[javaSE] 单例设计模式

class Single{
    private static Single single;
    public int num=1;
    private Single(){
    }
    public static Single getInstance(){
        if(single==null){
            single=new Single();
            System.out.println("对象只有一个");
        }
        return single;
    }
}
public class SingleDemo {
    /**
     * @param args
     */
    public static void main(String[] args) {
        Single s1=Single.getInstance();
        s1.num=2;
        Single s2=Single.getInstance();//只输出一次 "对象只有一个"
        System.out.println(s2.num);//此时输出2 说明是同一个对象
        
    }

}

<?php
class Single{
    private static $single;
    public $num=1;
    private function __construct(){

    }
    public static function getInstance(){
        if(Single::$single==null){
            Single::$single=new Single();
            echo "对象只有一个";
        }
        return Single::$single;
    }
    /*覆盖PHP的魔术方法*/
    private function __clone(){

    }

}
class SingleDemo{
    public static function main(){
        $obj1=Single::getInstance();
        $obj1->num=2;
        $obj2=Single::getInstance();//只输出一次 "对象只有一个"
        echo $obj2->num;// 此时输出2 说明是同一个对象
    }
}

SingleDemo::main();