TestThreadPool.java

 TestThreadPool.java

import java.util.concurrent.*;

import java.util.concurrent.atomic.*;

import static org.junit.Assert.*;

/**

* TestingThreadFactory

* <p/>

* Testing thread pool expansion

*

*/

public class TestThreadPool {

private final TestingThreadFactory threadFactory = new TestingThreadFactory();

public static void main(String...args) throws InterruptedException {

TestThreadPool ttp = new TestThreadPool();

ttp.testPoolExpansion();

}

public void testPoolExpansion() throws InterruptedException {

int MAX_SIZE = 10;

//ExecutorService exec = Executors.newFixedThreadPool(MAX_SIZE);

ExecutorService exec = new ThreadPoolExecutor(

MAX_SIZE, MAX_SIZE, 0L, TimeUnit.MILLISECONDS,

new LinkedBlockingQueue<Runnable>(),

threadFactory // Use the TestingThreadFactory here

);

for (int i = 0; i < 100 * 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);

}

}

This test uses a TestingThreadFactory that maintains a count of created threads, so that test cases can verify the number of threads created during a test run.