Graphical User Interfaces - JavaTech: An Introduction to Scientific and Technical Computing with Java - page 207

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
/** Demonstrate GUI building with multiple panels
* and event handling.
**/
public class MultiPanelWithEvents extends JApplet
implements ActionListener
{
InputsPanel fInputsPanel;
JTextArea fTextOutput;
/** Build the interface with InputsPanel
* and ActionButtonsPanel.
**/
public void init () {
Container content - pane = getContentPane ();
content - pane.setLayout (new GridLayout (1, 3));
// First create a panel of buttons
ActionButtonsPanel buttons - panel =
new ActionButtonsPanel (this);
. ..Rest same as in init() in MultiPanelApplet in
Chapter 6 ...
} // init
// Handle the button events. **/
public void actionPerformed (ActionEvent ae) {
/** Get the values in the two text fields. **/
String str1 = fInputsPanel.fTextfieldTop.getText ();
String str2 = fInputsPanel.fTextfieldBot.getText ();
double val1=0.0;
double val2=0.0;
try {
val1 = Double.parseDouble (str1);
val2 = Double.parseDouble (str2);
} catch (NumberFormatException nfe) {
System.out.println ("Improper input");
}