题目

实现猫狗队列

代码实现

//宠物类
class Pet {
    private String type;

    public Pet(String type) {
        this.type = type;
    }

    public String getPetType() {
        return this.type;
    }
}

//狗类
class Dog extends Pet {
    public Dog() {
        super("dog");
    }
}

//猫类
class Cat extends Pet {
    public Cat() {
        super("cat");
    }
}

//添加了时间戳的宠物类
class PetEnterQueue {
    private Pet pet;
    private long count;

    public PetEnterQueue(Pet pet, long count) {
        this.pet = pet;
        this.count = count;
    }

    public Pet getPet() {
        return this.pet;
    }

    public long getCount() {
        return this.count;
    }
}

//猫狗类
public class DogCatQueue {
    private Queue<PetEnterQueue> dogQ;
    private Queue<PetEnterQueue> catQ;
    private long count;

    public DogCatQueue() {
        this.dogQ = new LinkedList<PetEnterQueue>();
        this.catQ = new LinkedList<PetEnterQueue>();
        this.count = 0;
    }

    //将cat类或dog类的实例放入队列中
    public void add(Pet pet) {
        if (pet.getPetType().equals("dog")) {
            this.dogQ.add(new PetEnterQueue(pet, this.count++));
        } else if (pet.getPetType().equals("cat")) {
            this.catQ.add(new PetEnterQueue(pet, this.count++));
        } else {
            throw new RuntimeException("err, not dog or cat");
        }
    }

    //将队列中所有的实例按照进队列的先后顺序依次弹出
    public Pet pollAll() {
        if (!isDogQueueEmpty() && !isCatQueueEmpty()) {
            if (this.dogQ.peek().getCount() < this.catQ.peek().getCount()) {
                return this.dogQ.poll().getPet();
            } else {
                return this.catQ.poll().getPet();
            }
        } else if (!this.isDogQueueEmpty()) {
            return this.dogQ.poll().getPet();
        } else if (!this.isCatQueueEmpty()) {
            return this.catQ.poll().getPet();
        } else {
            throw new RuntimeException("err, queue is empty!");
        }
    }

    //将队列中dog类的实例按照进队列的先后顺序依次弹出
    public Dog pollDog() {
        if (!this.isDogQueueEmpty()) {
            return (Dog) this.dogQ.poll().getPet();
        } else {
            throw new RuntimeException("Dog queue is empty!");
        }
    }

    //将队列中cat类的实例按照进队列的先后顺序依次弹出
    public Cat pollCat() {
        if (!this.isCatQueueEmpty()) {
            return (Cat) this.catQ.poll().getPet();
        } else {
            throw new RuntimeException("Cat queue is empty!");
        }
    }

    //检查队列中是否还有dog或者cat的实例
    public boolean isEmpty() {
        return isDogQueueEmpty() && isCatQueueEmpty();
    }

    //检查队列中是否有dog类的实例
    public boolean isDogQueueEmpty() {
        return this.dogQ.isEmpty();
    }

    //检查队列中是否有cat类的实例
    public boolean isCatQueueEmpty() {
        return this.catQ.isEmpty();
    }
}