TestThreadPool.java

package ch21concurrent.examples;

import org.testng.annotations.Test;

import java.util.concurrent.*;
import java.util.concurrent.atomic.*;

import static org.testng.Assert.assertEquals;

/**
 * TestingThreadFactory
 * <p/>
 * Testing thread pool expansion
 *
 * @author Brian Goetz and Tim Peierls
 */
@Test
public class TestThreadPool {

    private final TestingThreadFactory threadFactory = new TestingThreadFactory();

    public void testPoolExpansion() throws InterruptedException {
        int MAX_SIZE = 10;
        ExecutorService exec = Executors.newFixedThreadPool(MAX_SIZE);

        for (int i = 0; i < 10 * MAX_SIZE; i++)
            exec.execute(new Runnable() {
                public void run() {
                    try {
                        Thread.sleep(Long.MAX_VALUE);
                    } catch (InterruptedException e) {
                        Thread.currentThread().interrupt();
                    }
                }
            });
        for (int i = 0;
             i < 20 && threadFactory.numCreated.get() < MAX_SIZE;
             i++)
            Thread.sleep(100);
        assertEquals(threadFactory.numCreated.get(), MAX_SIZE);
        exec.shutdownNow();
    }
}

class TestingThreadFactory implements ThreadFactory {
    public final AtomicInteger numCreated = new AtomicInteger();
    private final ThreadFactory factory = Executors.defaultThreadFactory();

    public Thread newThread(Runnable r) {
        numCreated.incrementAndGet();
        return factory.newThread(r);
    }
}