java的clone

一、clone的用法：

package chatRoom.F5;
 
class Person implements Cloneable{//1.
    public String name;
    public Person(String name) {
        this.name = name;
    }
 
    //2.
    protected Person clone() throws CloneNotSupportedException {
        return (Person)super.clone();//重写Object类的clone
    }
}
 
//clone():  复制对象。
public class CloneDemo {
    public static void main(String[] args) throws CloneNotSupportedException {
        Person p1=new Person("zs");
        Person p2=p1.clone();//p2表示复制出来的第二份儿对象
    }
}

二、clone的浅克隆：

如果具有引用类型成员变量的类，单纯的重写了clone方法。 则调用clone方法进行对象克隆时就是浅克隆(只是克隆了此类对象，内部的引用类型属性指向的对象没有被克隆)。

package chatRoom.F5;
 
class Person implements Cloneable{//1.
    public String name;
    public Person(String name) {
        this.name = name;
    }
 
    //2.
    protected Person clone() throws CloneNotSupportedException {
        return (Person)super.clone();//重写Object类的clone
    }
}
 
 
 
class ClassRoom implements Cloneable{
    int id;
    Person p1;
    protected ClassRoom clone() throws CloneNotSupportedException {
        return (ClassRoom)super.clone();//浅克隆
    }
}
 
 
 
public class CloneDemo {
    public static void main(String[] args) throws CloneNotSupportedException {
        ClassRoom c=new ClassRoom();//第一个ClassRoom
        c.p1=new Person("赵公明");
 
        //ClassRoom复制时，没有复制ClassRoom里边的Person对象
        ClassRoom d=c.clone();//第2个ClassRoom
 
        System.out.println(c.p1 ==  d.p1);
    }
}

三、clone的深克隆：

如果具有引用类型成员变量的类，此时若需要进行深克隆，则需要重写了clone方法，并在clone方法中调用引用类型成员变量的clone方法对引用类型变量指向的对象都进行克隆。 

package chatRoom.F5;
 
class Person implements Cloneable{//1.
    public String name;
    public Person(String name) {
        this.name = name;
    }
 
    //2.
    protected Person clone() throws CloneNotSupportedException {
        return (Person)super.clone();//重写Object类的clone
    }
}
 
 
 
class ClassRoom implements Cloneable{
    int id;
    Person p1;
    protected ClassRoom clone() throws CloneNotSupportedException {
        //改进：实现深克隆
        //方式：p1也调用clone
        ClassRoom c=(ClassRoom)super.clone();
        c.p1=p1.clone();
        return c;//浅克隆
        //return  (ClassRoom)super.clone();
    }
}
 
 
 
public class CloneDemo {
    public static void main(String[] args) throws CloneNotSupportedException {
        ClassRoom c=new ClassRoom();//第一个ClassRoom
        c.p1=new Person("赵公明");
 
        //ClassRoom复制时，没有复制ClassRoom里边的Person对象
        ClassRoom d=c.clone();//第2个ClassRoom
 
        //c中的p1对象的地址==d中的p1对象的地址
        System.out.println(c.p1 ==  d.p1);//false
    }
}