I develop secure smart card applications that can run on any Java Card OS compatible card or card reader.

The less secure QRCode and Barcode Scanners etc can be read by any compatible device and without any security such as encryption during the transaction. Smart Cards are more suitable for controlled environments or operations requiring the secure storage and exchange of data from the chip stored on the smart card, to a compatible reader. This process is executed via a compatible front end which is built upon Java (javax.smartcardio) Library containing specific Application Programming Device Unit (APDU) commands to be sent to the reader to communicate with the card.

More information about smart cards can be found at https://www.securetechalliance.org/smartcards-faq