// concurrent/IDChecker.java // (c)2021 MindView LLC: see Copyright.txt // We make no guarantees that this code is fit for any purpose. // Visit http://OnJava8.com for more book information. import java.util.*; import java.util.function.*; import java.util.stream.*; import java.util.concurrent.*; import com.google.common.collect.Sets; public class IDChecker { public static final int SIZE = 100_000; static class MakeObjects implements Supplier> { private Supplier gen; MakeObjects(Supplier gen) { this.gen = gen; } @Override public List get() { return Stream.generate(gen) .limit(SIZE) .map(HasID::getID) .collect(Collectors.toList()); } } public static void test(Supplier gen) { CompletableFuture> groupA = CompletableFuture .supplyAsync(new MakeObjects(gen)), groupB = CompletableFuture .supplyAsync(new MakeObjects(gen)); groupA.thenAcceptBoth(groupB, (a, b) -> { System.out.println( Sets.intersection( Sets.newHashSet(a), Sets.newHashSet(b)).size()); }).join(); } }