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  • 【设计模式】-结构型-6-享元模式

    主要角色

    1. 抽象享元角色(Flyweight):是所有的具体享元类的基类,为具体享元规范需要实现的公共接口,非享元的外部状态以参数的形式通过方法传入。
    2. 具体享元(Concrete Flyweight)角色:实现抽象享元角色中所规定的接口。
    3. 非享元(Unsharable Flyweight)角色:是不可以共享的外部状态,它以参数的形式注入具体享元的相关方法中。
    4. 享元工厂(Flyweight Factory)角色:负责创建和管理享元角色。当客户对象请求一个享元对象时,享元工厂检査系统中是否存在符合要求的享元对象,如果存在则提供给客户;如果不存在的话,则创建一个新的享元对象。

    代码示例

    package flyweight;
    import java.util.HashMap;
    public class FlyweightPattern
    {
        public static void main(String[] args)
        {
            FlyweightFactory factory=new FlyweightFactory();
            Flyweight f01=factory.getFlyweight("a");
            Flyweight f02=factory.getFlyweight("a");
            Flyweight f03=factory.getFlyweight("a");
            Flyweight f11=factory.getFlyweight("b");
            Flyweight f12=factory.getFlyweight("b");       
            f01.operation(new UnsharedConcreteFlyweight("第1次调用a。"));       
            f02.operation(new UnsharedConcreteFlyweight("第2次调用a。"));       
            f03.operation(new UnsharedConcreteFlyweight("第3次调用a。"));       
            f11.operation(new UnsharedConcreteFlyweight("第1次调用b。"));       
            f12.operation(new UnsharedConcreteFlyweight("第2次调用b。"));
        }
    }
    //非享元角色
    class UnsharedConcreteFlyweight
    {
        private String info;
        UnsharedConcreteFlyweight(String info)
        {
            this.info=info;
        }
        public String getInfo()
        {
            return info;
        }
        public void setInfo(String info)
        {
            this.info=info;
        }
    }
    //抽象享元角色
    interface Flyweight
    {
        public void operation(UnsharedConcreteFlyweight state);
    }
    //具体享元角色
    class ConcreteFlyweight implements Flyweight
    {
        private String key;
        ConcreteFlyweight(String key)
        {
            this.key=key;
            System.out.println("具体享元"+key+"被创建!");
        }
        public void operation(UnsharedConcreteFlyweight outState)
        {
            System.out.print("具体享元"+key+"被调用,");
            System.out.println("非享元信息是:"+outState.getInfo());
        }
    }
    //享元工厂角色
    class FlyweightFactory
    {
        private HashMap<String, Flyweight> flyweights=new HashMap<String, Flyweight>();
        public Flyweight getFlyweight(String key)
        {
            Flyweight flyweight=(Flyweight)flyweights.get(key);
            if(flyweight!=null)
            {
                System.out.println("具体享元"+key+"已经存在,被成功获取!");
            }
            else
            {
                flyweight=new ConcreteFlyweight(key);
                flyweights.put(key, flyweight);
            }
            return flyweight;
        }
    }
    
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  • 原文地址:https://www.cnblogs.com/tuofan/p/12335836.html
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