code: public boolean validate(int allowedFlags, boolean allowPrecision) {
      // The default instance is always valid (commonest case).
      if (isDefault()) {
        return true;
      }
      // Check if our flags are a subset of the allowed flags.
      if ((flags & ~allowedFlags) != 0) {
        return false;
      }
      // Check we only have precision specified when it is allowed.
      if (!allowPrecision && precision != UNSET) {
        return false;
      }
      return checkFlagConsistency(flags, getWidth() != UNSET);
    }
docs: Validates these options according to the allowed criteria and checks for inconsistencies in
  flag values.
  <p>
  Note that there is not requirement for options used internally in custom message parsers to be
  validated, but any format options passed through the {@code ParameterVisitor} interface must
  be valid with respect to the associated {@link FormatChar} instance.
  
  @param allowedFlags a bit mask specifying a subset of the printf flags that are allowed for
  these options.
  @param allowPrecision true if these options are allowed to have a precision value specified.
  @return true if these options are valid given the specified constraints.