Java string replaceAll regex

Question

Hi I want to remove certain words from a long string, there problem is that some words end with "s" and some start with a capital, basically I want to turn:

"Hello cat Cats cats Dog dogs dog fox foxs Foxs"

into:

"Hello"

at the moment I have this code but I want to improve on it, thanks in advance:

                    .replace("foxs", "")
                    .replace("Fox", "")
                    .replace("Dogs", "")
                    .replace("Cats", "")
                    .replace("dog", "")
                    .replace("cat", "")

Use case insensitive flag (?i) and (?i)\s(?:fox|dog|cat)s? — Srdjan M.
– Srdjan M., Commented Feb 28, 2018 at 15:50

Tim Biegeleisen · Accepted Answer · 2018-02-28 15:54:06Z

7

Try this:

String input = "Hello cat Cats cats Dog dogs dog fox foxs Foxs";
input = input.replaceAll("(?i)\\s*(?:fox|dog|cat)s?", "");

Demo

edited Feb 28, 2018 at 15:54

answered Feb 28, 2018 at 15:51

Tim Biegeleisen

526k32 gold badges323 silver badges399 bronze badges

Sign up to request clarification or add additional context in comments.

3 Comments

Pshemo Over a year ago

I would remove one \\s*, otherwise foo cat bar would become foobar instead of (I am guessing preferred) foo bar.

Tim Biegeleisen Over a year ago

@Pshemo Yes you're right ... the commenter S Jovan left a brilliant and flawless pattern about 30 seconds before I posted.

Pshemo Over a year ago

Yes, writing answer containing fully executable code takes more time than writing only solution :)

King Midas · Accepted Answer · 2018-02-28 16:38:09Z

3

Maybe you can try to match everything except the word Hello. Something like:

string.replaceAll("(?!Hello)\\b\\S+", "");

You can test it in this link.

The idea is to perform a negative lookahead for Hello word, and get any other word present.

edited Feb 28, 2018 at 16:38

answered Feb 28, 2018 at 15:54

King Midas

1,7494 gold badges38 silver badges60 bronze badges

2 Comments

Pshemo Over a year ago

One of \\b is redundant.

King Midas Over a year ago

yes, you are right. I edit the answer and remove one of them.

Wes · Accepted Answer · 2018-02-28 16:00:00Z

1

So you could pre-compile a list of the words you want and make it case insensitive something like:

    String str = "Hello cat Cats cats Dog dogs dog fox foxs Foxs";
    Pattern p = Pattern.compile("fox[s]?|dog[s]?|cat[s]?", Pattern.CASE_INSENSITIVE);
    Matcher m = p.matcher(str);
    String result = m.replaceAll("");
    System.out.println(result);

[s]? handles if there is a plural form, where the ? character will match 0 or 1

answered Feb 28, 2018 at 16:00

Wes

212 bronze badges

3 Comments

Wes Over a year ago

So you don't have to have it inside of there. it was more so in case you wanted to match a set of characters or range of characters at the end [0-9] or [s|es]. I agree this was not necessarily clear. So it could be just: Pattern.compile("foxs?|dogs?|cats?", Pattern.CASE_INSENSITIVE);

Pshemo Over a year ago

It is good you realise that s? and [s]? will work same way (IMO adding [ ] makes it harder to understand - especially for someone new to regex - but that is matter of personal preference). Aside from that "or [s|es]" doesn't look like proper example (or you are misunderstanding it) since [...] can match only single character from set of characters defined in [...]. So [s|es] can match only s or | or e (putting s second time doesn't change anything here).

Wes Over a year ago

Valid points. In my second case it should have been (s|es) and I do agree that it does make it harder to understand, always room for improvement

Tamas Rev · Accepted Answer · 2018-02-28 15:54:34Z

You can generate patterns that match all combinations for a word. I.e. for dog you need the pattern [Dd]ogs?:

[Dd] is a character class that matches both cases
s? matches zero or one s
the rest of the word will be case sensitive. I.e. dOGS will not be a match.

This is how you can put it together:

public static void main(String[] args) {
    // it's easy to add any other word
    String original = "Hello cat Cats cats Dog dogs dog fox foxs Foxs";
    String[] words = {"fox", "dog", "cat"};
    String tmp = original;
    for (String word : words) {
        String firstChar = word.substring(0, 1);
        String firstCharClass = "[" + firstChar.toUpperCase() + firstChar.toLowerCase() + "]";
        String patternSrc = firstCharClass + word.substring(1) + "s?"; // [Ww]ords?
        tmp = tmp.replaceAll(patternSrc, "");
    }
    tmp = tmp.trim(); // to remove unnecessary spaces 
    System.out.println(tmp);
}

Collectives™ on Stack Overflow

Java string replaceAll regex

4 Answers 4

Demo

3 Comments

2 Comments

3 Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

4 Answers 4

3 Comments

2 Comments

3 Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related