I want my program to be able to tell if what is inside my two JTextFields is an integer or a String.
CODE
public void actionP
You can process the key event in the action
method also. Try this
First make a JTextField
JTextField j=new JTextField();
Then add KeyListner
to this JTextField as
j.addKeyListener(new KeyListener() {
@Override
public void keyTyped(KeyEvent arg0) {
// TODO Auto-generated method stub
}
@Override
public void keyReleased(KeyEvent arg0) {
// TODO Auto-generated method stub
if(arg0.getKeyCode()>57 || arg0.getKeyCode()<48) {
//your error message and other handling code here
JOptionPane.showMessageDialog(PatentFrame, "Only integer allowed", "Message title",JOptionPane.ERROR_MESSAGE);
}
}
@Override
public void keyPressed(KeyEvent arg0) {
// TODO Auto-generated method stub
}
});
48 is ASCII code for 0 and 57 is ASCII code for 9. You can also ignore virtual keys like shift. See ASCII chart
For restricting a User from entering anything but digits
, you can set a DocumentFilter on the JTextField
.
Here is a small example :
import java.awt.*;
import javax.swing.*;
import javax.swing.text.AbstractDocument;
import javax.swing.text.AttributeSet;
import javax.swing.text.BadLocationException;
import javax.swing.text.DocumentFilter;
import javax.swing.text.DocumentFilter.FilterBypass;
public class InputInteger
{
private JTextField tField;
private MyDocumentFilter documentFilter;
private void displayGUI()
{
JFrame frame = new JFrame("Input Integer Example");
frame.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
JPanel contentPane = new JPanel();
contentPane.setBorder(
BorderFactory.createEmptyBorder(5, 5, 5, 5));
tField = new JTextField(10);
((AbstractDocument)tField.getDocument()).setDocumentFilter(
new MyDocumentFilter());
contentPane.add(tField);
frame.setContentPane(contentPane);
frame.pack();
frame.setLocationByPlatform(true);
frame.setVisible(true);
}
public static void main(String[] args)
{
Runnable runnable = new Runnable()
{
@Override
public void run()
{
new InputInteger().displayGUI();
}
};
EventQueue.invokeLater(runnable);
}
}
class MyDocumentFilter extends DocumentFilter
{
@Override
public void insertString(DocumentFilter.FilterBypass fp
, int offset, String string, AttributeSet aset)
throws BadLocationException
{
int len = string.length();
boolean isValidInteger = true;
for (int i = 0; i < len; i++)
{
if (!Character.isDigit(string.charAt(i)))
{
isValidInteger = false;
break;
}
}
if (isValidInteger)
super.insertString(fp, offset, string, aset);
else
Toolkit.getDefaultToolkit().beep();
}
@Override
public void replace(DocumentFilter.FilterBypass fp, int offset
, int length, String string, AttributeSet aset)
throws BadLocationException
{
int len = string.length();
boolean isValidInteger = true;
for (int i = 0; i < len; i++)
{
if (!Character.isDigit(string.charAt(i)))
{
isValidInteger = false;
break;
}
}
if (isValidInteger)
super.replace(fp, offset, length, string, aset);
else
Toolkit.getDefaultToolkit().beep();
}
}
@Override
public void insertString(FilterBypass fb, int off
, String str, AttributeSet attr)
throws BadLocationException
{
// remove non-digits
fb.insertString(off, str.replaceAll("\\D++", ""), attr);
}
@Override
public void replace(FilterBypass fb, int off
, int len, String str, AttributeSet attr)
throws BadLocationException
{
// remove non-digits
fb.replace(off, len, str.replaceAll("\\D++", ""), attr);
}
Not sure exactly where in your code the test is being performed, but you can use this method to determine if a String is an integer:
public static boolean isInteger(String s) {
try {
Integer.parseInt(s);
} catch(NumberFormatException e) {
return false;
}
// if exception isn't thrown, then it is an integer
return true;
}
Less expensive none exception based way, assuming your code does not need to throw an exception:
public static boolean isInt(String s){
for(int i = 0; i < s.length(); i++){
if(!Character.isDigit(s.charAt(i))){
return false;
}
}
return true;
}