设计模式之单例模式的简单demo

 /*
  * 设计模式之单例模式的简单demo
  */
 class Single
 {
     /*
      * 创建一个本类对象。
      * 和get/set方法思想一样，类不能直接调用对象
      * 所以用private限制权限
      */
     private static Single s = new Single();
     /*
      * 构造函数私有化目的是为了只能产生一个对象
      */
     private Single(){}
     // 定义一个方法返回该对象，让外部可以调用。
     public static Single getInstance()
     {
         return s;
     }
 }

 class  SingleDemo
 {
     public static void main(String[] args)
     {
 //        Single s = Single.s;
         Single s1 = Single.getInstance();
         Single s2 = Single.getInstance();
         System.out.println(s1 == s2);
     }
 }

/*
 * 单例模式之饿汉式与懒汉式
 */

 //饿汉式
class Single
{
    private static Single s = new Single();

    private Single(){}

    public static Single getInstance()
    {
        return s;
    }
}
//懒汉式
class Single
{
    private static Single s = null;

    private Single(){}

    public static Single getInstance()
    {
        if (s == null)
        {
            s = new Single();
        }
        return s;
    }
}

 /*
  * 单例模式的小例子
  */
 class SuperMan
 {
     private String name;

     private static SuperMan man = new SuperMan("Clarke");

     private SuperMan (String name)
     {
         this.name = name;
     }

     public static SuperMan getInstance ()
     {
         return man;
     }

     public void setName(String name)
     {
         this.name = name;
     }
     public String getName()
     {
         return this.name;
     }
 }

 class SuperManDemo
 {
     public static void main(String[] args)
     {
         SuperMan s1 = SuperMan.getInstance();
         String name1 = s1.getName();
         System.out.println("name1 = " + name1);

         SuperMan s2 = SuperMan.getInstance();
         s2.setName("hero");
         String name2 = s2.getName();
         System.out.println("name2 = " + name2);
     }
 }