title: My JFrame always becomes a few pixels too big.
body: <p>I am working on this game in Java, and I just rewrote all my window related code from being based on java.awt to javax.swing. Soon after, I realized that things were a bit more complicated now, and so i did some research and and found out how to draw things, how to set the size of a JFrame, etc. But for some reason, the size of my JFrame always goes 10 pixels beyond the size I've specified it to become. In this case, I wanted it to be 640 by 640 pixels. </p>
  
  <p>Here's my code:</p>
  
  <pre><code>package chrononaut;
  
  import java.awt.*;
  import java.io.IOException;
  import javax.imageio.ImageIO;
  import javax.swing.*;
  
  
  @SuppressWarnings("serial")
  public class GameJFrame extends JFrame 
      {
  
      //Background color:
      static Color bgrCol = new Color(12, 4, 64);
  
      //Size:
      final static int size = 640;
  
      //The component that does the actual drawing:
      static GameJComp drawingComp = new GameJComp();
  
      //Constructor:
      public GameJFrame()
          {
          //Calling super() and setting the title:
          super("Chrononaut");
  
          //Setting icon image:
          try 
          {
          Image icon = ImageIO.read(getClass().getResource("/icon/icon 1.png"));
          setIconImage(icon);
          }
          catch (IOException e) {}
  
          //make it closable:
          setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); 
  
  
          //Setting the size:
          Container c = getContentPane();
          Dimension d = new Dimension(size, size);    //for some reason, it goes 10 pixels beyond the given values
          c.setPreferredSize(d);
          pack();
  
          //Adding the drawing component to the content pane:
          getContentPane().add(drawingComp);
  
          //Making sure the window size stays constant:
          setResizable(false);
  
          //Centering position:
          Toolkit tk = Toolkit.getDefaultToolkit();
          Dimension s = tk.getScreenSize();
          setLocation(s.width/2-getWidth()/2, s.height/2-getHeight()/2);
  
          //Background color:
          setBackground(bgrCol);
  
          //Make it visible:
          setVisible(true);
  
          }
  
  
      public void drawAll()
          {
          drawingComp.drawAll();
          }
  
      public void closeGame()
          {
          dispose();
          System.exit(0);
          }
  
  }
  </code></pre>
  
  <p>When I run it, the space inside the borders of the JFrame appears to have a size of 650 pixels, not 640, even when I call setPreferredSize(d). 
  I tried making Dimension d = new Dimension(size - 10, size - 10); which does seem to work, but I have no idea of weather it would on other platforms. 
  I haven't seen this problem anywhere else on the web, so I have absolutely no idea of why it does this. :(</p>