Ignore case for 'contains' for a string in Java

Question

Consider:

public static void main(String[] args) {

    String s = "AbcD";

    System.out.println(s.contains("ABCD"));
    System.out.println(s.contains("AbcD"));
}

Output:

false
true

I need the result to be true in both cases regardless of the case. Is it possible?

See http://stackoverflow.com/questions/14018478/string-contains-ignore-case — devnull, May 17 '13 at 08:43

score 44 · Accepted Answer · answered May 17 '13 at 08:35

44

You need to convert both the strings to the same case before using contains

s.toLowerCase().contains("ABCD".toLowerCase());

answered May 17 '13 at 08:35

sanbhat

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This won't necessarily work, since case convertion is locale specific. `"i".toLowerCase().contains("I".toLowerCase())` may e.g. return false. – jarnbjo May 17 '13 at 08:50
1

@jarnbjo I tested it in my location(middle east), US and English but that's not true. what location do you mean? – David Aug 29 '16 at 09:55
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@David Any locale with deviating upper/lower-case rules won't work as expected. For Turkish, `"I".toLowerCase();` will e.g. return `"ı"` and not `"i"`. – jarnbjo Aug 29 '16 at 10:15

score 30 · Answer 2 · edited May 17 '13 at 09:35

30

You could use org.apache.commons.lang3.StringUtils.containsIgnoreCase(String, String)

StringUtils.containsIgnoreCase(s, "ABCD") returns true

Apache documentation here

edited May 17 '13 at 09:35

Subhrajyoti Majumder

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answered May 17 '13 at 08:35

David

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I think this has the best answer out of all. Much more convenient. @PSR, I think you should mark this as answer if this really helps. – Michael 'Maik' Ardan May 17 '13 at 08:46

zakinster · Answer 3 · 2019-03-26T14:25:39.117

5

Not that it would be particularly efficient but you could use a Pattern matcher to make a case-insensitive match:

Pattern pattern = Pattern.compile(Pattern.quote(s), Pattern.CASE_INSENSITIVE);
pattern.matcher("ABCD").find();
pattern.matcher("AbcD").find();

Also note that it won't magically solve the locale issue but it will handle it differently than toLowercase(Locale), with the conjunction of the Pattern.UNICODE_CASE flag, it may be able to handle all locales at once.

edited Mar 26 '19 at 14:25

answered May 17 '13 at 08:36

zakinster

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A bit inefficient to use RegEx for this :) – Philip Helger May 17 '13 at 08:36
@phloc The problem of using `toLowerCase()` is that the result depends on the current locale. – zakinster May 17 '13 at 08:40
That's why I suggested toLowercase(Locale.US) - or whatever locale you want. – Philip Helger May 17 '13 at 08:42
what if your string contains special chars for example s= "example\". In this case this pattern matcher will fail. – Mohit Bhagat Sep 28 '20 at 11:32

score 3 · Answer 4 · edited May 17 '13 at 08:36

3

Using "toLowercase" helps:

System.out.println(s.toLowercase(Locale.US).contains("ABCD".toLowercase (Locale.US)));

(of course you could also use toUppercase instead)

edited May 17 '13 at 08:36

PSR

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answered May 17 '13 at 08:36

Philip Helger

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score 2 · Answer 5 · edited Oct 30 '15 at 17:20

2

You can do this with toLowerCase. Something like this:

s.toLowerCase().contains("aBcd".toLowerCase());

edited Oct 30 '15 at 17:20

Peter Mortensen

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answered May 17 '13 at 08:57

Hugo Pedrosa

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score 1 · Answer 6 · edited Oct 30 '15 at 17:21

1

Try the following. It will return 0 if the string matched...

System.out.println(s.compareToIgnoreCase("aBcD"));

It will work fine.

edited Oct 30 '15 at 17:21

Peter Mortensen

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answered May 17 '13 at 09:05

KhAn SaAb

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contains and compare are two different things – Bu Saeed Nov 25 '21 at 08:58
@BuSaeed- obviously. – KhAn SaAb Nov 25 '21 at 09:25

Ignore case for 'contains' for a string in Java

6 Answers6