Listing 1: Connect to Database using Protocol Operands
// Connect to database
public void connectDB ( String []  operand )
                   throws Exception {
    if (operand[DBP_DRIVER_ARG] != null ) {
      class.forName( operand[DBP_DRIVER_ARG]);
    }
    if (operand[DBP_USERID_ARG] ==  null) {
       session =
       DriverManager.getConnection(
         operand[DBP_URL_ARG]);
    }
    else {
        session =
            DriverManager.getConnection(
      operand[DBP_URL_ARG],
      operand[DBP_USERID_ARG],
      operand[DBP_PASSWORD_ARG]  );
    }
    query =  session.createStatement();
}

Listing 2: The User Interface is notified of Observable change with a ProtocolData Object.
class DataBrowser
         extends Frame
         implements DBProtocol,
                            DBConstants,
                            DBHandle,
                            ItemListener,
                            Observer {
…

        public void update(  Observable o,
                                         Object p) {
               if !(p instanceof ProtocolData)){
                    System.out.println("Error in
                                   Observers.");
                    System.exit(1);
               }
              // do something as directed by
              // observable object with detail
              // in the protocol, e.g. requery
      }}

Listing 3: The Protocol Client creates a Protocol Instruction.
public static void  tellProtocolClient( byte opcode )
                                   throws Exception {
    ProtocolData protocolData =
            ProtocolData.getProtocolData();
    protocolData.setOpcode(opcode);
    try {
        switch (opcode) {
            case DBP_EXECUTE_QUERY: {
                   // the TextArea is the operand value
                  protocolData.setOperand(
                              ui.queryWindow.getText(),
                              DBP_SQLTEXT_ARG);
                  protocolData.setOperand(
                             ui.rowCount.getText(),
                             DBP_ROWCOUNT_ARG);
                  ProtocolServer.serviceDBRequest(
                              protocolData);
                  break;
 }
…
}

Listing 4: Protocol Server Instruction Handling.
// protocol handler
public static Object serviceDBRequest( ProtocolData p )
                                throws Exception {
    switch (p.getOpcode()) {
        case DBP_EXECUTE_QUERY: {
            db.execSQL(
                 p.getOperand(DBP_SQLTEXT_ARG),
                 p.getOperand(DBP_ROWCOUNT_ARG));
 return db.getResults();
        }
…
}

Listing 5: ProtocolData Class Operand Capture
public void setOpcode( int opcode ) {
    this.opcode = opcode;
}
public void setOperand( String operand, int index  ) {
    this.operand[index] = operand;
}

Listing 6: Anonymous Class Example One
tableList.addItemListener(
    new ItemListener() {
        public void itemStateChanged(
                              ItemEvent e ) {
            Integer index =  (Integer)e.getItem();
            tableName = tableList.getItem(index.intValue());
            try {
                ProtocolClient.tellProtocolClient(
                                         DBP_COLUMNS );
            } catch (Exception ea) {
                 ea.printStackTrace();
            }
       } });

Listing 7: Anonymous Class Example Two.
queryButton.addActionListener(
        new ActionListener() {
            public void actionPerformed(
                               ActionEvent e ){
                tabOptions.show(
                          panel4,
                          queryButton.getLabel());
          } });