title: Vertical progress bar has strange background which is not changeable
body: <p>The progress bar is created by the following code</p>
  
  <pre><code>    bar = new JProgressBar(JProgressBar.VERTICAL);
      bar.setEnabled(true);
  
      bar.setBackground(Color.YELLOW);
      bar.setForeground(Color.GREEN);
  
      bar.setStringPainted(true);     
  
      getReflectedComponent().setLayout(new BorderLayout());
      getReflectedComponent().add(bar, BorderLayout.CENTER);
  </code></pre>
  
  <p>Note that getReflectedComponent() returns a JComponent. In another method the displayed String the max value and the current value are manipulated, not more.</p>
  
  <p>I really have no idea why this very strange grey stripes are displayed at the top. If I display the progress bar horizontally they are not there...</p>
  
  <p><img src="https://i.stack.imgur.com/WvBaq.png" alt="This is how my progress bar looks like"></p>