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

assertEquals(Integer.valueOf(0), ArbitraryInstances.get(Integer.class));
    assertEquals(Long.valueOf(0), ArbitraryInstances.get(long.class));
    assertEquals(Long.valueOf(0), ArbitraryInstances.get(Long.class));
    assertEquals(Float.valueOf(0), ArbitraryInstances.get(float.class));
    assertEquals(Float.valueOf(0), ArbitraryInstances.get(Float.class));
    assertEquals(Double.valueOf(0), ArbitraryInstances.get(double.class));
    assertEquals(Double.valueOf(0), ArbitraryInstances.get(Double.class));
    assertEquals(UnsignedInteger.ZERO, ArbitraryInstances.get(UnsignedInteger.class));
    assertEquals(UnsignedLong.ZERO, ArbitraryInstances.get(UnsignedLong.class));
    assertEquals(0, ArbitraryInstances.get(BigDecimal.class).intValue());
    assertEquals(0, ArbitraryInstances.get(BigInteger.class).intValue());
    assertEquals("", ArbitraryInstances.get(String.class));
    assertEquals("", ArbitraryInstances.get(CharSequence.class));
    assertEquals(TimeUnit.SECONDS, ArbitraryInstances.get(TimeUnit.class));
    assertNotNull(ArbitraryInstances.get(Object.class));
    assertEquals(0, ArbitraryInstances.get(Number.class));
    assertEquals(Charsets.UTF_8, ArbitraryInstances.get(Charset.class));
    assertEquals(Optional.empty(), ArbitraryInstances.get(Optional.class));
    assertEquals(OptionalInt.empty(), ArbitraryInstances.get(OptionalInt.class));
    assertEquals(OptionalLong.empty(), ArbitraryInstances.get(OptionalLong.class));
    assertEquals(OptionalDouble.empty(), ArbitraryInstances.get(OptionalDouble.class));
    assertNotNull(ArbitraryInstances.get(UUID.class));
  }
  public void testGet_collections() {
    assertEquals(ImmutableSet.of().iterator(), ArbitraryInstances.get(Iterator.class));
    assertFalse(ArbitraryInstances.get(PeekingIterator.class).hasNext());
    assertFalse(ArbitraryInstances.get(ListIterator.class).hasNext());
    assertEquals(ImmutableSet.of(), ArbitraryInstances.get(Iterable.class));
    assertEquals(ImmutableSet.of(), ArbitraryInstances.get(Set.class));
    assertEquals(ImmutableSet.of(), ArbitraryInstances.get(ImmutableSet.class));