java单例模式

java单例模式分为两种：饱汉式(懒汉式)、饿汉式

1.饱汉式：(在调用getInstance时创建对象)

public class Singleton {

  private volatile static Singleton instance = null;
	
	public Singleton(){
	}
	
	public static Singleton getInstance(){
		if(instance==null){
			instance=new Singleton();
		}
		return instance;
	}

}

2.饿汉式：(在类加载时创建单例对象)

public class Singleton {

   private volatile static Singleton instance=new Singleton();
	
	public Singleton(){
	}
	
	public static Singleton getInstance(){
		return instance;
	}

}