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

import java.util.concurrent.Executor;
import java.util.concurrent.PriorityBlockingQueue;
import java.util.concurrent.SynchronousQueue;
import java.util.concurrent.ThreadFactory;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicBoolean;
import java.util.concurrent.atomic.AtomicInteger;
import java.util.concurrent.atomic.AtomicLong;
import java.util.concurrent.atomic.AtomicReference;
import java.util.regex.MatchResult;
import java.util.regex.Pattern;
import junit.framework.TestCase;
/**
 * Unit test for {@link ArbitraryInstances}.
 *
 * @author Ben Yu
 */
public class ArbitraryInstancesTest extends TestCase {
  public void testGet_primitives() {
    assertNull(ArbitraryInstances.get(void.class));
    assertNull(ArbitraryInstances.get(Void.class));
    assertEquals(Boolean.FALSE, ArbitraryInstances.get(boolean.class));
    assertEquals(Boolean.FALSE, ArbitraryInstances.get(Boolean.class));
    assertEquals(Character.valueOf('\0'), ArbitraryInstances.get(char.class));
    assertEquals(Character.valueOf('\0'), ArbitraryInstances.get(Character.class));
    assertEquals(Byte.valueOf((byte) 0), ArbitraryInstances.get(byte.class));
    assertEquals(Byte.valueOf((byte) 0), ArbitraryInstances.get(Byte.class));
    assertEquals(Short.valueOf((short) 0), ArbitraryInstances.get(short.class));
    assertEquals(Short.valueOf((short) 0), ArbitraryInstances.get(Short.class));
    assertEquals(Integer.valueOf(0), ArbitraryInstances.get(int.class));