单例模式之内部静态类

public class Singleton
{
private Singleton(){ }

public static Singleton getInstance()
{
return Nested.instance;
}

//在第一次被引用时被加载
static class Nested
{
private static Singleton instance = new Singleton();
}

public static void main(String args[])
{
Singleton instance = Singleton.getInstance();
Singleton instance2 = Singleton.getInstance();
System.out.println(instance == instance2);
}
}