Matt1776 Matt1776 - 1 year ago 103
Java Question

Using Apache Commons CLI to detect absence of command line arguments/options

I am currently using the library

Apache Commons CLI 1.3.1
to parse command line arguments and control the flow of execution in an executable jar. So far everything has been pretty straightforward and the documentation and example usage pages have been relatively thorough and helpful.

However, I am still unclear about how to use this library to detect the absence of any arguments or options. I would like to detect this condition and then print a usage/help statement. I have gotten around this by simply checking the length of the argument array, but I would like to know if the library has a way of detecting this condition without checking for the presence of every option.

Here is my code with the work-around left in:

public static void main(String[] args)
// create Options object
Options options = new Options();

// add t option
options.addOption("t", false, "display current time");
options.addOption("help", false, "print this message");

CommandLineParser parser = new DefaultParser();
CommandLine cmd = parser.parse(options, args);

if(cmd.hasOption("t")) {
log.debug("Received option t");
// Do something

if (args.length <= 0 || cmd.hasOption("help"))
// automatically generate the help statement
HelpFormatter formatter = new HelpFormatter();
formatter.printHelp( "java -jar Client.jar <option> <arguments>", options);
catch (Exception ex)

Answer Source

I think you're looking for the getArgList or the getArgs method. From the documentation:

Retrieve any left-over non-recognized options and arguments

So instead of this:

   if (args.length <= 0 || cmd.hasOption("help"))

Use like this:

   if (cmd.getArgs.length == 0 || cmd.hasOption("help"))
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