From Forum Nokia Wiki

This is the code for the JAR file in order to compile a real Java Card CAP File and put into the secure element of the Nokia 6131 (make sure you have either G&D SmartC@fe, SUN's JavaCard Developer Kit for JavaCard or JCOP Tools at hand). Download appropriate Eclipse/JCOP Project: File:Ticket Applet.zip.

/**
 * Implementation of very simple wallet. The Wallet Container holds a
 * value (byte) which can be increase, decreased and read by sending
 * an appropriate APDU
 */
package congress;
 
import javacard.framework.APDU;
import javacard.framework.ISO7816;
import javacard.framework.Applet;
import javacard.framework.ISOException;
 
/**
 * @author gmadlmay
 * 
 */
public class Ticketing extends Applet {
 
	/**
	 *  command set for communication between the
	 *  J2ME application and Java Card Applet as well as
	 *  the Java card Applet and the external reader
	 */
 
	// Command (APDU INS) for increading the value in the wallet
	private final static byte INS_INC = 0x01;
 
	// Command (APDU INS) for decreading the value in the wallet
	private final static byte INS_DEC = 0x02;
 
	// command (APDU INS) for reading the value in the wallet
	private final static byte INS_READ = 0x03;
 
	// variable holding the amount stored in the wallet. 
	private byte value = (byte) 0x20;
 
	public static void install(byte[] bArray, short bOffset, byte bLength) {
		// GP-compliant JavaCard applet registration
		new Ticketing()
				.register(bArray, (short) (bOffset + 1), bArray[bOffset]);
	}
 
	public void process(APDU apdu) {
		// Good practice: Return 9000 on SELECT
		if (selectingApplet()) {
			return;
		}
 
		// grab the byte-array of the APDU
		byte[] buf = apdu.getBuffer();
 
		// check the INS Byte of the APDU and take
		// the appropriate action
		switch (buf[ISO7816.OFFSET_INS]) {
 
		// increase the value in the wallet
		case (byte) INS_INC:
			if (value < 0xff)
				value++;
 
			// return no error, in case everything was okay
			ISOException.throwIt(ISO7816.SW_NO_ERROR);
			break;
 
		// increase the value in the wallet
		case (byte) INS_DEC:
			if (value > 0x00)
				value--;
			// return no error, in case everything was okay
			ISOException.throwIt(ISO7816.SW_NO_ERROR);
			break;
 
		// read the value of the wallet
		case (byte) INS_READ:
 
			// create a byte array out of the value (length: 1)
			byte[] outBuffer = new byte[1];
			outBuffer[0] = value;
 
			// now send back the data.
			apdu.setOutgoing();
			apdu.setOutgoingLength((byte) outBuffer.length);
			apdu.sendBytesLong(outBuffer, (short) 0, (byte) outBuffer.length);
 
			break;
 
		// all other INS
		default:
			// good practice: If you don't know the INStruction, say so:
			ISOException.throwIt(ISO7816.SW_INS_NOT_SUPPORTED);
		}
	}
}