Using getContentPane() in JFrame class

Question

Hello,
I'm reading Bruce Eckel's book.
In chaapter 14, I read TextArea.java.
My question is:
What is the purpose of getContentPane() in the constructor TextArea() in the code below ?
Isn't JFrame IS a Container ? why bother to get another Container ?
import javax.swing.*;
import java.awt.event.*;
import java.awt.*;
import java.util.*;
import com.bruceeckel.swing.*;
import com.bruceeckel.util.*;
public class TextArea extends JFrame {
private JButton
b = new JButton("Add Data"),
c = new JButton("Clear Data");
private JTextArea t = new JTextArea(20, 40);
private Map m = new HashMap();
public TextArea() {
// Use up all the data:
Collections2.fill(m, Collections2.geography,
CountryCapitals.pairs.length);
b.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
Iterator it = m.entrySet().iterator();
while(it.hasNext()) {
Map.Entry me = (Map.Entry)(it.next());
t.append(me.getKey() + ": "+ me.getValue()+"\n");
c.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
t.setText("");
Container cp = getContentPane();
cp.setLayout(new FlowLayout());
cp.add(new JScrollPane(t));
cp.add(b);
cp.add(c);
public static void main(String[] args) {
Consoleb.run(new TextArea(), 475, 425);
}

Answer 1

I appreciate the reply.
There are endless API to read.
I found this:
For conveniance JFrame, JDialog, JWindow, JApplet and
JInternalFrame, by default, forward, by default, all
calls to the add, remove and setLayout methods, to
the contentPane. This means you can call:
rootPaneContainer.add(component);That was introduced in 1.5. May people still use older versions of Java, so use that add method with caution. I myself see no reason to use it, since it is a bit of a hack.
Another question on the side:
How can I remove a topic that I created ?Like karma, no thread ever goes away :-)