code: public AxisAngle4f rotate(float ang) {
          angle += ang;
          angle = (float) ((angle < 0.0 ? Math.PI + Math.PI + angle % (Math.PI + Math.PI) : angle) % (Math.PI + Math.PI));
          return this;
      }
docs: Increase the rotation angle by the given amount.
  <p>
  This method also takes care of wrapping around.
  
  @param ang
  the angle increase
  @return this