code: public static String toLowerCamelCase(String text, char separator) {
          char[] chars = text.toCharArray();
          int base = 0, top = 0;
  
          do {
              while (top < chars.length && chars[top] != separator) {
                  chars[base++] = Character.toLowerCase(chars[top++]);
              }
              while (top < chars.length && chars[top] == separator) {
                  ++top;
              }
              if (top < chars.length) {
                  chars[base++] = Character.toUpperCase(chars[top++]);
              }
          } while (top < chars.length);
  
          return new String(chars, 0, base);
      }
docs: Converts a word sequence into a single camel-case word that starts with a lowercase letter.
  
  @param text - a word sequence with the given separator
  @param separator - a word separator
  @return a single camel-case word