责任链模式

责任链模式持有一个下级对象，并在实现方法里决定处理或交给下级处理，客户提交一个请求给责任链，无需关心在哪个节点处理了这个请求，适用于有层级的请求，Android的事件分发的思路就是这种模式。示例如下：

public class Responsibility {
    public static void main(String[] args){
        Responsibility responsibility = new Responsibility();
        IBuyFood boy = responsibility.new Boy();
        IBuyFood father = responsibility.new Father();
        IBuyFood mother = responsibility.new Mother();
        IBuyFood clerk = responsibility.new Clerk();
        boy.setiBuyFood(father);
        father.setiBuyFood(mother);
        mother.setiBuyFood(clerk);
        boy.buy(120);
    }

    abstract class IBuyFood{
        private IBuyFood iBuyFood;

        public IBuyFood getiBuyFood() {
            return iBuyFood;
        }

        public void setiBuyFood(IBuyFood iBuyFood) {
            this.iBuyFood = iBuyFood;
        }

        public abstract void buy(int money);
    }

    class Boy extends IBuyFood{
        @Override
        public void buy(int money) {
            if(getiBuyFood()!=null){
                System.out.println("我想用"+money+"元买个蛋糕");
                getiBuyFood().buy(money);
            }else{
                System.out.println("想吃个蛋糕都不知道找谁买");
            }
        }
    }

    class Father extends IBuyFood{
        @Override
        public void buy(int money) {
            if(money<100){
                System.out.println("去买吧，你老爹就这么点零花钱了");
            }else{
                if(getiBuyFood()!=null){
                    System.out.println("你爹做不了主，问你妈去");
                    getiBuyFood().buy(money);
                }else{
                    System.out.println("你爹还想吃蛋糕呢，找谁买去");
                }
            }
        }
    }

    class Mother extends IBuyFood{
        @Override
        public void buy(int money) {
            if(money<200){
                if(getiBuyFood()!=null){
                    System.out.println("去买吧，妈给你");
                    getiBuyFood().buy(money);
                }else{
                    System.out.println("哪来的卖蛋糕的");
                }
            }else{
                System.out.println("小兔崽子，又吃蛋糕");
            }
        }
    }

    class Clerk extends IBuyFood{
        @Override
        public void buy(int money) {
            if(money>150){
                System.out.println("给你蛋糕");
            }else{
                System.out.println("这点钱买不起蛋糕的");
            }
        }
    }
}