单例模式的两种写法

/*饿汉式*/

class Single(){

private static final Single sl = new Single();

private Single(){}

public static Single getInstance(){

return sl;

}

}

/*懒汉式  

 * 也叫做延迟加载*/

class Single()

{

private static Single sl=null;

private Single(){}

public static synchronized Single getInstance()

{

if(sl==null)

{

synchronized(Single.class)

{//静态同步代码块

if(sl==null)

sl=new Single();

}

}

}

}