1);
    }
}

class Person implements Cloneable{
    private int age;
    private String name;
    public Person(int age, String name) {
        this.age = age;
        this.name = name;
    }
    @Override
    protected Object clone() throws CloneNotSupportedException {
        return super.clone();
    }
}

这是克隆的p1和p的内存地址已经不同

如果要克隆的对象中还包含其他对象

则克隆后的对象是 浅拷贝 的而不是 深拷贝 的克隆前后对象中的对象都是同一个对象

如果要深拷贝则要在clone() 方法中把对象中的对象也进行克隆

class Body implements Cloneable{  
    public Head head;  
    public Body() {}  
    public Body(Head head) {this.head = head;}  
  
    @Override  
    protected Object clone() throws CloneNotSupportedException {  
        Body newBody =  (Body) super.clone();  //克隆了body
        newBody.head = (Head) head.clone();   //深入克隆newBody中的对象
        return newBody;  
    }  
      
}