// FIFO Queue implemented as circular array.
//  end field points after last element. Thus end==start for empty array.

public class CircularArray<T> {
    private T[] elements;
    int start;
    int end;

    public CircularArray(T[] elts) {
        elements = elts;
        start = 0;
        end = 0;
       }

    public boolean empty() { return end==start; }

    public boolean full() {
       return (((start==0) && end==elements.length-1) || end == start-1); }

    public void add(T x) {
        if (!full()) {
          elements[end] = x;
          end++;
          if (end==elements.length) end=0;
          }
     }

     public T first() { return elements[start]; }

     public T pop() {
         if (!empty()) {
            T x = elements[start];
            start = start+1;
            if (start==elements.length) start=0;
            return x;
          }
         else return null;
      }

     public String toString() {
        String S = "[";
        for (int i = start; i!=end; ) {
          S = S + elements[i].toString() + " ";
          i++;
          if (i==elements.length) i=0;
         }
        return S+"]";
      }

  public static void main(String[] args) {
      CircularArray<Integer> Q = new CircularArray<Integer>(new Integer[5]);
      Q.add(4);
      Q.add(14);
      Q.add(23);
      Q.pop();
      Q.add(28);
      Q.add(34);
      Q.pop();
      System.out.println(Q.toString());
 }
}