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import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JTextField;
import javax.swing.text.AttributeSet;
import javax.swing.text.BadLocationException;
import javax.swing.text.Document;
import javax.swing.text.PlainDocument;
public class MaxLengthDocument extends PlainDocument {
private int max;
public MaxLengthDocument(int maxLength) {
max = maxLength;
}
public void insertString(int offset, String str, AttributeSet a) throws BadLocationException {
if (getLength() + str.length() > max)
java.awt.Toolkit.getDefaultToolkit().beep();
else
super.insertString(offset, str, a);
}
}
class MainClass{
public static void main(String[] a){
Document doc = new MaxLengthDocument(5); // set maximum length to 5
JTextField field = new JTextField(doc, "", 8);
JPanel flowPanel = new JPanel();
flowPanel.add(field);
JFrame frame = new JFrame("MaxLengthDocument demo");
frame.setContentPane(flowPanel);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setSize(160, 80);
frame.setVisible(true);
}
}
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