code: public static final NumericalValueRange create (final int min, final int max) {
          if (min > max) return null;
          return new NumericalValueRange(min, max);
      }
docs: The build method for creating {@link NumericalValueRange} objects. The specified <i>min</i> and <i>max</i>
  parameters are going to be used for initializing the {@link #min} and {@link #max} variables of the new
  {@link NumericalValueRange}. Since this only makes sense if <i>min</i> &le; <i>max</i>, <code>null</code> will be
  returned if this requirement is violated.
  
  @param min the lower bound
  @param max the upper bound
  @return a {@link NumericalValueRange} representing the specified interval or <code>null</code>