title: JPanel transparency problem
body: <p>I have a dark-gray <code>JPanel</code> with a <code>JLabel</code> on it. I set <code>new Color(0, 0, 0, .5f)</code> (tranparent) as the background of the <code>JLabel</code> and I change the text several times using a button. The problem is, everytime the text is changed, the previous text still remains behind the new text. I change the text from "123456789" to "1234567", "12345" and "123". Here is the screenshot:</p>
  
  <p><img src="https://i.stack.imgur.com/Ey4Ox.png" alt="alt text"></p>
  
  <p>How do I get rid of this "shadow"?</p>