public void testPutIfAbsent_supportedAbsent() {
    assertNull(
        "putIfAbsent(notPresent, value) should return null", getMap().putIfAbsent(k3(), v3()));
    expectAdded(e3());
  }

  @MapFeature.Require(SUPPORTS_PUT)
  @CollectionSize.Require(absent = ZERO)
  public void testPutIfAbsent_supportedPresent() {
    assertEquals(
        "putIfAbsent(present, value) should return existing value",
        v0(),

  public void testPutIfAbsent_supportedAbsent() {
    assertNull(
        "putIfAbsent(notPresent, value) should return null", getMap().putIfAbsent(k3(), v3()));
    expectAdded(e3());
  }

  @MapFeature.Require(SUPPORTS_PUT)
  @CollectionSize.Require(absent = ZERO)
  public void testPutIfAbsent_supportedPresent() {
    assertEquals(
        "putIfAbsent(present, value) should return existing value",
        v0(),

    assertNull("putIfAbsent(notPresent, value) should return null", putIfAbsent(e3()));
    expectAdded(e3());
  }

  @MapFeature.Require(SUPPORTS_PUT)
  @CollectionSize.Require(absent = ZERO)
  public void testPutIfAbsent_supportedPresent() {
    assertEquals(
        "putIfAbsent(present, value) should return existing value",
        v0(),
        getMap().putIfAbsent(k0(), v3()));
    expectUnchanged();
  }

    assertNull("putIfAbsent(notPresent, value) should return null", putIfAbsent(e3()));
    expectAdded(e3());
  }

  @MapFeature.Require(SUPPORTS_PUT)
  @CollectionSize.Require(absent = ZERO)
  public void testPutIfAbsent_supportedPresent() {
    assertEquals(
        "putIfAbsent(present, value) should return existing value",
        v0(),
        getMap().putIfAbsent(k0(), v3()));
    expectUnchanged();
  }

    // since get returned null, try a putIfAbsent; that fails due to a simulated race
    when(backingMap.putIfAbsent(eq(KEY), isA(AtomicInteger.class))).thenReturn(existingZero);
    // since the putIfAbsent returned a zero, we'll try to replace...
    when(backingMap.replace(eq(KEY), eq(existingZero), isA(AtomicInteger.class))).thenReturn(false);
    // ...and then putIfAbsent. Simulate failure on both

        }

        // Calculate weight without using computeIfAbsent to avoid recursive update issues
        long weight = calculateWeight(project);

        // Use putIfAbsent to handle concurrent access safely
        Long previousWeight = projectWeights.putIfAbsent(project, weight);
        return previousWeight != null ? previousWeight : weight;
    }

    private Comparator<MavenProject> createComparator() {

    while (true) {
      AtomicInteger existingCounter = safeGet(countMap, element);
      if (existingCounter == null) {
        existingCounter = countMap.putIfAbsent(element, new AtomicInteger(occurrences));
        if (existingCounter == null) {
          return 0;
        }
        // existingCounter != null: fall through to operate against the existing AtomicInteger
      }

  protected ForwardingConcurrentMap() {}

  @Override
  protected abstract ConcurrentMap<K, V> delegate();

  @CanIgnoreReturnValue
  @Override
  public @Nullable V putIfAbsent(K key, V value) {
    return delegate().putIfAbsent(key, value);
  }

  @CanIgnoreReturnValue
  @Override
  public boolean remove(@Nullable Object key, @Nullable Object value) {
    return delegate().remove(key, value);
  }

    }

    private static List<String> visitAll(
            Collection<Vertex> children, Map<Vertex, DfsState> stateMap, List<String> list) {
        for (Vertex v : children) {
            DfsState state = stateMap.putIfAbsent(v, DfsState.VISITING);
            if (state == null) {
                visitAll(v.children, stateMap, list);
                stateMap.put(v, DfsState.VISITED);
                list.add(v.label);
            }
        }

    }
  }

  public void testPutIfAbsent() {
    TestMap map = new TestMap();
    map.put("foo", 1);
    assertEquals(Integer.valueOf(1), map.putIfAbsent("foo", 2));
    assertEquals(Integer.valueOf(1), map.get("foo"));
    assertThat(map.putIfAbsent("bar", 3)).isNull();
    assertEquals(Integer.valueOf(3), map.get("bar"));
  }

  public void testRemove() {
    TestMap map = new TestMap();
    map.put("foo", 1);