Java mergesort exercise

package exercises;
public class MergeSort {
  private static void merge(int[] values, int leftStart, int midPoint,
      int rightEnd) {
    int intervalSize = rightEnd - leftStart;
    int[] mergeSpace = new int[intervalSize];
    int nowMerging = 0;
    int pointLeft = leftStart;
    int pointRight = midPoint;
    do {
      if (values[pointLeft] <= values[pointRight]) {
        mergeSpace[nowMerging] = values[pointLeft];
        pointLeft++;
      } else {
        mergeSpace[nowMerging] = values[pointRight];
        pointRight++;
      }
      nowMerging++;
    } while (pointLeft < midPoint && pointRight < rightEnd);
    int fillFromPoint = pointLeft < midPoint ? pointLeft : pointRight;
    System.arraycopy(values, fillFromPoint, mergeSpace, nowMerging,
        intervalSize - nowMerging);
    System.arraycopy(mergeSpace, 0, values, leftStart, intervalSize);
  }
  public static void mergeSort(int[] values) {
    mergeSort(values, 0, values.length);
  }
  private static void mergeSort(int[] values, int start, int end) {
    int intervalSize = end - start;
    if (intervalSize < 2) {
      return;
    }
    boolean isIntervalSizeEven = intervalSize % 2 == 0;
    int splittingAdjustment = isIntervalSizeEven ? 0 : 1;
    int halfSize = intervalSize / 2;
    int leftStart = start;
    int rightEnd = end;
    int midPoint = start + halfSize + splittingAdjustment;
    mergeSort(values, leftStart, midPoint);
    mergeSort(values, midPoint, rightEnd);
    merge(values, leftStart, midPoint, rightEnd);
  }
}