code: @Override
    public int compareTo(TaskDetails otherTask) {
      if (otherTask == null) {
        return -1;
      }
  
      return new CompareToBuilder().append(this.taskKey, otherTask.getTaskKey())
          .toComparison();
    }
docs: Compares two TaskDetails objects on the basis of their TaskKey
  
  @param other
  @return 0 if this TaskKey is equal to the other TaskKey,
  1 if this TaskKey greater than other TaskKey,
  -1 if this TaskKey is less than other TaskKey