Java - quiero hacer una barra de progreso con hilos

import java.awt.BorderLayout;

import java.awt.event.ActionEvent;

import java.awt.event.ActionListener;

import javax.swing.BorderFactory;

import javax.swing.JButton;

import javax.swing.JFrame;

import javax.swing.JPanel;

import javax.swing.JProgressBar;

import javax.swing.SwingUtilities;

public class BarraProgreso extends JFrame {

	private JProgressBar barra;

	private JButton btMenos;

	private JButton btMas;

	private HiloBarra hiloBarra;

	public BarraProgreso() {

		barra = new JProgressBar();

		barra.setMaximum(100);

		barra.setMinimum(0);

		barra.setValue(50);

		btMenos = new JButton("Disminuye");

		btMenos.addActionListener(new AccionBotones());

		btMas = new JButton("Aumenta");

		btMas.addActionListener(new AccionBotones());

		hiloBarra = new HiloBarra();

		JPanel pnBarra = new JPanel();

		pnBarra.add(barra);

		pnBarra.setBorder(BorderFactory.createCompoundBorder(

				BorderFactory.createEmptyBorder(30, 40, 30, 40),

				BorderFactory.createRaisedSoftBevelBorder()));

		JPanel pnBotones = new JPanel();

		pnBotones.add(btMenos);

		pnBotones.add(btMas);

		setLayout(new BorderLayout());

		add(pnBarra, BorderLayout.CENTER);

		add(pnBotones, BorderLayout.SOUTH);

		setTitle("Prueba Barra");

		setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

		pack();

		setLocationRelativeTo(null);

		setVisible(true);

	}

	private class HiloBarra extends Thread {

		boolean aumentar = true;

		@Override

		public void run() {

			while(true) {

				try {

					Thread.sleep(100);

					if (aumentar)

						barra.setValue(barra.getValue() + 1);

					else

						barra.setValue(barra.getValue() - 1);

				} catch (InterruptedException e) {

					e.printStackTrace();

				}

			}

		}

	}

	private class AccionBotones implements ActionListener {

		@Override

		public void actionPerformed(ActionEvent e) {

			if (!hiloBarra.isAlive())//Si no está "vivo"..

				hiloBarra.start();//..lo iniciamos

			JButton btActivado = (JButton)e.getSource();

			if (btActivado.equals(btMas))

				hiloBarra.aumentar = true;

			else

				hiloBarra.aumentar = false;

		}

	}

	public static void main(String[] args) {

		SwingUtilities.invokeLater(new Runnable() {

			@Override

			public void run() {

				new BarraProgreso();

			}

		});

	}

}