单例模式之懒汉式和饿汉式

//懒汉式
public class Singleton {
    private Singleton() {
    }
    private static Singleton singleton = null;
//静态工厂方法
    public static Singleton getInstance() {
        if (singleton == null) {
            singleton = new Singleton();
        }
        return singleton;
    }

}

  //饿汉式
public class Singleton {  

    private Singleton(){}

    private static final Singleton singleton=new Singleton();
//静态工厂方法
    public static Singleton getInstance(){
        return singleton;
    }
}