Supermarket operation support system - Software Development Case Studies in Java - page 359

System.out.println(e.getActionCommand() !
" action performed");
if (lastInputField! # null ){
String text # lastInputField.getText();
if (cmd.equals("C")){
if (text.length()>0){
lastInputField.setText(text.
substring(0,text.length()-1));
}
} else {
lastInputField.setText(text ! cmd);
}
lastInputField.requestFocus();
}
}
}
The BarCodeListener interface is quite simple; it contains one method that
is called when a new bar code is read.
package CounterUI;
public interface BarCodeListener {
void readValue(BarCodeReaderEvent event);
}
The information relating to a new bar code read is stored in BarCode
ReaderEvent objects. In our case the only information is represented by the
code.
package CounterUI;
public class BarCodeReaderEvent {
String code;
BarCodeReaderEvent(String code){
this .code # code;
}
String getCode() { return code; }
}
The simulated bar code reader is implemented as a frame: BarCode
ReaderUI . Each bar code is an image stored on the hard disk and used as an
icon for a button. When a button is pressed the listener is notified that the
corresponding code has been read.
package CounterUI;
import java.awt.*;
import javax.swing.*;
import java.awt.event.*;
public class BarCodeReaderUI extends JFrame {
private JButton btProduct1 # new JButton();