JFormattedTextField-如何只允许使用字符？

Question

I've got an ArrayList of Characters and I've also got a JTextField which returns a String. I was wondering how do I only permit chars to be entered? Or perhaps how could I only allow the first letter of the string to get passed?

Answer 1

So you only want to allow certain chars to be entered, chars that are held by an ArrayList? If so, I'd use a JTextField and then add a DocumentFilter to its Document.

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Edit
Based on your comment:

I want the input to be of type Character. By default I can type in 'a' into my JTextField and it will come out as type String whereas I want it to be of type Character. So If I have a method that passes in a char, and I try and pass in a String it doesn't work and I need it to be a char instead.

You've got an XY Problem here meaning your barking up the wrong tree and looking for the wrong solution, an impossible and illogical one. A JTextField will always hold Strings. Just get the char array from the String, charArray() and then use it.