@ElementTypesAreNonnullByDefault
@GwtCompatible(emulated = true)
public class SuppliersTest extends TestCase {

  static class CountingSupplier implements Supplier<Integer> {
    int calls = 0;

    @Override
    public Integer get() {
      calls++;
      return calls * 10;
    }

    @Override
    public String toString() {
      return "CountingSupplier";
    }
  }

@ElementTypesAreNonnullByDefault
@GwtCompatible(emulated = true)
public class SuppliersTest extends TestCase {

  static class CountingSupplier implements Supplier<Integer> {
    int calls = 0;

    @Override
    public Integer get() {
      calls++;
      return calls * 10;
    }

    @Override
    public String toString() {
      return "CountingSupplier";
    }
  }

  /**
   * The map does not throw {@code NullPointerException} on calls such as {@code containsKey(null)},
   * {@code get(null)}, {@code keySet().contains(null)} or {@code remove(null)}.
   */
  ALLOWS_NULL_KEY_QUERIES,
  ALLOWS_NULL_KEYS(ALLOWS_NULL_KEY_QUERIES),
  /**
   * The map does not throw {@code NullPointerException} on calls such as {@code

   * as {@code execute} and {@code invokeAny}, are implemented in terms of calls to {@code
   * delegate.execute}. All other methods are forwarded unchanged to the delegate. This implies that
   * the returned {@code ListeningExecutorService} never calls the delegate's {@code submit}, {@code
   * invokeAll}, and {@code invokeAny} methods, so any special handling of tasks must be implemented

     * immediately fails with the same exception:
     *
     * Thread1: calls setException(), which returns true, context switch before it can CAS
     * seenExceptions to its exception
     *
     * Thread2: calls setException(), which returns false, CASes seenExceptions to its exception,

       * class with a manual reference back to the "containing" class.)
       *
       * This has the nice-ish side effect of limiting reentrancy: run() calls
       * timeoutFuture.setException() calls run(). That reentrancy would already be harmless, since
       * timeoutFuture can be set (and delegate cancelled) only once. (And "set only once" is

import java.util.List;
import java.util.concurrent.atomic.AtomicInteger;
import org.checkerframework.checker.nullness.qual.Nullable;

/**
 * Tester to ensure forwarding wrapper works by delegating calls to the corresponding method with
 * the same parameters forwarded and return value forwarded back or exception propagated as is.
 *
 * <p>For example:
 *
 * <pre>{@code

import java.util.List;
import java.util.concurrent.atomic.AtomicInteger;
import org.checkerframework.checker.nullness.qual.Nullable;

/**
 * Tester to ensure forwarding wrapper works by delegating calls to the corresponding method with
 * the same parameters forwarded and return value forwarded back or exception propagated as is.
 *
 * <p>For example:
 *
 * <pre>{@code

    throw new UnsupportedOperationException();
  }

  /**
   * Not supported. <b>You are attempting to create a set that may contain a non-{@code Comparable}
   * element.</b> Proper calls will resolve to the version in {@code ImmutableSortedSet}, not this
   * dummy version.
   *
   * @throws UnsupportedOperationException always
   * @deprecated <b>Pass a parameter of type {@code Comparable} to use {@link

@SuppressWarnings("rawtypes") // maybe avoidable if we rework the whole package?
@GwtCompatible
public enum CollectionFeature implements Feature<Collection> {
  /**
   * The collection must not throw {@code NullPointerException} on calls such as {@code
   * contains(null)} or {@code remove(null)}, but instead must return a simple {@code false}.
   */
  ALLOWS_NULL_QUERIES,
  ALLOWS_NULL_VALUES(ALLOWS_NULL_QUERIES),

  /**