Setting Up a JTextField to only accept Integers - Solution! (with Questions)

[Declan Dee]

Hi,

I was asked during my course to set up a JTextfield to make sure that only integers are accepted. I spent ages on several forums looking for a solution but I could not find anything.

Luckily I manged to find a solution, but unfortunatly I am not 100% what I have typed and I would love to know excatly what it is. Its works perfectly by the way.

You can type only integers and nothing else

    
try {
                     int1 = Integer.parseInt(JTextField.getText());   //This was a string coming from a resultset that I changed into and Int
                     JTextField.requestFocusInWindow();
                     } catch (Exception z) { 
                         JOptionPane.showMessageDialog(this, "Incorrect Data Type! Numbers Only!",
                            "Inane error", JOptionPane.ERROR_MESSAGE);
                         JTextField.setText("");
                         JTextField.requestFocusInWindow();
                         return;
                }

Any explination? - Thanks in advance

Good to finally have a solution!

You have no idea how long I was looking for this!

[marc weber]

Congratulations on getting it to work!

Integer's parseInt method throws a NumberFormatException if the String parameter cannot be parsed as an int. This is the exception you're catching if the String returned by getText contains something other than digits.

But...

There are ways to do this without throwing an exception. I don't know the "best" way, but one approach is to consider that a String is a sequence of characters, and the Character class has a method isDigit. You could test the user's input and keep asking them to correct it until it satisfies your condition.

[pete stein]

Other possible Swing solutions: use a JFormattedTextField instead of a JTextField, or you could use a JTextField and add a DocumentFilter to the PlainDocument that the JTextField holds.

[Michael Dunn]

> I spent ages on several forums looking for a solution but I could not find anything.

you need to sharpen your research skills

JTextField is a Swing component
the ranch has a Swing Forum
the Swing forum has an FAQ
the FAQ has this listing

NumericTextField - how to create a text field that only accepts numbers as input

[marc weber]

Michael Dunn wrote:... NumericTextField - how to create a text field that only accepts numbers as input

Nice!

(Like I said above, "I don't know the 'best' way...")

[Declan Dee]

Hi,

Of course it can be made even simpler:

    

try {
                     ticketAmnt = Integer.parseInt(selectTickets.getText());
                     
                     } catch (Exception z) { 
                         JOptionPane.showMessageDialog(this, "Nice Try",
                            "Inane error", JOptionPane.ERROR_MESSAGE);
                         selectTickets.setText("");
                         return;
                }

However there is one BIG problem. When using this you can enter a minus number and it will be accepted