例如，这是一个带有documentFilter的SSCCE，它可以防止用户在文档中键入数字，但允许Swing Timer这样做。
import java.awt.event.*;import java.awt.event.ActionListener;import javax.swing.*;import javax.swing.text.*;public class DocFilterPanel extends JPanel { private Jtextarea textarea = new Jtextarea(12, 50); private MyDocFilter myDocFilter = new MyDocFilter(); public DocFilterPanel() { ((Plaindocument) textarea.getdocument()).setdocumentFilter(myDocFilter); int vsbPolicy = JScrollPane.VERTICAL_SCROLLBAR_ALWAYS; int hsbPolicy = JScrollPane.HORIZONTAL_SCROLLBAR_AS_NEEDED; add(new JScrollPane(textarea, vsbPolicy , hsbPolicy)); int timerDelay = 1000; new Timer(timerDelay , new ActionListener() { @Override public void actionPerformed(ActionEvent e) { myDocFilter.setFilter(false); textarea.append("12345n"); myDocFilter.setFilter(true); } }).start(); } private static void createAndShowGui() { DocFilterPanel docFilterPanel = new DocFilterPanel(); Jframe frame = new Jframe("DocFilterTest"); frame.setDefaultCloseOperation(Jframe.EXIT_ON_CLOSE); frame.getContentPane().add(docFilterPanel); frame.pack(); frame.setLocationByPlatform(true); frame.setVisible(true); } public static void main(String[] args) { SwingUtilities.invokeLater(new Runnable() { public void run() { createAndShowGui(); } }); }}class MyDocFilter extends documentFilter { private static final String REMOVE_REGEX = "\d"; private boolean filter = true; public boolean isFilter() { return filter; } public void setFilter(boolean filter) { this.filter = filter; } @Override public void insertString(FilterBypass fb, int offset, String text, AttributeSet attr) throws BadLocationException { if (filter) { text = text.replaceAll(REMOVE_REGEX, ""); } super.insertString(fb, offset, text, attr); } @Override public void replace(FilterBypass fb, int offset, int length, String text, AttributeSet attrs) throws BadLocationException { if (filter) { text = text.replaceAll(REMOVE_REGEX, ""); } super.replace(fb, offset, length, text, attrs); }}
