code: public final Object getValue(int varNum) {
      int index = getValueIndex(varNum);
      if (index < 0) {
        return null;
      } else {
        return values[index];
      }
    }
docs: Gets the value assigned to variable {@code varNum}. Returns {@code null} if
  {@code varNum} does not have a value.
  
  @param varNum
  @return