How to define an option to accept only one value, but allow to use it multiple times?

I can’t figure out how to define an option which does accept only one value but can be specified multiple times. To be exact:

application -o value1 -o value2 parameter1 parameter2

When defined without arity, parameter1 and parameter2 are added to o. I tried this:

@Option(names = { "-o", "--open" }, arity = "1")
private List<String> files = null;

But that disallows multiple usage of -o.

How can I define this?

[remkop]

If only one value is allowed, why not make it a String instead of a List?

@Option(names = { "-o", "--open" })
private String files = null;

Now, if the option is specified multiple times, picocli will throw a OverwrittenOptionException by default, but you can make it lenient by calling CommandLine.setOverwrittenOptionsAllowed(true) before parsing the input.

This way the last option value specified on the command line is preserved.

See also http://picocli.info/#_too_many_values

[RobertZenz]

I’ve just build the latest master (39f1944) and it works, thank you very very much for the fast response.