FULL PRODUCT VERSION :
java version "1.8.0_60"
Java(TM) SE Runtime Environment (build 1.8.0_60-b27)
Java HotSpot(TM) 64-Bit Server VM (build 25.60-b23, mixed mode)


ADDITIONAL OS VERSION INFORMATION :
Linux marvin 3.13.0-24-generic #47-Ubuntu SMP Fri May 2 23:30:00 UTC 2014 x86_64 x86_64 x86_64 GNU/Linux


A DESCRIPTION OF THE PROBLEM :
When using Nimbus look and feel, the scrollbar thumb disappears if its size gets below approximately 24 pixels.
 

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
Resize any scrollbar so that the thumb becomes small.

EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
The scrollbar thumb should remain visible, at a reasonable minimum size.
ACTUAL -
The scrollbar thumb disappears once it reaches approximately 24 pixels.

REPRODUCIBILITY :
This bug can be reproduced always.

---------- BEGIN SOURCE ----------
import javax.swing.*;

public class ScrollTest {
    public static void main(String[] args) throws Exception {
        for (UIManager.LookAndFeelInfo info :
		 UIManager.getInstalledLookAndFeels()) {
            if (info.getName().startsWith("Nimbus")) {
                UIManager.setLookAndFeel(info.getClassName());
                break;
            }
        }

        final JFrame frame = new
	    JFrame(ScrollTest.class.getSimpleName());
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        JTextArea textArea = new JTextArea();
        textArea.setColumns(80);
        textArea.setRows(40);
	textArea.setFont(new java.awt.Font("Monospaced", 0, 12));

        final JScrollPane scrollPane = new JScrollPane(textArea);
        scrollPane.setHorizontalScrollBarPolicy(JScrollPane.HORIZONTAL_SCROLLBAR_AS_NEEDED);
        scrollPane.setVerticalScrollBarPolicy(JScrollPane.VERTICAL_SCROLLBAR_AS_NEEDED);
        frame.getContentPane().add(scrollPane);
        frame.pack();
        frame.setVisible(true);
    }
}

---------- END SOURCE ----------