message: Use "charAt" instead of "toCharArray" because it is more efficient.
diff: @@ -66,7 +66,8 @@ final class JwtFormat {
  }
  static byte[] strictUrlSafeDecode(String encodedData) throws JwtInvalidException {
  - for (char c : encodedData.toCharArray()) {
  + for (int i = 0; i < encodedData.length(); i++) {
  + char c = encodedData.charAt(i);
  if (!isValidUrlsafeBase64Char(c)) {
  throw new JwtInvalidException("invalid encoding");
  }
  @@ -226,7 +227,8 @@ final class JwtFormat {
  }
  static void validateASCII(String data) throws JwtInvalidException {
  - for (char c : data.toCharArray()) {
  + for (int i = 0; i < data.length(); i++) {
  + char c = data.charAt(i);
  if ((c & 0x80) > 0) {
  throw new JwtInvalidException("Non ascii character");
  }
  