code: public static String capitalize(String value) {
  
      Assert.hasText(value, "Value [%s] is required", value);
  
      String firstCharacter = String.valueOf(value.charAt(0));
  
      return firstCharacter.toUpperCase().concat(value.substring(1));
    }
docs: Capitalizes the first {@link Character letter} for the {@link String}.
  
  @param value {@link String} to capitalize.
  @return the given {@link String} with the first {@link Character letter} capitalized.
  @throws IllegalArgumentException if the {@link String value} does not contain any {@link String text}.