Re: Help to correct error

Knute Johnson <>
Sat, 02 Aug 2008 15:41:06 -0700
bH wrote:

Hi All,
On opening this program for the first time, I get these errors listed
below. After the data entry and button press I get no error. Using IE
lastest version Tools menu item click to get Sun Java Console to see
this error.

I would appreciate help to correct "on opening up error"


Exception in thread "AWT-EventQueue-2"
java.lang.NumberFormatException: For input string: ""
    at java.lang.NumberFormatException.forInputString(Unknown Source)
    at java.lang.Integer.parseInt(Unknown Source)
    at java.lang.Integer.parseInt(Unknown Source)
    at JustaTest.paint(
    at javax.swing.RepaintManager.paintDirtyRegions(Unknown Source)
    at javax.swing.RepaintManager.paintDirtyRegions(Unknown Source)
    at javax.swing.RepaintManager.seqPaintDirtyRegions(Unknown Source)
    at javax.swing.SystemEventQueueUtilities
$ Source)
    at java.awt.event.InvocationEvent.dispatch(Unknown Source)
    at java.awt.EventQueue.dispatchEvent(Unknown Source)
    at java.awt.EventDispatchThread.pumpOneEventForFilters(Unknown
    at java.awt.EventDispatchThread.pumpEventsForFilter(Unknown Source)
    at java.awt.EventDispatchThread.pumpEventsForHierarchy(Unknown
    at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
    at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
    at Source)

import java.awt.*;
import javax.swing.*;
import java.awt.event.*;

//<applet code ="JustaTest.class" width=300 height=350></applet>

public class JustaTest extends JApplet implements ActionListener {
  Label introLbl = new Label(" Show A Circle");
  Label directionsLbl = new Label(" Enter #'s of Your Color and
  JTextField NumbrColorTxtFld = new JTextField(4); // input color

     JTextField NumbrColorTxtFld = new JTextField("0",4);

  JTextField MeasDiaCircleTxtFld = new JTextField(4);
  Label choiceNumbrSidesLbl = new Label("Enter a 1(red),2(green),
  Label measCircleLbl = new Label("Limit Entry to Measure > 0 and
  Label calculateButtnLbl = new Label( "Click Button to Show ");
  JButton calculateButtn = new JButton("Paint It");

  public void init() {
    Container con = getContentPane();
    con.setLayout(new FlowLayout());

  public void paint(Graphics g) {
// int colorNumber = Integer.parseInt(NumbrColorTxtFld.getText());

       int colorNumber;
       try {
         colorNumber = Integer.parseInt(NumberColorTxtFld.getText());
       } catch (NumberFormatException nfe) {
         System.out.println("bad number in NumberColorTxtFld");
         colorNumber = 0;

    System.out.println("NumbrColor = "+ colorNumber);
    int measureDia = Integer.parseInt(MeasDiaCircleTxtFld.getText());
    if ((measureDia<1)||(measureDia>150)){
      measureDia = 3;
    System.out.println("measureDia = "+ measureDia);
    switch (colorNumber){
      case 1:
      case 2:
      case 3:
  public void actionPerformed(ActionEvent thisEvent) {
    System.out.println("inside ActionEvent");
    Object source = thisEvent.getSource();
    if (source == calculateButtn){

paint() is called when an Applet or application is being drawn the first
time. You are throwing an exception because there is no data in the
NumbrColorTxtFld the first time the applet is drawn. Just catch the
exception or put some value in the NumbrColorTxtFld when you create it.

See your code above.


Knute Johnson
email s/nospam/knute2008/

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