title: Java GUI create three JPanel in one JFrame
body: <p>I have a problem with Java GUI.</p>
  
  <p>I want to create three <code>JPanel</code> instances which have size different in one <code>JFrame</code>. <code>JFrame</code> size 300x800 and <code>Panel1</code> 300x200, <code>Panel2</code> 300x100 and <code>Panel3</code> 300x500.  I want to add this panels under by under. </p>
  
  <p>How to solve this problem?</p>