My code is throwing an expected error too early. I was trying to test input validation, but I'm throwing an error before validation occurs. When I tried restoring my code to a previous version that worked perfectly fine it throws the same error I'm dealing with now before it was a problem.
The code below is line 137 - the apparent offender
int playerGuess = Integer.parseInt(playerGuessField.getText().trim());
private void guessButtonClicked(){
Validators validGuess = new Validators(this);
int guessesRemaining = Integer.parseInt(guessesRemainingField.getText());
int playerGuess = Integer.parseInt(playerGuessField.getText().trim());//error is thrown here
if(validGuess.isValidGuess(playerGuessField, "guess")){
//more code here but not necessarily relevant
}
}
//basic structure of my validators
public boolean isValidGuess(JTextComponent c, String fieldName){
try {
int validGuess = Integer.parseInt(c.getText());
if(validGuess >= 1 && validGuess <= 10){
return true;
} else {
showErrorDialog("Your " + fieldName + " must be between 1 & 10");
c.requestFocusInWindow();
return false;
}
} catch (NumberFormatException e) {
showErrorDialog("Your " + fieldName + " must be between 1 & 10");
c.requestFocusInWindow();
return false;
}
}
Here's the exception in all it's glory.
Exception in thread "AWT-EventQueue-0" java.lang.NumberFormatException: For input string: "asdf"
at java.base/java.lang.NumberFormatException.forInputString(NumberFormatException.java:67)
at java.base/java.lang.Integer.parseInt(Integer.java:660)
at java.base/java.lang.Integer.parseInt(Integer.java:778)
at GameGUI.guessButtonClicked(GameGUI.java:137)
at GameGUI.lambda$0(GameGUI.java:94)
at java.desktop/javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:1972)
at java.desktop/javax.swing.AbstractButton$Handler.actionPerformed(AbstractButton.java:2313)
at java.desktop/javax.swing.DefaultButtonModel.fireActionPerformed(DefaultButtonModel.java:405)
at java.desktop/javax.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:262)
at java.desktop/javax.swing.plaf.basic.BasicButtonListener.mouseReleased(BasicButtonListener.java:279)
at java.desktop/java.awt.Component.processMouseEvent(Component.java:6617)
at java.desktop/javax.swing.JComponent.processMouseEvent(JComponent.java:3342)
at java.desktop/java.awt.Component.processEvent(Component.java:6382)
at java.desktop/java.awt.Container.processEvent(Container.java:2264)
at java.desktop/java.awt.Component.dispatchEventImpl(Component.java:4993)
at java.desktop/java.awt.Container.dispatchEventImpl(Container.java:2322)
at java.desktop/java.awt.Component.dispatchEvent(Component.java:4825)
at java.desktop/java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4934)
at java.desktop/java.awt.LightweightDispatcher.processMouseEvent(Container.java:4563)
at java.desktop/java.awt.LightweightDispatcher.dispatchEvent(Container.java:4504)
at java.desktop/java.awt.Container.dispatchEventImpl(Container.java:2308)
at java.desktop/java.awt.Window.dispatchEventImpl(Window.java:2773)
at java.desktop/java.awt.Component.dispatchEvent(Component.java:4825)
at java.desktop/java.awt.EventQueue.dispatchEventImpl(EventQueue.java:772)
at java.desktop/java.awt.EventQueue$4.run(EventQueue.java:721)
at java.desktop/java.awt.EventQueue$4.run(EventQueue.java:715)
at java.base/java.security.AccessController.doPrivileged(AccessController.java:391)
at java.base/java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:85)
at java.base/java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:95)
at java.desktop/java.awt.EventQueue$5.run(EventQueue.java:745)
at java.desktop/java.awt.EventQueue$5.run(EventQueue.java:743)
at java.base/java.security.AccessController.doPrivileged(AccessController.java:391)
at java.base/java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:85)
at java.desktop/java.awt.EventQueue.dispatchEvent(EventQueue.java:742)
at java.desktop/java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:203)
at java.desktop/java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:124)
at java.desktop/java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:113)
at java.desktop/java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:109)
at java.desktop/java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:101)
at java.desktop/java.awt.EventDispatchThread.run(EventDispatchThread.java:90)
Bottom line: You need to validate your input.
To do this, I can think of a few options:
Scanner to check if the input is numericScanner scanner = new Scanner(playerGuessField.getText().trim());
if (scanner.hasNextInt()) {
int playerGuess = scanner.nextInt();
} else {
// handle the error
}
try/catchint playerGuess = 0;
try {
playerGuess = Integer.parseInt(playerGuessField.getText().trim());
} catch (NumberFormatException nfe) {
// handle the exception
}
For this, you need to create an input verifier
public class MyInputVerifier extends InputVerifier {
@Override
public boolean verify(JComponent input) {
String text = ((JTextField) input).getText();
try {
BigDecimal value = new BigDecimal(text);
return true; // or some other evaluation (i.e. value > 0 for positive value)
} catch (NumberFormatException e) {
return false;
}
}
}
Then, you need to add it to the field
field.setInputVerifier(new MyInputVerifier());
And lastly, you need to trigger the verification. This is typically done when the form is rendered. My example is using an ActionListener.
btn.addActionListener(e -> {
if (!field.getInputVerifier().verify(field)) {
System.out.println("Not valid. Clear!");
field.setText("");
}
});
DocumentListenerpublic class InputVerifierDemo {
private static JLabel errorMsg = new JLabel("Invalid input");
private static JFrame frame = new JFrame();
public static void main(String[] args) {
JTextField field = new JTextField(10);
// field.setInputVerifier(new MyInputVerifier());
JButton btn = new JButton("Click Me!");
// btn.addActionListener(e -> {
// if (!field.getInputVerifier().verify(field)) {
// System.out.println("Not valid. Clear!");
// field.setText("");
// }
// });
JPanel panel = new JPanel();
errorMsg.setForeground(Color.RED);
errorMsg.setVisible(false);
panel.setLayout(new GridBagLayout());
GridBagConstraints c = new GridBagConstraints();
c.insets = new Insets(5, 0, 0, 5);
c.gridx = 1;
c.gridy = 0;
c.anchor = GridBagConstraints.SOUTH;
panel.add(errorMsg, c);
c.gridx = 1;
c.gridy = 1;
c.anchor = GridBagConstraints.CENTER;
panel.add(field, c);
field.getDocument().addDocumentListener(new DocumentListener() {
@Override
public void removeUpdate(DocumentEvent e) {
validateInput(field);
}
@Override
public void insertUpdate(DocumentEvent e) {
validateInput(field);
}
@Override
public void changedUpdate(DocumentEvent e) {
} // Not needed for plain-text fields
});
frame.getContentPane().add(panel);
frame.setSize(400, 400);
frame.setLocationRelativeTo(null);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setVisible(true);
}
private static void validateInput(JTextField field) {
String text = field.getText();
String pattern = "\\d+";
Pattern r = Pattern.compile(pattern);
Matcher m = r.matcher(text);
if (m.matches()) {
errorMsg.setVisible(false);
} else {
errorMsg.setVisible(true);
}
}
private static class MyInputVerifier extends InputVerifier {
@Override
public boolean verify(JComponent input) {
String text = ((JTextField) input).getText();
try {
BigDecimal value = new BigDecimal(text);
return true; // or some other evaluation (i.e. value > 0 for positive value)
} catch (NumberFormatException e) {
return false;
}
}
}
}
The code above contain the input verifier AND the document listener solutions so that you could play with both. I personally prefer the document listener because it is more interactive. I rather validate fields as I am typing on them, rather than after the fact when all the fields are filled and an action to submit the form takes place. But, this is all a matter of personal preference.
I credit MadProgrammer for option #1.