24.面向对象-----单例模式

class Singleton{
    //1.私有化构造器
    private Singleton(){

    }

    //2.类内部提供一个当前类的私有实例
    //3.此实例也必须静态化
    private static Singleton single = new Singleton();

    //4.提供公共的静态方法返回当前对象
    public static Singleton getInstance(){
        return single;
    }
}

class Singleton{
    //1.私有化构造器
    private Singleton(){

    }

    //2.类内部提供一个当前类的私有实例
    //3.此实例也必须静态化
    private static Singleton single;

    //4.提供公共的静态方法返回当前对象
    public static Singleton getInstance(){
        if (single == null) {
            single = new Singleton();
        }
        return single;
    }
}