享元模式

享元模式：通过池技术，对细粒度对象提供共享支持

优点：节省对象创建时间，减少内存开支，降低性能消耗

 

标准类图：

 抽象享元：

public abstract class FlyWeight {
	
	protected String externalAttribute;//external attribute
	
	public FlyWeight(String externalAttribute) {
		super();
		this.externalAttribute = externalAttribute;
	}

	protected abstract void operate();
	
	
}

 具体享元：

public class ConcreteFlyWeight extends FlyWeight {

	private String name;// internal attribute

	public String getName() {
		return name;
	}

	public void setName(String name) {
		this.name = name;
	}

	public ConcreteFlyWeight(String externalAttribute) {
		super(externalAttribute);
	}

	@Override
	protected void operate() {
		System.out.println("do some thing");
	}

}

 享元工厂：

public class FlyWeightFactory {
	
	private static Map<String, FlyWeight> pool = new HashMap<>();
	
	public static FlyWeight getFlyWeight(String key){
		if(pool.containsKey(key)){
			return pool.get(key);
		}else{
			ConcreteFlyWeight flyWeight = new ConcreteFlyWeight(key);
			pool.put(key, flyWeight);
			return flyWeight;
		}
	}
	
}

 场景类：

public class Client {
	
	public static void main(String[] args) {
		FlyWeight flyWeight1 = FlyWeightFactory.getFlyWeight("key1");
		FlyWeight flyWeight2 = FlyWeightFactory.getFlyWeight("key1");
		FlyWeight flyWeight3 = FlyWeightFactory.getFlyWeight("key2");
		System.out.println(flyWeight1);
		System.out.println(flyWeight2);
		System.out.println(flyWeight3);
	}
	
}