private boolean containsNoteAtPosition(List<NotePos> notePositions, int notePosition) {
   for (NotePos notePos : notePositions) {
     if (notePos.getPosition() == notePosition) {
       return true;
     }
   }
   return false;
 }
 private void shiftNote(NotePos note, List<NotePos> mergedNotePositions, int index) {
   NotePos prevOrNextNote = mergedNotePositions.get(index);
   if (prevOrNextNote.getVoice() != note.getVoice()) {
     int prevOrNextPosition = prevOrNextNote.getPosition();
     int notePosition = note.getPosition();
     int length = Math.abs(notePosition - prevOrNextPosition);
     if (length > MIN_LENGTH && (length % 2) == 0) { // divisable by 2
       note.setPosition(notePosition + (length / 2));
       System.out.println("shift");
     } else {
       note.setPosition(prevOrNextPosition);
     }
   }
 }
  /**
   * Perform the mutation operation
   *
   * @param probability Mutation probability
   * @param solution The solution to mutate
   * @throws JMException
   */
  public void doMutation(double probability, Solution solution) throws JMException {
    if (PseudoRandom.randDouble() < probability) {
      List<Partition> partitions =
          ((MusicVariableAtonal) solution.getDecisionVariables()[0]).getPartitions();
      int s = partitions.size() - 1;
      int melodyIndex = PseudoRandom.randInt(0, s);
      Partition partition = partitions.get(melodyIndex);
      List<NotePos> notePositions = partition.getNotes();
      int startPartition = partition.getPosition();
      int endPartition = startPartition + partition.getLength();
      if (!notePositions.isEmpty() && notePositions.size() > 1) {
        int position = PseudoRandom.randInt(0, notePositions.size() - 1);
        NotePos note = notePositions.get(position);
        int index = notePositions.indexOf(note);
        if (random.nextBoolean()) {
          if (index >= 1) {
            NotePos prevNote = notePositions.get(index - 1);
            if (prevNote.getVoice() != note.getVoice()) {
              //								int prevPosition = prevNote.getPosition();
              int notePosition = note.getPosition();
              if (!containsNoteAtPosition(notePositions, notePosition - MIN_LENGTH)
                  && startPartition <= notePosition - MIN_LENGTH) {
                note.setPosition(notePosition - MIN_LENGTH);
                System.out.println("Shifted");
              }
            }
          }

        } else {
          if (index < notePositions.size() - 1) {
            NotePos nextNote = notePositions.get(index + 1);
            if (nextNote.getVoice() != note.getVoice()) {
              //								int nextPosition = nextNote.getPosition();
              int notePosition = note.getPosition();
              if (!containsNoteAtPosition(notePositions, notePosition + MIN_LENGTH)
                  && notePosition + MIN_LENGTH <= endPartition) {
                note.setPosition(notePosition + MIN_LENGTH);
                System.out.println("Shifted");
              }
            }
          }
        }
      }
    }
  }