Weird thing with JFrame

I noticed something weird when I was using JFrame. When ever I type:

Code java:

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JFrame f = new JFrame();
f.setSize(640,480);

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The part that you can draw to isn't actually 640x480. I'm going to assume that this is because of the top-bar and the side borders. How can I set the drawing portion to exactly 640x480?

I believe the sizes of the title bar and borders of a JFrame are platform dependent, and I am not sure you can retrieve those dimensions (unless perhaps you create your own default look and feel - and even then I'm not sure how to do it). However, if you specify the dimensions of the main JPanel you add to the JFrame you can guarantee the drawable region is the dimension you want

Code java:

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JFrame f = new JFrame();
f.getContentPane().setPreferredSize(new Dimension(640,480));
f.pack();
f.setVisible();

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Thanks alot!