How to make a regular expression for given kind of String?

Question

How to write the regular expression for below kind of String such that I get response in below format ?

"abc, -xyz, lmn, qwe,-yui"

Basically I need to parse above string in List<String> as

abc, -xyz
lmn
qwe, -yui

Below code is working fine when there is exactly one space before hyphen(-) ex:

"abc, -xyz"

but not working when there is no or more than one space, ex:

"abc,  -xyz"

Regular expression I tried:

List<String> items = Arrays.stream(order.split("(?!, -),")).map(String::trim).map(String::toLowerCase).collect(Collectors.toList());

Please provide the code which parse with any number of spaces and also explain the logic for the same.

If you are parsing CSV data it might be easier to use some utility, as opposed to writing regular expressions for it. — npinti, Jul 03 '19 at 13:23
As every `,` you want to split on is preceded by a `"`, split on `",` and re-add the now missing `"` on every element but the last — roookeee, Jul 03 '19 at 13:23
As you can see, people start guessing about the nature of the problem you are trying to solve here. Thus: consider telling us *why* you want to split such strings, and where they "come from". — GhostCat, Jul 03 '19 at 13:27
If your issue is the white space, then you may change your regex to `"(?!,\\s+-),"` — Luiggi Mendoza, Jul 03 '19 at 13:41
@WiktorStribiżew It would be great if you can explain the code in short. Thanks — aarish_codev, Jul 05 '19 at 05:39
@Toto How can this be a duplicate to what you have marked ? Please explain. — aarish_codev, Jul 05 '19 at 05:40
I added another dupe, your answer is [here](https://stackoverflow.com/a/4972133/3832970). `(?!,\s*-),` matches any comma that is not followed with any 0 or more whitespaces and a `-`. It is equal to `,(?!\s*-)`. — Wiktor Stribiżew, Jul 05 '19 at 07:29

score 0 · Answer 1 · answered Jul 03 '19 at 20:03

Instead of splitting your string you can actually find all results using "(.+?)". This finds all string between ". Here is the full example:

String input = "\"abc, -xyz\", \"lmn\", \"qwe,-yui\"";
Pattern pattern = Pattern.compile("\"(?<item>.+?)\"");
Matcher matcher = pattern.matcher(input);
List<String> items = new ArrayList<>();
while (matcher.find()) {
    items.add(matcher.group("item"));
}
items.forEach(System.out::println);

The result will be this:

abc, -xyz
lmn
qwe,-yui

You also can use .trim(),toLowercase() before adding an item to the list if you need that.

How to make a regular expression for given kind of String?

1 Answers1