check if a string contains characters java code example

Example 1: how to check if a char is a letter java

Character.isDigit(string.charAt(index)) //(JavaDoc) will return true if it's a digit
Character.isLetter(string.charAt(index)) //(JavaDoc) will return true if it's a letter

Example 2: how to check if a string contains a character

public static boolean containsIgnoreCase(String str, char c) {
        str = str.toLowerCase();

        for (int i = 0; i < str.length(); i++) {
            if (str.charAt(i) == Character.toLowerCase(c)) {
                return true;
            }
        }
        
        return false;
    }