享元模式-flyweight

运用共享技术有效地支持大量细粒度的对象

这里写图片描述
实际上就是通过一个容器存储对象，等到需要用的时候，再获取对象的引用

优点：

 减少对象数量，节省内存空间

缺点：

 维护共享对象需要额外开销，如需要专门设置一个线程来回收

代码：

Main

public class Main {

    public static void main(String[] args) {
        Flyweight f1,f2,f3,f4;
        FlyweightFactory factory=new FlyweightFactory();
        
        f1=factory.getFlyWeight("he");
        f2=factory.getFlyWeight("jd");
        f3=factory.getFlyWeight("he");
        f4=factory.getFlyWeight("he");
        
        f1.operation();f2.operation();f3.operation();f4.operation();
        System.out.println(factory.getFlyWeightSize());
    }

}

abs:FlyWeight

public abstract class Flyweight {
    public abstract void operation();
}

imp:ConcreteFlyWeight

public class ConcreteFlyweight extends Flyweight {

    private String name;
    public ConcreteFlyweight(String name){
        this.name=name;
    }
    @Override
    public void operation() {
        System.out.println("this is concrete flyweight name is "+this.name);
    }

}

imp:FlyWeightFactory

public class FlyweightFactory {
    
    private Map flyweight=new HashMap<Object, Object>();
    
    public Flyweight getFlyWeight(Object obj){
        Flyweight temp=(Flyweight) this.flyweight.get(obj);
        if(temp==null){
            temp=new ConcreteFlyweight((String) obj);
            this.flyweight.put(obj, temp);
        }
        return temp;
    }
    public int getFlyWeightSize(){
        return this.flyweight.size();
    }

}