check number of a given character occurence in a String

Question

I want to write a simple class to process Strings (may be very long strings up to 1mil characters in it). String will basically consists of two characters \"a\" and \"b\" that

Answer 1

If you want you can use a third party library like StringUtils. It has a method countMatches which will do the work.

StringUtils.countMatches("abba", "a")   = 2
StringUtils.countMatches("abba", "ab")  = 1