Find occurrences of characters in a Java String [duplicate]

Question

I would like to count the occurrences of a character in a string, suppose I have the string "aaaab", how would i count the amount of a's in it?

Answer 1

Guava's CharMatcher API is quite powerful and concise:

CharMatcher.is('a').countIn("aaaab"); //returns 4

Answer 2

String string = "aaab";
int count = string.length() - string.replaceAll("a", "").length();

instead of "a" use a regex like "[a-zA-Z]" to count all word characters