code: public RepairDigramRecord dequeue() {
      if (null != this.head) {
        RepairDigramRecord el = this.head.payload;
        this.head = this.head.next;
        if (null != this.head) {
          this.head.prev = null;
        }
        this.elements.remove(el.str);
        // System.out.println(this);
        return el;
      }
      return null;
    }
docs: Returns the most frequently seen element -- the head of the queue.
  
  @return the digram record from the top of the queue or a null.