Question

I’m a beginner in Java, and NetBeans. I’m trying to make a simple program where you introduce 2 numbers and their sum gets divided by two. However, I’m using JFormattedTExtFields and I don’t know how to customize the allowed input in them. Basically I’m trying to find out how to:

• Only allow numbers to be entered in JFormmatedTextField;
• Only allow a certain amount of numbers;

Answer 1

You could use a NumberFormat and specify the maximum number of integer digits with setMaximumIntegerDigits.

Here’s a nice article.

Basically you can do something like:

NumberFormat f = NumberFormat.getNumberInstance(); 
f.setMaximumIntegerDigits(maxDigitsAmount);
JFormattedTextField field = new JFormattedTextField(f);

The Format should guarantee that the inserted String satisfy the format. Anyway even if a number is supplied, the textfield will store it as a String. So if you need your original Integer you need to rebuild it like suggested @noise:

Integer i = Integer.toString(field.getText());