public static void main(String[] args) {

        //System.out.println(isValid("([])"));

        //testQueue();

        testStack();

    }

    public static void testDeque() {

        //双端队列

        Deque<Integer> deque = new ArrayDeque<>();

        Deque<Integer> deque1 = new LinkedList<>();

        //入队

        deque1.addFirst(1);

        deque1.addLast(2);

        deque1.offerFirst(3);

        deque1.offerLast(4);

        System.out.println(deque1.peekFirst());

        System.out.println(deque1.peekLast());

        //出队

        System.out.println(deque1.removeFirst());

        System.out.println(deque1.removeLast());

        System.out.println(deque1.pollFirst());

        System.out.println(deque1.pollLast());

    }

    public static void testQueue() {

        Queue<Integer> queue = new LinkedList<>();

        queue.offer(1);

        queue.offer(2);

        queue.add(3);

        System.out.println(queue.peek());

        System.out.println(queue.poll());

        System.out.println(queue.peek());

        System.out.println(queue.remove());

        System.out.println(queue.peek());

    }

    public static void testStack() {

        Stack<Integer> stack = new Stack<>();

        stack.add(1);

        stack.push(2);

        stack.push(3);

        System.out.println(stack.peek());

        System.out.println(stack.pop());

        System.out.println(stack.peek());

        System.out.println(stack.remove(stack.size() - 1));

        System.out.println(stack.peek());

    }