Content Pane?

Does anyone know what a Content Pane is? Can a component
be added to a JFrame directly or do i have to add it to a content pane first? Im just not sure about the purpose of a Content Pane.

For instance this code produces a runtime error. Do i have to
add the components to a panel then add the panel to a Content Pane then add the content pane to a JFrame? Writing GUI's in Java can be a real pain in the ass. :p

Code:

---

  import java.awt.*;
  import javax.swing.*;
  import java.awt.event.*;
     
 
  public class Test{
  public static void main(String[] args){
      JFrame jf = new JFrame("A Frame"); 
      JPanel jp = new JPanel();
   
      JButton jb = new JButton("A Button");
      JTextArea jta1 = new JTextArea();
      JTextArea jta2 = new JTextArea();
 
      jp.setLayout(new GridLayout(1,2));
      jp.add(jb); 
      jp.add(jta1);
      jp.add(jta2);
       
     
      jf.add(jp);
      jf.setSize(600,300);
      jf.setVisible(true); 
 
    jf.addWindowListener(new WindowAdapter(){
        public void windowClosing(WindowEvent e){
          System.exit(0);
        }
      });
  }
 }

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Never mind i got it. ;)