Basic Text Components - The Definitive Guide to Java Swing - page 532

PlainDocument Class
The PlainDocument class is a specific implementation of the AbstractDocument class. It does not
store any character-level attributes for the content. Instead, the elements describe where the
content and each line in the content begin.
The program in Listing 15-6 walks through the Element tree for a PlainDocument , the model
used for both the JTextField and the JTextArea .
Listing 15-6. Element Walker
import java.awt.*;
import java.awt.event.*;
import java.util.*;
import javax.swing.*;
import javax.swing.text.*;
public class ElementSample {
public static void main (String args[]) {
Runnable runner = new Runnable() {
public void run() {
JFrame frame = new JFrame("Element Example");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
final JTextArea textArea = new JTextArea();
JScrollPane scrollPane = new JScrollPane(textArea);
JButton button = new JButton("Show Elements");
ActionListener actionListener = new ActionListener() {
public void actionPerformed(ActionEvent actionEvent) {
Document document = textArea.getDocument();
ElementIterator iterator = new ElementIterator(document);
Element element = iterator.first();
while (element != null) {
System.out.println(element.getStartOffset());
element = iterator.next();
}
}
};
button.addActionListener(actionListener);
frame.add(scrollPane, BorderLayout.CENTER);
frame.add(button, BorderLayout.SOUTH);
frame.setSize(250, 250);
frame.setVisible(true);
}
};
EventQueue.invokeLater(runner);
}
}