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Example with Java 8 Lamdbam executors and futures
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package lamdbastuff; | |
import java.util.ArrayList; | |
import java.util.Iterator; | |
import java.util.List; | |
import java.util.concurrent.Callable; | |
import java.util.concurrent.ExecutorService; | |
import java.util.concurrent.Executors; | |
import java.util.concurrent.Future; | |
import java.util.concurrent.Semaphore; | |
import java.util.concurrent.ThreadLocalRandom; | |
import java.util.concurrent.TimeUnit; | |
import java.util.stream.IntStream; | |
public class Lamdbastuff { | |
static int failed; | |
static boolean debug = false; | |
static Callable<String> longRunningTask(Semaphore s, int i) { | |
return () -> { | |
final long start = System.currentTimeMillis(); | |
boolean permit = false; | |
try { | |
permit = s.tryAcquire(350, TimeUnit.MILLISECONDS); | |
TimeUnit.MILLISECONDS.sleep(ThreadLocalRandom.current().nextInt(10, 25)); | |
if (permit) { | |
TimeUnit.MILLISECONDS.sleep(ThreadLocalRandom.current().nextInt(50, 250)); | |
} else { | |
failed++; | |
} | |
} catch (InterruptedException e) { | |
throw new IllegalStateException(e); | |
} finally { | |
if (permit) { | |
s.release(); | |
} | |
} | |
return "Task " + i + (permit ? " was executed and took " : " was NOT executed but took ") + (System.currentTimeMillis() - start) + " msec"; | |
}; | |
} | |
public static void main(String args[]) throws Exception { | |
ExecutorService executor = Executors.newFixedThreadPool(10); | |
Semaphore semaphore = new Semaphore(3); | |
final List<Future<String>> fut = new ArrayList<>(); | |
IntStream.range(0, 10).forEach(i -> fut.add(executor.submit(longRunningTask(semaphore, i)))); | |
while(!fut.isEmpty()) { | |
for(Iterator<Future<String>> it = fut.iterator() ; it.hasNext() ; ) { | |
Future<String> f = it.next(); | |
if(f.isDone()) { | |
System.out.println(f.get()); | |
it.remove(); | |
} | |
} | |
TimeUnit.MILLISECONDS.sleep(100); | |
} | |
System.out.println("failed=" + failed); | |
executor.shutdown(); | |
} | |
} |
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