享元模式具体事例（元素化合物）带你参透享元模式的原理与作用
相同元素的化合物都是由几种不同的元素组成的，只是含有元素的个数不同，以下是我设计的几个接口和类，能让具有形同元素的化合物共享相同元素在内存中所占的空间。
===========================享元接口==============================
package com.zqs.flyweight;
/**
* 享元接口
* @author Administrator
*
*/
public interface Flyweight {
/**
* 参数：传递进来外部的数据
* 为了扩展方便（根据具体实现传递），所以此处参数传递选择java可变参数
*/
public void operation(Object... extrinsicObjects);
}
===========================享元接口==============================
===========================享元工厂==============================
package com.zqs.flyweight;
import java.util.HashMap;
/**
* 享元工厂类，采用单例模式
* @author zqs
*
*/
public class FlyweightFactory {
//享元池
private HashMap
private static FlyweightFactory instance = new FlyweightFactory();
private FlyweightFactory() {
flyweightPool = new HashMap
}
public static FlyweightFactory getInstance() {
return instance;
}
/**
* 获取享元的方法，享元已经存在就从享元池中拿，不存在就创建一个
* @param key 化合物中的元素字符加起来组成的字符串
* @return
*/
public Flyweight getFlyweight(String key) {
Flyweight flyweight = flyweightPool.get(key);
if(flyweight == null) {
flyweight = new CompoundFlyweight(key);
flyweightPool.put(key, flyweight);
}
return flyweight;
}
/**
* 具体享元类作为工厂类的一个内部类，构造方法私有化
* 只有工厂才能产生享元，用户无法自己构造
* 此处是实现享元的一个具体类，化合物类
* @author zqs
*
*/
class CompoundFlyweight implements Flyweight {
private char[] elements;
private CompoundFlyweight(String key) {
int length = key.length();
elements = new char[length];
for(int i=0; i
}
}
/**
* 此处具体实现，不同的具体享元对象不同
*/
@Override
public void operation(Object... extrinsicObjects) {
//化合物的名称
String name = (String)extrinsicObjects[0];
//元素的个数
int[] counts = (int[])extrinsicObjects[1];
System.out.println("============================================================");
System.out.println("化合物的名字是：" + name + ",共含有" + counts.length + "种元素");
//每种元素的个数
for(int i=0; i
}
}
}
}
===========================享元工厂==============================
=============具体化合物（关联共享的享元对象）========================
package com.zqs.flyweight;
/**
* 具体化合物
* @author Administrator
*
*/
public class Compound {
//化合物名称
private String name;
//元素种类 化合物中的元素字符加起来组成的字符串
private String key;
//内部共享对象，即享元对象
private Flyweight flyweight;
//每种元素的个数
private int[] counts;
/**
* 不提供无参构造函数
* @param name
* @param key
* @param flyweight
* @param counts
*/
public Compound(String name, String key, Flyweight flyweight, int[] counts) {
super();
this.name = name;
this.key = key;
this.flyweight = flyweight;
this.counts = counts;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public String getKey() {
return key;
}
public void setKey(String key) {
this.key = key;
}
public Flyweight getFlyweight() {
return flyweight;
}
public void setFlyweight(Flyweight flyweight) {
this.flyweight = flyweight;
}
public int[] getCounts() {
return counts;
}
public void setCounts(int[] counts) {
this.counts = counts;
}
}
=============具体化合物（关联共享的享元对象）========================
===========================测试程序==============================
package com.zqs.flyweight;
/**
* 测试程序
* @author Administrator
*
*/
public class Application {
/**
* @param args
*/
public static void main(String[] args) {
FlyweightFactory factory = FlyweightFactory.getInstance();
String hoKey = "ho";
String chKey = "ch";
//水
Flyweight h2oCompoundFlyweight = factory.getFlyweight(hoKey);
Compound h2oCompound = new Compound("水", hoKey, h2oCompoundFlyweight, new int[]{2, 1});
h2oCompound.getFlyweight().operation(h2oCompound.getName(), h2oCompound.getCounts());
//双氧水
Flyweight h2o2CompoundFlyweight = factory.getFlyweight(hoKey);
Compound h2o2Compound = new Compound("双氧水", hoKey, h2o2CompoundFlyweight, new int[]{2, 2});
h2o2Compound.getFlyweight().operation(h2o2Compound.getName(), h2o2Compound.getCounts());
//含有同种元素的化合物共享享元池中的享元（享元池在工厂内部），所有打印的地址为true
System.out.println("水(h2o)与双氧水(h2o2)是否共享享元：" + (h2oCompound.getFlyweight() == h2o2Compound.getFlyweight()));
//甲烷
Flyweight ch4CompoundFlyweight = factory.getFlyweight(chKey);
Compound ch4Compound = new Compound("甲烷", chKey, ch4CompoundFlyweight, new int[]{1, 4});
h2o2Compound.getFlyweight().operation(ch4Compound.getName(), ch4Compound.getCounts());
//含有不同种元素的化合物不共享享元池中的享元（享元池在工厂内部），所有打印的地址为false
System.out.println("水(h2o)与甲烷(ch4)是否共享享元：" + (h2oCompound.getFlyweight() == ch4Compound.getFlyweight()));
}
}
===========================测试程序==============================
===========================测试结果==============================
===========================测试结果==============================