32、单例类

class Singleton{
    //使用一个变量来缓存曾经创建的实例
    private static Singleton instance;
    //对构造器使用private修饰，隐藏该构造器
    private Singleton(){}
    //该方法用来获取实例，保证只产生一个Singleton对象
    public static Singleton getInstance(){
        if(instance==null){
            instance=new Singleton();
        }
        return instance;
    }
}

public class SingletonTest {
    public static void main(String[] args) {
        Singleton s1=Singleton.getInstance();
        Singleton s2=Singleton.getInstance();
        System.out.println(s1==s2);
    }
}