享元模式

1. 享元模式结构图

   

2. 示例代码

   // 抽象享元角色
   public interface Flyweight {
   
       void doSomething();
   }
   
   // 具体享元角色
   public class ConcreteFlyweight implements Flyweight{
   
       private String status;
   
       public ConcreteFlyweight(String status) {
           this.status = status;
       }
   
       @Override
       public void doSomething() {
           System.out.println("开始工作，状态：" + status);
       }
   }
   
   //　享元工厂
   public class FlyweightFactory {
       private Map<String, Flyweight> pool = new HashMap<>();
   
       public Flyweight getFlyweight(String status){
           if (!pool.containsKey(status)){
               System.out.println("新建享元模式对象");
               pool.put(status, new ConcreteFlyweight(status));
           }
           return pool.get(status);
       }
   
       public int getSize(){
           return pool.size();
       }
   }
   
   
   // 测试类
   public class FlyweightTest {
   
       public static void main(String[] args) {
           FlyweightFactory factory = new FlyweightFactory();
           Flyweight f1 = factory.getFlyweight("忙碌");
           Flyweight f2 = factory.getFlyweight("轻松");
           Flyweight f3 = factory.getFlyweight("魔域");
           Flyweight f4 = factory.getFlyweight("忙碌");
           System.out.println(factory.getSize());
       }
   }
   
   

3. 总结：

   优点：减少了对象的创建，降低了资源的消耗，提供效率；

   缺点：关注内外部状态，关注线程安全问题，使系统逻辑复杂化．