Implement stack and queue APIs using heaps - EPI

Implement stack and queue APIs using heaps

StackQueueUsingHeapTemplate.java
  private static class Compare<T> implements Comparator<Pair<Integer, T>> {
    @Override
    public int compare(Pair<Integer, T> o1, Pair<Integer, T> o2) {
      return o2.getFirst().compareTo(o1.getFirst());
    }
  }

  public static class Stack<T> {
    private int order = 0;
    private PriorityQueue<Pair<Integer, T>> H = new PriorityQueue<>(
        11, new Compare<T>());

    public void push(T x) {
      H.add(new Pair<Integer, T>(order++, x));
    }

    public T pop() {
      return H.remove().getSecond();
    }

    public T peek() {
      return H.peek().getSecond();
    }
  }

  public static class Queue<T> {
    private int order = 0;
    private PriorityQueue<Pair<Integer, T>> H = new PriorityQueue<>(
        11, new Compare<T>());

    public void enqueue(T x) {
      H.add(new Pair<Integer, T>(order--, x));
    }

    public T dequeue() {
      return H.remove().getSecond();
    }

    public T head() {
      return H.peek().getSecond();
    }
  }