java惯用设计模式之享元模式

java常用设计模式之享元模式

------------------------------ 享元模式(Flyweight) -------------------------------
(1)
主要用于创建对象时，运用共享技术，减少对象对内存的占用.一个提高程序效率和性能的模式,会大大加快程序的运

行速度.
就是说在一个系统中如果有多个相同的对象，那么只共享一份就可以了，不必每个都去实例化一个对象。

Flyweight(享元)模式中常出现Factory模式。Flyweight的内部状态是用来共享的,Flyweight factory负责维护一个对

象存储池（Flyweight Pool）来存放内部状态的对象。

Flyweight的关键思路,在于:
新建对象时:
先到hashtable中进行获取-->判断取得对象是否为空-->若是,则新建此对象,且放回hashtable -->若存在,则共享原来

的对象.

(2)
实例: (与静态工厂模式进行对比)
public interface Car {
public void showCarName();

}

class BMWCar implements Car
{
public void showCarName()
{
System.out.println("this is the BMWCar .");
}
}

class FordCar implements Car
{
public void showCarName()
{
System.out.println("this is the FordCar .");
}
}

class CarFactory
{
public static Car car;
public static Car getCar(String name)
{
  if("BMW".equals(name))
  {
   car = new BMWCar();
  }
  if("Ford".equals(name))
  {
   car = new FordCar();
  }
  return car;
}
}

class CarFlyWeightFactory
{
    public Car car;
    private Hashtable<String,Car> carPool=new Hashtable<String,Car>();
public Car getCar(String name)
{
  if("BMW".equals(name))
  {
   car=carPool.get(name);
   if(car==null)
   {
    car=new BMWCar();
    carPool.put(name, car);
   }
  }

  if("Ford".equals(name))
  {
   car=carPool.get(name);
   if(car==null)
   {
    car=new FordCar();
    carPool.put(name, car);
   }
  }
  return car;
}
        public int getNumber(){ return carPool.getSize(); }
}

public class Test {

public static void main(String[] args) {
  CarFlyWeightFactory carFlyWeightFactory=new CarFlyWeightFactory();
  Car carf1=carFlyWeightFactory.getCar("Ford");
  carf1.showCarName();
  Car carf2=carFlyWeightFactory.getCar("Ford");
  carf2.showCarName();
  if(carf1==carf2)
  {
   System.out.println("同一部车来的");
  }
  else
  {
   System.out.println("不同一部车来的");
  }
  System.out.println("车的数量是:"+carFlyWeightFactory.getNumber());
}
}

输出:
this is the FordCar .
this is the FordCar .
同一部车来的

转自:http://shenzhenchufa.blog.51cto.com/730213/161581

java惯用设计模式之享元模式

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