Matching "camelCase" to a regular expression in java

Question

String camelCasePattern = "([a-z][A-Z0-9]+)+";

boolean val = "camelCase".matches(camelCasePattern);
System.out.println(val);

The above prints false. I'm trying to match a camelCase pattern starting with lower case letter. I have tried to tweak it a bit, without no luck though. Is the pattern wrong for camelCase?

Answer 1

I would go with:

String camelCasePattern = "([a-z]+[A-Z]+\\w+)+"; // 3rd edit, getting better
System.out.println("camelCaseCaseCCase5".matches(camelCasePattern));

Output

true

Your current Pattern is matching one lowercase followed by as many uppercase/digit, many times over, which is why it returns false.

Answer 2

The best way to match your test case is:

String camelCasePattern = "^[a-z]+([A-Z][a-z0-9]+)+";

This will ensure it starts with a lowecase, and then has a repeating pattern of one capital letter, followed by some lowercase characters

Matches camelCaseTest but not camelCaseDOneWrong