import java.awt.BorderLayout; 
import java.awt.event.ActionEvent; 
import java.awt.event.ActionListener; 

import javax.swing.AbstractListModel; 
import javax.swing.JCheckBox; 
import javax.swing.JFrame; 
import javax.swing.JLabel; 
import javax.swing.JList; 
import javax.swing.JPanel; 
import javax.swing.JScrollPane; 
import javax.swing.JSpinner; 
import javax.swing.SpinnerNumberModel; 
import javax.swing.SwingUtilities; 
import javax.swing.UIManager; 
import javax.swing.UIManager.LookAndFeelInfo; 
import javax.swing.event.ChangeEvent; 
import javax.swing.event.ChangeListener; 

public class TestThumb { 

public static void main(String[] args) { 
SwingUtilities.invokeLater(new Runnable() { 
@Override 
public void run() { 
new TestThumb().startUi(); 
} 
}); 
} 

private class MyListModel extends AbstractListModel<String> { 

private static final long serialVersionUID = -3791947364926818808L; 

private int size = 10; 

public void setSize(int newSize) { 
if (size != newSize) { 
int oldSize = size; 
size = newSize; 
fireContentsChanged(this, oldSize, newSize); 
} 
} 

@Override 
public int getSize() { 
return size; 
} 

@Override 
public String getElementAt(int index) { 
return "List Element #" + index; 
} 

} 

public void startUi() { 
try { 
for (LookAndFeelInfo info : UIManager.getInstalledLookAndFeels()) { 
if ("Nimbus".equals(info.getName())) { 
UIManager.setLookAndFeel(info.getClassName()); 
break; 
} 
} 
} catch (Exception e) { 
System.err.println("Couldn't set UI to Nimbus: " + e); 
return; 
} 

JFrame frame = new JFrame("Test Scrollbar Thumb"); 
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); 

JPanel content = new JPanel(new BorderLayout()); 

JPanel hdrPanel = new JPanel(); 
hdrPanel.add(new JLabel("JRE Version " + System.getProperty("java.version"))); 
content.add(hdrPanel, BorderLayout.NORTH); 

final MyListModel listModel = new MyListModel(); 

final JList<String> list = new JList<String>(listModel); 

JScrollPane scrollPane = new JScrollPane(list); 
content.add(scrollPane, BorderLayout.CENTER); 

final JSpinner spinner = new JSpinner(new SpinnerNumberModel(10, 0, 10000, 10)); 
spinner.addChangeListener(new ChangeListener() { 

@Override 
public void stateChanged(ChangeEvent e) { 
Object val = spinner.getValue(); 
if (val instanceof Number) { 
Number num = (Number) val; 
listModel.setSize(num.intValue()); 
} 
} 

}); 

final JCheckBox wrap = new JCheckBox("Wrap"); 
wrap.addActionListener(new ActionListener() { 
@Override 
public void actionPerformed(ActionEvent e) { 
list.setLayoutOrientation(wrap.isSelected() ? JList.VERTICAL_WRAP : JList.VERTICAL); 
} 
}); 

JPanel buttonPanel = new JPanel(); 
buttonPanel.add(new JLabel("Items:")); 
buttonPanel.add(spinner); 
buttonPanel.add(wrap); 

content.add(buttonPanel, BorderLayout.SOUTH); 
frame.setContentPane(content); 

frame.pack(); 
frame.setLocationRelativeTo(null); 
frame.setVisible(true); 
} 
}