private Calculator createCalculator(CommandLine commandLine,
List<Alignment> alignmentList) {
String calculatorString = commandLine.getOptionValue('a');
if (calculatorString == null) {
throw new MissingParameterException("calculator");
}
List<String> calculatorStringList =
Arrays.asList(calculatorString.split(","));
return createCalculator(commandLine, alignmentList, calculatorStringList);
}