right = right.rotateRight();
          }
          return rotateLeft();
        case 2:
          // requireNonNull is safe because left must exist in order to get a positive factor.
          requireNonNull(left);
          if (left.balanceFactor() < 0) {
            left = left.rotateLeft();
          }
          return rotateRight();
        default:
          recomputeHeight();