OnJava8-Examples/concurrent/IDChecker.java

// 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<List<Integer>> {
    private Supplier<HasID> gen;
    MakeObjects(Supplier<HasID> gen) {
      this.gen = gen;
    }
    @Override public List<Integer> get() {
      return
        Stream.generate(gen)
          .limit(SIZE)
          .map(HasID::getID)
          .collect(Collectors.toList());
    }
  }
  public static void test(Supplier<HasID> gen) {
    CompletableFuture<List<Integer>>
      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();
  }
}