手写一个简单的单例

懒汉式

/**
*懒汉式
*/
public class Singleton{
	private static Singleton singleton = new Singleton();
	private Singleton(){}
	public static Singleton getSingleton(){
		return singleton;
	}
}

饿汉式

/**
* 饿汉式
*/
public class Singleton{
	private static Singleton singleton = null;
	private Singleton(){}
	public static synchronized Singleton getSingleton(){
		if(singleton==null){
			singleton = new Singleton();
		}
		return singleton;
	}
}