Java设计模式之单例模式实例详解【懒汉式与饿汉式】

package org.test.design.single;
/**
 * 懒汉式，单例模式
 * @author lushuaiyin
 *
 */
public class Loon {
  public static Loon loon=null;
  public static Loon getInstance(){
    if(loon==null){
      loon=new Loon();
    }
    return loon;
  }
}

package org.test.design.single;
/**
 * 饿汉式，单例模式
 * @author lushuaiyin
 *
 */
public class Hunger {
  public static Hunger hunger=new Hunger();
  public static Hunger getInstance(){
    return hunger;
  }
  //或者像下面使用
// public static Hunger hunger=null;
// static{
//   if(hunger==null){
//     hunger=new Hunger();
//   }
// }
// public static Hunger getInstance(){
//   return hunger;
// }
}

package org.test.design.single;
public class TestMain {
  /**
   * @param args
   */
  public static void main(String[] args) {
    //懒汉式，单例模式
    Loon loon=Loon.getInstance();
    System.out.println(loon==null);
    //饿汉式，单例模式
    Hunger hunger=Hunger.getInstance();
    System.out.println(hunger==null);
  }
}