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

}
  public void testGet_enum() {
    assertNull(ArbitraryInstances.get(EmptyEnum.class));
    assertEquals(Direction.UP, ArbitraryInstances.get(Direction.class));
  }
  public void testGet_interface() {
    assertNull(ArbitraryInstances.get(SomeInterface.class));
  }
  public void testGet_runnable() {
    ArbitraryInstances.get(Runnable.class).run();
  }
  public void testGet_class() {
    assertSame(SomeAbstractClass.INSTANCE, ArbitraryInstances.get(SomeAbstractClass.class));
    assertSame(
        WithPrivateConstructor.INSTANCE, ArbitraryInstances.get(WithPrivateConstructor.class));
    assertNull(ArbitraryInstances.get(NoDefaultConstructor.class));
    assertSame(
        WithExceptionalConstructor.INSTANCE,
        ArbitraryInstances.get(WithExceptionalConstructor.class));
    assertNull(ArbitraryInstances.get(NonPublicClass.class));
  }
  public void testGet_mutable() {
    assertEquals(0, ArbitraryInstances.get(ArrayList.class).size());
    assertEquals(0, ArbitraryInstances.get(HashMap.class).size());
    assertThat(ArbitraryInstances.get(Appendable.class).toString()).isEmpty();
    assertThat(ArbitraryInstances.get(StringBuilder.class).toString()).isEmpty();
    assertThat(ArbitraryInstances.get(StringBuffer.class).toString()).isEmpty();
    assertFreshInstanceReturned(
        ArrayList.class,
        HashMap.class,