Implement a queue with max API

EPI Solution:
https://github.com/epibook/epibook.github.io/blob/master/solutions/java/src/main/java/com/epi/QueueWithMaxUsingDeque.java

  public static class Queue<T extends Comparable<T>> {
    private LinkedList<T> q = new LinkedList<>();
    private LinkedList<T> d = new LinkedList<>();

    public void enqueue(T x) {
      q.addFirst(x);
      while (!d.isEmpty() && d.getLast().compareTo(x) < 0) {
        d.removeLast();
      }
      d.addLast(x);
    }

    public T dequeue() {
      if (!q.isEmpty()) {
        T ret = q.removeLast();
        if (ret.equals(d.getFirst())) {
          d.removeFirst();
        }
        return ret;
      }
      throw new RuntimeException("empty queue");
    }

    public T max() {
      if (!d.isEmpty()) {
        return d.getFirst();
      }
      throw new RuntimeException("empty queue");
    }
    public T head() {
      return q.getLast();
    }
  }

Compute the maximum of a sliding window SlidingWindow.java

https://github.com/epibook/epibook.github.io/blob/master/solutions/java/src/main/java/com/epi/SlidingWindow.java

  public static class TrafficElement implements Comparable<TrafficElement> {

    private final int time, volume;

    public TrafficElement(int time, int volume) {

      this.time = time;

      this.volume = volume;

    }

    public int getTime() {

      return time;

    }

    public int getVolume() {

      return volume;

    }

    @Override

    public int compareTo(TrafficElement o) {

      int result = volume - o.getVolume();

      return result != 0 ? result : time - o.getTime();

    }

    @Override

    public boolean equals(Object o) {

      if (this == o) {

        return true;

      }

      if (o == null || getClass() != o.getClass()) {

        return false;

      }

      return compareTo((TrafficElement) o) == 0;

    }

  }

  public static void trafficVolumes(List<TrafficElement> A, int w) {

    Queue<TrafficElement> Q = new Queue<>();

    for (int i = 0; i < A.size(); i++) {

      Q.enqueue(A.get(i));

      while (A.get(i).getTime() - Q.head().getTime() > w) {

        Q.dequeue();

      }

      System.out.println("Max after inserting " + i + " is "

          + Q.max().getVolume());

    }

  }