设计模式之享元模式

享元模式

运用共享技术有效的支持大量细粒度的对象。

FlyWeight

package com.hml.flyweight;

public abstract class FlyWeight {
public abstract void operation(int p);
}

ConcreateFlyWeight

package com.hml.flyweight;

public class ConcreateFlyWeight extends FlyWeight {

@Override
public void operation(int p) {
System.out.println("具体的类：" + p);
}

}

FlyWeigthFactory

package com.hml.flyweight;

import java.util.HashMap;
import java.util.Map;

public class FlyWeigthFactory {
private static Map<String, FlyWeight> flyweigths = new HashMap<String, FlyWeight>();

static {
flyweigths.put("x", new ConcreateFlyWeight());
flyweigths.put("y", new ConcreateFlyWeight());
flyweigths.put("z", new ConcreateFlyWeight());
}

public static FlyWeight getFlyWeight(String key) {
return flyweigths.get(key);
}
}

Test

package com.hml.flyweight;

public class Test {
public static void main(String[] args) {

FlyWeigthFactory factory = new FlyWeigthFactory();
FlyWeight f = factory.getFlyWeight("x");
f.operation(22);
f = factory.getFlyWeight("y");
f.operation(22);
}
}

类图

享元模式可以避免大量非常相似类的开销。在程序设计中，有时需要生成大量细粒度的类的实例来表示数据。如果能发现这些实例除了几个参数外基本上相同，有时就能够大幅度的减少需要实例化的类的数量。如果能把参数移到类的外面，在方法调用时传递进来，就可以可以通过共享减少单个实例的数据量。