java 数组实现队列和栈

一、数组实现队列

public class ArrayAsQueue {
    public static int head = 0;    //头指针
    public static int tail = 0;    //尾指针
    public static int count = 0;    //记录队列长度
    public static int[] array = new int[10];    //数组长度为10

    public static int offer(int num) {
        if (count == 10)
            return -1;
        array[tail] = num;
        tail = ++tail % 10;    //数组达到最后位置时，对其取模
        count++;
        return 1;
    }

    public static int poll() {
        if (count == 0)
            throw new RuntimeException();    //队列为空，抛出异常
        int tmp = array[head];
        head = ++head % 10;
        count--;
        return tmp;
    }
}

二、数组实现栈

public class ArrayAsStack {
    public static int index = -1;
    public static int[] array = new int[10];

    public static int push(int num) {
        if (index  < 9) {
            index++;
            array[index] = num;
            return 1;
        }
        return -1;
    }

    public static int pop() {
        if (index == -1)
            throw new RuntimeException();
        else {
            int tmp = array[index];
            index--;
            return tmp;
        }
    }
}