@NonNull static String toHexString(@Nullable final byte[] src){
  if (src == null) {
    return "null";
  }
  final StringBuilder buffer=new StringBuilder();
  buffer.append("[");
  boolean needComma=false;
  for (  final byte srcByte : src) {
    if (needComma) {
      buffer.append(", ");
    }
    buffer.append(String.format("%02x",srcByte & 0xff));
    needComma=true;
  }
  buffer.append("]");
  return buffer.toString();
}

@ NonNull static String toHexString ( @ Nullable final byte [ ] src ) { if ( src == null ) { return "null" ; } final StringBuilder buffer = new StringBuilder ( ) ; buffer . append ( "[" ) ; boolean needComma = false ; for ( final byte srcByte : src ) { if ( needComma ) { buffer . append ( ", " ) ; } buffer . append ( String . format ( "%02x" , srcByte & 0xff ) ) ; needComma = true ; } buffer . append ( "]" ) ; return buffer . toString ( ) ; }
convert the byte array to the hex dumped string
