Length | Tech Tips Tricks

Set Max Character Length Of JTextField

Posted by tech on

May 18, 2010

There is no way to directly set a JTextField‘s maximum character length. The only way for you to do that is to create your own class that inherits the PlainDocument class, instantiate an object of that class and call the JTextField method setDocument().

Below is the source for the custom made MaxLengthTextDocument class.

^?Download MaxLengthTextDocument.java

public class MaxLengthTextDocument extends PlainDocument {
    private int maxChars;
 
    public MaxLengthTextDocument(int length) {
        maxChars = length;
    }
 
    @Override
    public void insertString(int offs, String str, AttributeSet a)throws BadLocationException {
        if(str == null || (getLength() + str.length() > maxChars)){
            str = str.substring(0, maxChars);
        }
        super.insertString(offs, str, a);
    }
}