title: Trying to draw a simple rectangle with JPanel, but nothing is showing up
body: <p>I am currently reading the book "Head First Java". The book is amazing and I am really enjoying reading it. But I have come to an abrupt halt. 
  The book was going through GUI programming with the swing library, which turned out to be easier than I thought it would be. After the GUI portion of the chapter the book introduced drawing graphics, with the awt library and graphics objects. And this is where I am stuck. The following is my code, which compiles just fine but does not seem to want to render the rectangle.</p>
  
  <pre><code>import java.awt.*;
  import javax.swing.*;
  
  public class DrawTest
  {
      JFrame frame;
  
      public static void main(String[] args)
      {
          DrawTest test = new DrawTest();
          test.go();
      }
  
      public void go()
      {
          frame = new JFrame();
  
          frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
          frame.setSize(800, 800);
          frame.setVisible(true);
          frame.setResizable(false);
      }
  }
  
  class DrawPanel extends JPanel
  {
      public void paintComponent(Graphics g)
      {
          g.setColor(Color.green);
          g.drawRect(70, 70, 200, 200);
      }
  }
  </code></pre>
  
  <p>What am I doing wrong? It is most likely very obvious, but I am not seeing. I would very much appreciate a thorough answer, I am new to Java so I would like to understand fully.</p>
  
  <p>Thanks in advance!</p>