question: public List < byte [ ] > tryDecode ( final String targetToken ) { final ByteBuffer payloadBuf = extractValidPayloadFields ( targetToken ) ; if ( payloadBuf == null ) { return null ; } final List < byte [ ] > fields = new ArrayList < > ( ) ; try { byte [ ] field = null ; while ( ( field = tryReadPayloadNextField ( payloadBuf ) ) . length > 0 ) { fields . add ( field ) ; if ( fields . size ( ) > MAX_FIELD_SIZE ) { return null ; } } return fields ; } catch ( final BufferUnderflowException e ) { return null ; } }
target:  return null if token is malformed or expired