NoVisibility.java example in Java Concurrency in Practice

I've been going through Java Concurrency in Practice and trying to reproduce the examples as I go through.

I found that when trying to illustrate the no visibility problem in chapter 3 the example in the code didn't work for me so I tweaked it a little bit:

	import java.util.Random;
	import java.util.concurrent.*;
	class NoVisibility {
	private boolean ready;
	private int number;
	private final ExecutorService executor;
	private final Random random;
	NoVisibility(ExecutorService executor, Random random) {
	this.executor = executor;
	this.random = random;
	}
	private class Reader implements Callable<Integer> {
	@Override
	public Integer call() throws Exception {
	while (!ready) {
	Thread.yield();
	}
	return number;
	}
	}
	int go() throws ExecutionException, InterruptedException {
	Future<Integer> submission = executor.submit(new Reader());
	int randomNumber = random.nextInt();
	this.number = randomNumber;
	ready = true;
	return submission.get() - randomNumber;
	}
	}

view raw NoVisibility.java hosted with ❤ by GitHub

Here is the test:

	import org.junit.Test;
	import java.util.Random;
	import java.util.concurrent.ExecutionException;
	import java.util.concurrent.ExecutorService;
	import java.util.concurrent.Executors;
	import static org.assertj.core.api.Assertions.assertThat;
	public class NoVisibilityTest {
	private ExecutorService executor = Executors.newSingleThreadExecutor();
	@Test
	public void go() throws ExecutionException, InterruptedException {
	Random random = new Random();
	while (true) {
	assertThat(new NoVisibility(executor, random).go())
	.isEqualTo(0);
	}
	}
	}

view raw NoVisibilityTest.java hosted with ❤ by GitHub

Then after running it for some time:

org.junit.ComparisonFailure:
Expected :0
Actual   :-1822446613

\o/