http://alicharles.com/article/jdk-flyweight-pattern/

http://www.cnblogs.com/java-my-life/archive/2012/04/26/2468499.html

示例:

import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;
public class Test {
/**
* 复合的享元模式: 复合享元是不能共享的。但是复合享元是可以分解为可共享的单纯享元。
*/
public static void main(String[] args) {
FlyweightFactory f = new FlyweightFactory();
Flyweight fly = f.factory("aba");
fly.operation("charles");
f.checkFlyweight();
}
}
/**
* 抽象享元
*/
abstract class Flyweight {
public abstract void operation(String extrinsicState);
}
/**
* 具体享元
*/
class ConcreteFlyweight extends Flyweight {
private Character inState;
public ConcreteFlyweight(Character inState) {
this.inState = inState;
}
/**
* 外蕴状态改变方法行为，但不会改变内蕴状态
*/
@Override
public void operation(String extState) {
String str = "inState:" + inState + ";extState:" + extState;
System.out.println(str);
}
}
/**
* 复合享元
*/
class CompositeFlyweight extends Flyweight {
private Map<Character, Flyweight> map;
public CompositeFlyweight() {
map = new HashMap<Character, Flyweight>();
}
public void add(Character c, Flyweight fly) {
map.put(c, fly);
}
@Override
public void operation(String extState) {
Iterator<Map.Entry<Character, Flyweight>> it = map.entrySet().iterator();
while (it.hasNext()) {
Map.Entry<Character, Flyweight> entry = it.next();
Flyweight fly = entry.getValue();
fly.operation(extState);
}
}
}
/**
* 享元工厂
*/
class FlyweightFactory {
private Map<Character, Flyweight> map;
public FlyweightFactory() {
map = new HashMap<Character, Flyweight>();
}
/**
* 单纯享元工厂
*/
public Flyweight factory(Character state) {
Flyweight flyweight;
if (map.containsKey(state)) {
flyweight = map.get(state);
} else {
flyweight = new ConcreteFlyweight(state);
map.put(state, flyweight);
}
return flyweight;
}
/**
* 复合享元工厂此处Character的复合类型恰好是String，当无此巧合时，可使用List等聚集类型传入.
*/
public Flyweight factory(String compositeState) {
CompositeFlyweight composite = new CompositeFlyweight();
for (int i = 0; i < compositeState.length(); i++) {
Character c = new Character(compositeState.charAt(i));
composite.add(c, this.factory(c));
}
return composite;
}
/**
* 辅助方法
*/
public void checkFlyweight() {
Iterator<Map.Entry<Character, Flyweight>> it = map.entrySet().iterator();
System.out.println("checkFlyweight:");
while (it.hasNext()) {
Map.Entry<Character, Flyweight> entry = it.next();
Character key = entry.getKey();
System.out.println("key:" + key);
}
}
}

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