Question

I need help coming up with a regular expression to match if a string has more than one occurrence of character. I already validated the length of the two strings and they will always be equal. Heres what i mean, for example. The string “aab” and “abb”. These two should match the regular expression because they have repeating characters, the “aa” in the first string and the “bb” in the second.

Answer 1

Since you say “aba”-style repetition doesn’t count, back-references should make this simple:

(.)\1+

Would find sequences of characters. Try it out:

java.util.regex.Pattern.compile("(.)\\1+").matcher("b").find(); // false
java.util.regex.Pattern.compile("(.)\\1+").matcher("bbb").find(); // true