Please get checker-qual and error_prone_annotations to agree with caffeine...update your check-qual dependency to 2.6.0 and your error_prone_annotations dependency to 2.3.3, please.

    Require upper bound dependencies error for org.checkerframework:checker-qua>
        +-com.google.guava:guava:27.1-jre (managed) <-- com.google.guava:guava:>
          +-org.checkerframework:checker-qual:2.5.2
    and
        +-com.github.ben-manes.caffeine:caffeine:2.7.0
          +-org.checkerframework:checker-qual:2.6.0

    Require upper bound dependencies error for com.google.errorprone:error_pron>
        +-com.google.guava:guava:27.1-jre (managed) <-- com.google.guava:guava:>
          +-com.google.errorprone:error_prone_annotations:2.2.0
    and
        +-com.github.ben-manes.caffeine:caffeine:2.7.0
          +-com.google.errorprone:error_prone_annotations:2.3.3

ArbitraryInstances.get(Random.class).nextInt());
  }
  public void testGet_concurrent() {
    assertTrue(ArbitraryInstances.get(BlockingDeque.class).isEmpty());
    assertTrue(ArbitraryInstances.get(BlockingQueue.class).isEmpty());
    assertTrue(ArbitraryInstances.get(DelayQueue.class).isEmpty());
    assertTrue(ArbitraryInstances.get(SynchronousQueue.class).isEmpty());
    assertTrue(ArbitraryInstances.get(PriorityBlockingQueue.class).isEmpty());
    assertTrue(ArbitraryInstances.get(ConcurrentMap.class).isEmpty());
    assertTrue(ArbitraryInstances.get(ConcurrentNavigableMap.class).isEmpty());
    ArbitraryInstances.get(Executor.class).execute(ArbitraryInstances.get(Runnable.class));
    assertNotNull(ArbitraryInstances.get(ThreadFactory.class));
    assertFreshInstanceReturned(
        BlockingQueue.class,
        BlockingDeque.class,
        PriorityBlockingQueue.class,
        DelayQueue.class,
        SynchronousQueue.class,
        ConcurrentMap.class,
        ConcurrentNavigableMap.class,
        AtomicReference.class,
        AtomicBoolean.class,
        AtomicInteger.class,
        AtomicLong.class,
        AtomicDouble.class);
  }
  @SuppressWarnings("unchecked") 
  public void testGet_functors() {
    assertEquals(0, ArbitraryInstances.get(Comparator.class).compare("abc", 123));
    assertTrue(ArbitraryInstances.get(Predicate.class).apply("abc"));