Pure java impl of problem described at http://www.bestinclass.dk/index.clj/2009/09/scala-vs-clojure-round-2-concurrency.html

Barber.java

import java.util.UUID;
import java.util.concurrent.LinkedBlockingQueue;

public class Barber {
	private final static int MaxSeats = 3;

	public static void main(String[] args) throws InterruptedException {
		final LinkedBlockingQueue<String> q = new LinkedBlockingQueue<String>(
				MaxSeats);
		// Barber thread
		new Thread(new Runnable() {
			@Override
			public void run() {
				while (true) {
					try {
						String cust = q.take();
						System.out.println("Barber is cutting " + cust
								+ "'s hair.");
						Thread.sleep((long) (100 + Math.random() * 1000));
					} catch (InterruptedException e) {
						break;
					}
				}
			}
		}) {
		}.start();
		while (true) {
			final String customerName = "Customer " + UUID.randomUUID();
			// Customer threads
			new Thread(new Runnable() {
				@Override
				public void run() {
					System.out.println(customerName
							+ (q.offer(customerName) ? " took a seat."
									: " gave up and walked away."));
				}
			}).start();
			Thread.sleep((long) (100 + Math.random() * 1000));
		}
	}
}