package com.mzc.common.thread;
 
import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;
 
/**
 * <p class="detail">
 * 功能: 內(nèi)存書(shū)架
 * </p>
 *
 * @author Moore
 * @ClassName Books.
 * @Version V1.0.
 * @date 2019.12.10 14:00:13
 */
public class Books {
 final Map<Integer, String> map = new ConcurrentHashMap<>();
 
 /**
 * <p class="detail">
 * 功能: 存書(shū)，并返回書(shū)的id
 * </p>
 *
 * @param title :
 * @return int
 * @author Moore
 * @date 2019.12.10 14:00:16
 */
 int add(String title) {
 final Integer next = this.map.size() + 1;
 this.map.put(next, title);
 return next;
 }
 
 /**
 * <p class="detail">
 * 功能: 根據(jù)書(shū)的id讀取書(shū)名
 * </p>
 *
 * @param id :
 * @return string
 * @author Moore
 * @date 2019.12.10 14:00:16
 */
 String title(int id) {
 return this.map.get(id);
 }
}

Books books = new Books();
String title = "Elegant Objects";
int id = books.add(title);
assert books.title(id).equals(title);

public class BooksTest {
 @Test
 public void addsAndRetrieves() {
 Books books = new Books();
 String title = "Elegant Objects";
 int id = books.add(title);
 assert books.title(id).equals(title);
 }
}

/**
 * <p class="detail">
 * 功能: 多線程測(cè)試
 * </p>
 *
 * @throws ExecutionException the execution exception
 * @throws InterruptedException the interrupted exception
 * @author Moore
 * @date 2019.12.10 14:16:34
 */
 @Test
 public void addsAndRetrieves2() throws ExecutionException, InterruptedException {
 Books books = new Books();
 int threads = 10;
 ExecutorService service = Executors.newFixedThreadPool(threads);
 Collection<Future<Integer>> futures = new ArrayList<>(threads);
 for (int t = 0; t < threads; ++t) {
  final String title = String.format("Book #%d", t);
  futures.add(service.submit(() -> books.add(title)));
 }
 Set<Integer> ids = new HashSet<>();
 for (Future<Integer> f : futures) {
  ids.add(f.get());
 }
 assertThat(ids.size(), equalTo(threads));
 }

@Test
 public void addsAndRetrieves3() {
  Books books = new Books();
  int threads = 10;
  ExecutorService service = Executors.newFixedThreadPool(threads);
  AtomicBoolean running = new AtomicBoolean();
  AtomicInteger overlaps = new AtomicInteger();
  Collection<Future<Integer>> futures = new ArrayList<>(threads);
  for (int t = 0; t < threads; ++t) {
   final String title = String.format("Book #%d", t);
   futures.add(
     service.submit(
       () -> {
        if (running.get()) {
         overlaps.incrementAndGet();
        }
        running.set(true);
        int id = books.add(title);
        running.set(false);
        return id;
       }
     )
   );
  }
  assertThat(overlaps.get(), greaterThan(0));
 }

@Test
  public void addsAndRetrieves4() throws ExecutionException, InterruptedException {
    Books books = new Books();
    int threads = 10;
    ExecutorService service = Executors.newFixedThreadPool(threads);
    CountDownLatch latch = new CountDownLatch(1);
    AtomicBoolean running = new AtomicBoolean();
    AtomicInteger overlaps = new AtomicInteger();
    Collection<Future<Integer>> futures = new ArrayList<>(threads);
    for (int t = 0; t < threads; ++t) {
      final String title = String.format("Book #%d", t);
      futures.add(
          service.submit(
              () -> {
                latch.await();
                if (running.get()) {
                  overlaps.incrementAndGet();
                }
                running.set(true);
                int id = books.add(title);
                running.set(false);
                return id;
              }
          )
      );
    }
    latch.countDown();
    Set<Integer> ids = new HashSet<>();
    for (Future<Integer> f : futures) {
      ids.add(f.get());
    }
    assertThat(overlaps.get(), greaterThan(0));
  }

@Test
  public void addsAndRetrieves5() {
    Books books = new Books();
    MatcherAssert.assertThat(
        t -> {
          String title = String.format(
              "Book #%d", t.getAndIncrement()
          );
          int id = books.add(title);
          return books.title(id).equals(title);
        },
        new RunsInThreads<>(new AtomicInteger(), 10)
    );
  }

<dependency>
      <groupId>org.llorllale</groupId>
      <artifactId>cactoos-matchers</artifactId>
      <version>0.18</version>
    </dependency>