class Singleton
{
private static Singleton s;
Singleton()
{
}
private static Singleton getSingleton()
{
if(s!=null)//是关键
s=new Singleton();
return s;
}
public static void main(String []args)
{
Singleton s1=Singleton.getSingleton();
Singleton s2=Singleton.getSingleton();
if(s1==s2)
{
System.out.println("只能新创建一个对象");
}
}
}