享元模式

享元模式：运用共享技术有效地支持大量细粒度的对象，主要是通过HashMap对键是否存在的判断。以下是例子：

public class FlyweightImpl implements Flyweight{  

public void action(int arg) {

System.out.println("参数值"+arg); } }

 

public class FlyweightFactory {  

private static Map flyweights = new HashMap();

public static Flyweight getFlyweight(String key){

if(flyweights.get(key)==null){

flyweights.put(key, new FlyweightImpl()); }

return (Flyweight) flyweights.get(key); }

public static int getSize(){ return flyweights.size(); } }

 

//测试类

public class Test {

public static void main(String[] args) {

Flyweight fly1 = FlyweightFactory.getFlyweight("a");

fly1.action(1);

Flyweight fly2 = FlyweightFactory.getFlyweight("a");

fly1.action(2);

System.out.println(fly1==fly2);

Flyweight fly3 = FlyweightFactory.getFlyweight("c");

fly1.action(3);

Flyweight fly4 = FlyweightFactory.getFlyweight("d");

fly1.action(4);

System.out.println(FlyweightFactory.getSize()); } }