Java regex case insensitivity not working

Question

I'm trying to remove some words in a string using regex using below program. Its removing properly but its considering only case sensitive. How to make it as case insensitive. I kept (?1) in replaceAll method but it didn't work.

package com.test.java;

public class RemoveWords {

    public static void main(String args[])
    {

        // assign some words to string

        String sample ="what Is the latest news today in Europe? is there any thing special or everything is common.";

            System.out.print(sample.replaceAll("( is | the |in | any )(?i)"," "));
    }
}

OUTPUT:

what Is latest news today  Europe? there thing special or everything common.

Positive Navid · Accepted Answer · 2016-12-01 21:54:57Z

33

You need to place the (?i) before the part of the pattern that you want to make case insensitive:

System.out.print(sample.replaceAll("(?i)\\b(?:is|the|in|any)\\b"," "));
                                    ^^^^

See it

I've replaced spaces around the keywords to be removed with word boundary (\\b). The problem comes because there may be two keywords one after another separated by just one space.

If you want to delete the keywords only if they are surrounded by space, then you can use positive lookahead and lookbehind as:

(?i)(?<= )(is|the|in|any)(?= )

See it

edited Dec 1, 2016 at 21:54

Positive Navid

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answered Jan 27, 2011 at 6:59

codaddict

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8 Comments

user467871 Over a year ago

"the" exists in the output. it didn't replace with " " and it doesn't remove "IS" see it ideone.com/HMxLr

JavaGeek Over a year ago

Correct. Why it's not replacing "the" with " " . Any problem with the regex

Jon Skeet Over a year ago

@codaddict: Note that this leaves multiple spaces in a row, which is possibly not ideal but may be tricky to avoid.

user467871 Over a year ago

@codaddict works but I don't understand anything from this regex. Anyway, I revert my -1

codaddict Over a year ago

@Jon: You are right. But adding a .replaceAll(" +"," ") will solve that. Doing all this in a single regex will be tricky.

|

Chandu · Accepted Answer · 2011-01-27 06:59:03Z

4

I don't think you can specify case insensitive with the quick replace. Try a pattern instead. i.e:

package com.test.java;

public class RemoveWords {

public static void main(String args[]) {
  // assaign some words to string
  String sample ="what Is the latest news today in Europe? is there any thing special or everything is common.";
  String regex = "( is | the |in | any )"
  System.out.print
  (
    Pattern.compile(regex, Pattern.CASE_INSENSITIVE).matcher(sample).replaceAll("")
  );
 }
}

answered Jan 27, 2011 at 6:59

Chandu

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2 Comments

Joachim Sauer Over a year ago

Sorry for the downvote, but as @codaddicts answer shows, you can use those flags in String.replaceAll().

Chandu Over a year ago

@Joachim: No worries. I upvoted @Codaddicts answer since I got to know how to use flags in String.replaceAll

user467871 · Accepted Answer · 2011-01-27 06:50:43Z

1

change is to [iI][sS]

sample.replaceAll("( [iI][sS] ...

answered Jan 27, 2011 at 6:50

user467871

1 Comment

JavaGeek Over a year ago

It works but lengthy process where we need to put every character. Is there any better way

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