java設計模式之享元模式

①UML設計

②定義及使用場景：利用共享的方式解決大量創建銷燬導致額外開銷

③示例：

/**
 * 構建享元角色接口
 */
public interface Flyweight{
   void action();
}

/**
 * 構建具體享元類
 */
public class ConcreteFlyweight implements Flyweight{
   @Override
   public void action(){
     System.out.println("享元模式");
}
}

/**
 * 構建享元工廠
 */
public class FactoryFlyweight{
   static Map<String,Flyweight> flyweightMap = Maps.newConcurrentMap();//共享池
   public static Flyweight getFlyweight(String key){
   Flyweight flyweight = flyweightMap.get(key);//根據key先去共享池中查找是否已有需要的對象
   if(null == flyweight){
   flyweightMap.put(key,new ConcreteFlyweight());//沒有需要的對象就重新創建一個，並保存到共享池中
   }
   return flyweightMap.get(key);
   }
   public static int getSize(){
   return flyweightMap.size();
   }
}

public class Test{
  public static void main(String args[]){
  Flyweight fw1 = FactoryFlyweight.getFlyweight("1");
  fw1.action();
  Flyweight fw2 = FactoryFlyweight.getFlyweight("2");
  fw2.action();
  Flyweight fw3 = FactoryFlyweight.getFlyweight("1");
  fw3.action();
  System.out.println(FactoryFlyweight.getSize());//實際值保存了兩個對象，所以爲2
}}