How to check if a String contains another String in a case insensitive manner in Java?

Question

Say I have two strings,

String s1 = "AbBaCca"; String s2 = "bac";

I want to perform a check returning that s2 is contained within s1. I can do this with:

return s1.contains(s2);

I am pretty sure that contains() is case sensitive, however I can't determine this for sure from reading the documentation. If it is then I suppose my best method would be something like:

return s1.toLowerCase().contains(s2.toLowerCase());

All this aside, is there another (possibly better) way to accomplish this without caring about case-sensitivity?

Answer 1

Yes, contains is case sensitive. Here is another way for case insensitive matching using java.util.regex.Pattern with the CASE_INSENSITIVE flag:

Pattern.compile(Pattern.quote(s2), Pattern.CASE_INSENSITIVE).matcher(s1).find();

You need to use Pattern.quote() on s2 if regex special characters.

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