VisualMetronome - [Java]

VisualMetronome.java

package swingapplications;

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;

// A visual metronome that displays 4/4 time count.
class VisualMetronome implements ActionListener, Runnable {
	Thread t;
	
	JLabel prompt;
	JLabel count;
	JButton start;
	JTextField bpm;
	
	int counter = 1;
	boolean startFlag = false;
	
	// Set all properties of the GUI.
	VisualMetronome() {
		JFrame frame = new JFrame("Visual Metronome");
		frame.setLayout(new FlowLayout());
		frame.setSize(375, 150);
		frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
		
		prompt = new JLabel("Enter BPM and press Start.");
		count = new JLabel("0");
		start = new JButton("Start");
		bpm = new JTextField(3);
		
		count.setFont(new Font(count.getName(), Font.PLAIN, 50));
		count.setBounds(100, 100, 50, 50);
		
		bpm.setActionCommand("BPM");
		bpm.setText("60");
		
		frame.add(prompt);
		frame.add(bpm);
		frame.add(start);
		frame.add(count);
		
		start.addActionListener(this);
		frame.setVisible(true);
	}
	
	// Handles Start/Stop button presses.
	public void actionPerformed(ActionEvent ae) {
		if(ae.getActionCommand().equals("Start") || 
				ae.getActionCommand().equals("Stop")) {
			if(!startFlag) {
				// Set and run metronome count.
				counter = 1;
				t = new Thread(this);
				
				startFlag = true;
				start.setText("Stop");
				t.start();
			} else {
				// Stop and terminate metronome count.
				startFlag = false;
				start.setText("Start");
				t = null;
			}
		}
	}
	
	// Run the count on Thread t.
	@Override
	public void run() {
		while(startFlag) {
			
			// Handles count delay.
			try {
				Thread.sleep(1000 / (Integer.valueOf(bpm.getText()) / 60));
			} catch(InterruptedException e) {
				// ... 
			} catch(NumberFormatException|ArithmeticException e) {
				bpm.setText("60");
			}
			
			// Stops count immediately after Stop button has been pushed.
			if(startFlag) {

				if(counter <= 4) {
					count.setText(String.valueOf(counter++));
				} else {
					counter = 1;
					count.setText(String.valueOf(counter++));
				}
				
			}
		}
	}
	
	public static void main(String args[]) {
		SwingUtilities.invokeLater(new Runnable() {
			public void run() {
				new VisualMetronome();
			}
		});
	}

}