Simple way to count character occurrences in a string [duplicate]

public int countChar(String str, char c)
{
    int count = 0;

    for(int i=0; i < str.length(); i++)
    {    if(str.charAt(i) == c)
            count++;
    }

    return count;
}

This is definitely the fastest way. Regexes are much much slower here, and possible harder to understand.

Functional style (Java 8, just for fun):

str.chars().filter(num -> num == '$').count()

Not optimal, but simple way to count occurrences:

String s = "...";
int counter = s.split("\\$", -1).length - 1;

Note:

• Dollar sign is a special Regular Expression symbol, so it must be escaped with a backslash.
• A backslash is a special symbol for escape characters such as newlines, so it must be escaped with a backslash.
• The second argument of split prevents empty trailing strings from being removed.

You can use Apache Commons' StringUtils.countMatches(String string, String subStringToCount).