CODEWITHSUNDEEP
javaregex
BigMikeW
BigMikeW

Reputation: 831

Regex to parse list items except blacklisted term

I'm trying to construct a single regex that will match a list only if it contains a specific item in the list and return all other items in the list except the one that matched.

E.g.: With this list I want to match on fruit but only return apple, orange and banana:

apple, fruit, orange, banana

I'm currently trying variations of this:

\b(?:fruit)\b|[^,\s][^\,]*[^,\s]*

This is a Java regex implementation but assume that I have no access to the code that's running the actual regex.

Upvotes: 2

Views: 123

Answers (3)

Allan
Allan

Reputation: 12448

enter image description hereI have prepared the following regex that works fine for any position of your element in your list.

(.*)apple(,\s)(.*)|(.*)(,\s)apple(.*)

then you have to use the following backreference to construct your result list

$1$3$4$6

of course each time you use the regex you will have to change "apple" by the element that must be removed from the list, for this purpose create a variable that stores the element that must be removed and construct the regex dynamically by concatenating the following elements:

"(.*)" + elementToBeRemoved + "(,\s)(.*)|(.*)(,\s)" + elementToBeRemoved + "(.*)"

I have tried with banana, apple, fruit and orange and it works perfectly!!!

Upvotes: 0

CAustin
CAustin

Reputation: 4614

Unless I'm missing something, you should be able to simply match (.*)\bfruit\b(?:, )?(.*) and replace with \1\2

Upvotes: 1

Tim Biegeleisen
Tim Biegeleisen

Reputation: 521997

Regex may not be the best tool here, but loading your items into a list may work better. In the code snippet below, I convert your CSV list of items/fruits into a formal list. With that list in hand, it is easy to determine if a certain item be present. If fruit is found, then we can return the list minus that item, otherwise null is returned.

public List<String> getItems(String input, String match) {
    String[] array = input.split(",\\s*");
    List<String> list = Arrays.asList(array);
    if (list.contains(match)) {
        return list.remove(match);
    }
    else {
        return null;
    }
}

String fruits = "apple, fruit, orange, banana";
List<String> result = getItems(fruits, "fruit");

Upvotes: 1

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