code: public ElementType get() {
          if (empty()) throw new IllegalArgumentException("Empty queue");
  
          ElementType x = (ElementType) elements[getIdx];
          getIdx = (getIdx + 1) % elements.length;
          size--;
          return x;
      }
docs: Removes the 'first' element.
  @return first element in the queue
  @throws IllegalArgumentException if empty