享元模式

1. 享元角色抽象类

public abstract class AbstractFlyweight {
    //外部状态
    private final String extrinsic;
    //内部状态
    private String intrinsic;
    public AbstractFlyweight(String extrinsic) {
        this.extrinsic = extrinsic;
    }
    public String getIntrinsic() {
        return intrinsic;
    }
    public void setIntrinsic(String intrinsic) {
        this.intrinsic = intrinsic;
    }
    //公共方法
    protected abstract void operate();
}

2. 享元角色抽象类实现类

public class ConcreteFlyweight extends AbstractFlyweight {
    public ConcreteFlyweight(String extrinsic) {
        super(extrinsic);
    }
    @Override
    protected void operate() {
        //具体逻辑
    }
}

3. 享元角色工厂类

public class FlyweightFactory {
    //享元池
    private static Map<String, AbstractFlyweight> pool = new HashMap<>();
    //获取享元角色
    public static AbstractFlyweight getFlyweight(String extrinsic) {
        AbstractFlyweight flyweight;
        if (pool.containsKey(extrinsic)) {
            flyweight = pool.get(extrinsic);
        } else {
            flyweight = new ConcreteFlyweight(extrinsic);
            pool.put(extrinsic, flyweight);
        }
        return flyweight;
    }
}

4. 场景使用

    AbstractFlyweight flyweight =  FlyweightFactory.getFlyweight("key");
    flyweight.operate();