How to remove all values ​​except numbers from a string variable?

Question

Java

When you start the program, a window opens in which you can enter text, you need to somehow remove all the characters ( that the user entered ) except for numbers from this field (or a variable into which data is written from the field), how can this be done?

Answer 1

You can define a PlainDocument or DocumentListener that accepts only numbers and hang it on the input field.