多线程的懒汉式

/*
单例设计模式
*/
//饿汉式
/*
class Single
{
private static final Single s = new Single();
private Single(){}
public static Single getInstance()
{
return s;
}
}
*/
//多线程的懒汉式
class Single
{
private static Single s = null;
private Single(){}
public static Single getInstance()
{
if(s == null)
{
synchronized(Single.class)
{
if(s == null)
s = new Single();

}
}
return s;
}
}
class Test_11_14
{
public static void main(String[] args)
{
System.out.println("Hello Wolrd");
}
}