Stateless Akka Prime Example

StatelessPrime.java

package com.lightbend.akka.sample;

import akka.actor.AbstractLoggingActor;
import akka.actor.Props;

import java.util.HashMap;
import java.util.Map;

class StatelessPrime {

    static class IsPrimeActor extends AbstractLoggingActor {

        // Define the actor protocol
        static class IsPrimeRequest {
            long candidate;
            IsPrimeRequest(long candidate){this.candidate = candidate;}
        }

        static class IsPrimeResponse {
            long candidate;
            boolean isPrime;

            IsPrimeResponse(long candidate, boolean isPrime){
                this.candidate = candidate;
                this.isPrime = isPrime;
            }
        }

        public static Props props() {
            return Props.create(IsPrimeActor.class);
        }

        Receive waitingForCandidates(Map<Long, Boolean> knownPrimes) {
            return receiveBuilder()
                .match(IsPrimeRequest.class, r -> {
                    long candidate = r.candidate;
                    Boolean isPrime = knownPrimes.get(candidate);
                    if (isPrime == null) {
                        isPrime = isPrime(candidate);
                    }
                    knownPrimes.put(candidate, isPrime);
                    getSender().tell(new IsPrimeResponse(candidate, isPrime), getSelf());
                    getContext().become(waitingForCandidates(knownPrimes));
                })
                .build();
        }

        @Override
        public Receive createReceive() {
            return waitingForCandidates(new HashMap<Long, Boolean>());
        }

        private boolean isPrime(long n) {
            if (n <= 3) {
                return n > 1;
            } else if (n % 2 == 0 || n % 3 == 0) {
                return false;
            } else {
                for (int i = 5; i * i <= n; i += 6) {
                    if (n % i == 0 || n % (i + 2) == 0) {
                        return false;
                    }
                }
                return true;
            }
        }
    }

}

StatelessPrimeTest.java

package com.lightbend.akka.sample;

import akka.actor.ActorRef;
import akka.actor.ActorSystem;
import akka.testkit.javadsl.TestKit;
import org.junit.AfterClass;
import org.junit.BeforeClass;
import org.junit.Test;

import static org.junit.Assert.assertEquals;

public class StatelessPrimeTest {
  static ActorSystem system;

  @BeforeClass
  public static void setup() {
    system = ActorSystem.create();
  }

  @AfterClass
  public static void teardown() {
    TestKit.shutdownActorSystem(system);
    system = null;
  }

  @Test
  public void testReplyWithSmallCandidates() {
    TestKit probe = new TestKit(system);
    ActorRef primeActor = system.actorOf(StatelessPrime.IsPrimeActor.props());

    primeActor.tell(new StatelessPrime.IsPrimeActor.IsPrimeRequest(42L), probe.getRef());

    StatelessPrime.IsPrimeActor.IsPrimeResponse response = probe.expectMsgClass(StatelessPrime.IsPrimeActor.IsPrimeResponse.class);

    assertEquals(42L, response.candidate);
    assertEquals(false, response.isPrime);
  }

  @Test
  public void testReplyWithMultipleCandidates() {
    TestKit probe = new TestKit(system);
    ActorRef primeActor = system.actorOf(StatelessPrime.IsPrimeActor.props());

    for (long i = 0; i < 10000; i++) {
      primeActor.tell(new StatelessPrime.IsPrimeActor.IsPrimeRequest(i), probe.getRef());

      StatelessPrime.IsPrimeActor.IsPrimeResponse response = probe.expectMsgClass(StatelessPrime.IsPrimeActor.IsPrimeResponse.class);

      assertEquals(i, response.candidate);
    }
  }

}