Parsing arguments to a Java command line program

Question

What if I wanted to parse this:

java MyProgram -r opt1 -S opt2 arg1 arg2 arg3 arg4 --test -A opt3

And the result I want in my program is:

Answer 1

I like this one. Simple, and you can have more than one parameter for each argument:

final Map> params = new HashMap<>();

List options = null;
for (int i = 0; i < args.length; i++) {
    final String a = args[i];

    if (a.charAt(0) == '-') {
        if (a.length() < 2) {
            System.err.println("Error at argument " + a);
            return;
        }

        options = new ArrayList<>();
        params.put(a.substring(1), options);
    }
    else if (options != null) {
        options.add(a);
    }
    else {
        System.err.println("Illegal parameter usage");
        return;
    }
}

For example:

-arg1 1 2 --arg2 3 4

System.out.print(params.get("arg1").get(0)); // 1
System.out.print(params.get("arg1").get(1)); // 2
System.out.print(params.get("-arg2").get(0)); // 3
System.out.print(params.get("-arg2").get(1)); // 4