code: @Override
    public int compareTo(Object other) {
      if (other == null) {
        return -1;
      }
      TaskKey otherKey = (TaskKey) other;
      return new CompareToBuilder().appendSuper(super.compareTo(otherKey))
          .append(this.taskId, otherKey.getTaskId())
          .toComparison();
    }
docs: Compares two TaskKey objects on the basis of their taskId
  
  @param other
  @return 0 if the taskIds are equal,
  1 if this taskId is greater than other taskId,
  -1 if this taskId is less than other taskId