单例模式之懒汉式

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//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);

 }

}