How do I access the last string in a list of command line options passed in via main(String[] args)?

Question

I'm building a Java application that takes a varying number of command line options as input, with a file name consistently the last item. When I specify the argument index in the second line below (e.g. args[2], everything does of course work correctly when I know the index ahead of time, but I'm having trouble coming up with the correct syntax for accessing the final item in a String[] when dealing with a file or even just a string as the input vs. an array of integers or something simpler for when that index number varies.

public static void main(String[] args) {

    String inFile = args.length-1;

Assuming `args` is not empty: `args[args.length - 1]`. – lexicore Apr 06 '18 at 14:54 — lexicore, Apr 06 '18 at 14:54

score 5 · Answer 1 · answered Apr 06 '18 at 14:54

5

You have to use

String inFile = args[args.length-1];
//array name    ^^^
//last index value   ^^^^^^^^^^^^^^

answered Apr 06 '18 at 14:54

Pavneet_Singh

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score 4 · Accepted Answer · answered Apr 06 '18 at 14:54

4

Try:

String inFile = args[args.length - 1];

answered Apr 06 '18 at 14:54

Tripp Kinetics

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Thanks, that worked. I realize this is a simple question, but I hope this makes other people's searches easier as I wasn't able to find this otherwise. – MarkCoder Apr 06 '18 at 14:56
My pleasure. Please accept and upvote my answer. – Tripp Kinetics Apr 06 '18 at 14:57

score 3 · Answer 3 · answered Apr 06 '18 at 14:58

3

If you are often needing this functionality you can encapsulate it into a method:

public static <T> T last(T[] them) {
    return them != null && them.length > 0 ? them[them.length - 1] : null;
}

public void test(String[] args) throws Exception {
    String fileName = last(args);
}

answered Apr 06 '18 at 14:58

OldCurmudgeon

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Fine but note that the null check is dead code as `String[] args` cannot be null in a main() method. – davidxxx Apr 06 '18 at 15:03
1

`null` can be an element in the array, so it shouldn't be returned as the "error" value. Better to throw `NullPointerException` if `them` is `null`, and `NoSuchElementException` if it is empty. – Andy Turner Apr 06 '18 at 15:05

How do I access the last string in a list of command line options passed in via main(String[] args)?

3 Answers3