code: @Override
      public Quaterniond normalize() {
          final double length = length();
          if (Math.abs(length) < GenericMath.DBL_EPSILON) {
              throw new ArithmeticException("Cannot normalize the zero quaternion");
          }
          return new Quaterniond(x / length, y / length, z / length, w / length);
      }
docs: Normalizes this quaternion.
  
  @return A new quaternion of unit length