//单例模式之懒汉式class Singleton{ private static Singleton instance = null;  private Singleton(){ }  public static Singleton getSingleton(){  if(instance == null){   //同步代码块，保证安全性   synchronized(Singleton.class){    if(instance == null){     instance = new Singleton();    }   }  }    return instance; }}public class TestSingleton { /**  * @Title: main  * @Description:  * @param：  * @return void   * @user： wangzg  * @Date：2014-10-27  * @throws  */ public static void main(String[] args) {  // TODO Auto-generated method stub  Singleton singleton1 = Singleton.getSingleton();  Singleton singleton2 = Singleton.getSingleton();    System.out.println(singleton1 == singleton2); }}