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Thread Pools - Part II

Thread pools can be also be elastic: they scale with increased demand to run parallel tasks and shrink when said demand diminishes. An example of such thread pool is called a cached thread pool; to demonstrate the difference, we replace the statement that creates the thread pool in the previous example with this one:

import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;
public class Main {
public static void main(String args[]) throws Exception {
final ExecutorService threadPool = Executors.newCachedThreadPool();
final long startTime = System.nanoTime();
for (int i = 0; i < 10; i++) {
threadPool.submit(() ->doWork(startTime));
if (threadPool.awaitTermination(1, TimeUnit.SECONDS)) {
System.out.println("Thread pool terminated gracefully.");
} else {
System.err.println("Thread pool timed out!");
private static void doWork(final long startTime) {
System.out.println("Timestamp: " + (System.nanoTime() - startTime));
try {
} catch (InterruptedException ex) {
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