public class Nfc

Nfc nfc = Nfc.getInstance();
if (!nfc.canRead()) {
    // device has no NFC or it is disabled
    return;
}
nfc.readTag(new NfcReadOptions()
        .setNdefOnly(true)
        .setAlertMessage("Hold near the poster"))
   .onResult((tag, err) -> {
        if (err != null) {
            return;
        }
        tag.readNdef().onResult((msg, e) -> {
            if (e == null) {
                String url = msg.getFirstRecord().getUriPayload();
                // launch / display url
            }
        });
   });

nfc.readTag(new NfcReadOptions()
        .setTechFilter(TagType.ISO_DEP)
        .setIsoSelectAids(myAid))
   .onResult((tag, err) -> {
        if (err != null) return;
        IsoDep iso = tag.getIsoDep();
        if (iso == null) return;
        iso.transceive(myCommandApdu).onResult((resp, e) -> {
            if (ApduResponse.isSuccess(resp)) { ... }
        });
   });

class MyService extends HostCardEmulationService {
    public String[] getAids() { return new String[] { "F0010203040506" }; }
    public byte[] processCommand(byte[] apdu) {
        return ApduResponse.withStatus(new byte[] { 'O', 'K' },
                ApduResponse.swSuccess());
    }
}
Nfc.getInstance().registerHostCardEmulationService(new MyService());