I bought a USB RFID reader/writer to develop an attendance application. Along with the device they given VB example to read/write RFID tags. But i want to do this in java. Is there any way to start programing which read/write the RFID tags.
I would suggest getting started by googling for java USB APIs. I stumbled on this one: http://jusb.sourceforge.net/ and it doesn't look too bad.
If the reader is actually run through a serial converter (look it up in the manual) you could use rxtx library to connect to this device.
And one more thing i want to know, does RFID reader continuously read the RFID tags when ever they come into reader range? If it is, how to get the tag data?
Once you have the USB-Port managed, you read its input stream and get a stream of bytes. The manufacturer of the reader should have a description on how to parse these bytes into actual tagcodes. Or just re-engineer the VB code.