JTextField: How to limit the number of characters?

[Darya Akbari]

Is there a way to limit the number of characters (digits) in a JTextField?

Regards,
Darya

[Stuart Gray]

If it is for digits, use a JFormattedTextField with a NumberFormat instance. e.g:

NumberFormat f = NumberFormat.getInstance();
f.setMaximumIntegerDigits(3);
f.setMaximumFractionDigits(2);
JFormattedTextField field = new JFormattedTextField(f);

This will limit the input to the form nnn.nn.

[Craig Wood]

Implementing a Document Filter on the Text Component Features page of the tutorial.

[Darya Akbari]

Thanks for your responses.

But I need the JTextField as an input text field with maximum size of 8 digits.

I don't like the Document Filter because it's too complicate. Since I use JDK 1.4.2 I want some new approach.

Any hints?

Regards,
Darya

[Lionel Badiou]

Hello Darya,

Maybe you could use JSpinner(ready-to-use component to ensure digit inputs with "legal" values).

Hope that helps,

[Darya Akbari]

Hi Lionel,

thanks for the info. Honestly I've never heard about the JSpinner . But that's all too complicate.

I'll stay with a simple solution and check the input String length and throw a Message as shown below:

JTextField tf = new JTextField(8);
if ([B](tf.getText()).length()[/B] > 8) {
    // throw warning
} 

Thanks for your answers.

Regards,
Darya

[Lionel Badiou]

Hello Darya,

Feel free to choose the solution that suits your needs. Be careful yet, your code does not guarantee that user enters only digits. So, you need one more check and consequently one more error message. This is the kind of things that JSpinner manages automatically. The use of JSpinner is as simple as calling a contructor but actually, this component is suitable mainly for small numbers (like page number).

Best regards,

[Darya Akbari]

Hi Lionel,

thanks again for your answer. In my case it's also acceptable when the user enters a alpha-numerical value, which is not correct but as my SCJD assignment says:

The system you are writing does not interact with these numbers, rather it simply records them.

So the user is responsible to input the right number.

But beside of my SCJD assignment and if it's not too much :roll: please send a solution how you would replace my code snippet with JSpinner.

Regards,
Darya