how to try and catch exceptions with jtextfield?

Question

i'm making a simple gui where the user has to enter 2 random strings of numbers and when the "done" button is pushed it will output those 2 strings. But how do I do this with try-catch method so that the user only can use numbers otherwise it will catch exceptions?

This is my code:

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

public class Panel extends JPanel 
{
    private JTextField field1;
    private JTextField field2;
    private JButton button1;
    private JLabel label1;
    private JLabel label2;

    public Panel() 
    {
        label1 = new JLabel("first string: ");
        label2 = new JLabel("second string: ");
        field1 = new JTextField(38);
        field2 = new JTextField(3);
        button1 = new JButton("done");

        ButtonP buttonP = new ButtonP();
        button1.addActionListener(buttonP);

        this.add(label1);
        this.add(field1);
        this.add(label2);
        this.add(field2);
        this.add(button1);
    }

    private class ButtonP implements ActionListener 
    {   
        public void actionPerformed(ActionEvent e)  
        {
            System.out.println("String 1 " + field1.getText() + " and string 2 " + field2.getText());
        }
    }
}

Thanks in advance

Answer 1

//You save yor recieved string from textfield and try to convert it to an integer
//If is not convertable, it throws an exception and prints in console the error
String string1 = field1.getText();
int myInteger = 0;
try {
    myInteger = Integer.parseInt(string1);
} catch(Exception e){
    System.out.println("Invalid input. Not an integer");
    e.printStackTrace();
}

Hope that helps. Greetings.

Answer 2

You have two options here. The first and the recommended one, is to use a JFormattedTextField in order to eliminate the chance of getting NumberFormatException . Plus, it is more user-friendly.

The second option is to catch the NumberFormatException , and when you catch it, to add a kind of an "error" message to the user (not so much user-friendly) and tell him to give correct input. Then, he miss-clicks a letter, and we are back to the error message.