// TODO: test whether null is supported (create a Feature)
    /**
     * The elements to be returned by future calls to {@code next()}, with the first at the top of
     * the stack.
     */
    final Stack<E> nextElements = new Stack<>();

    /**
     * The elements to be returned by future calls to {@code previous()}, with the first at the top
     * of the stack.
     */

    /**
     * Contains the most recently submitted {@code Future}, which may be cancelled or updated,
     * always under a lock.
     */
    private static final class SupplantableFuture implements Cancellable {
      private final ReentrantLock lock;

      @GuardedBy("lock")
      private Future<@Nullable Void> currentFuture;

      SupplantableFuture(ReentrantLock lock, Future<@Nullable Void> currentFuture) {
        this.lock = lock;

    private final ListenableFuture<@Nullable Void> future;
    private boolean called = false;

    private TestCallable(ListenableFuture<@Nullable Void> future) {
      this.future = future;
    }

    @Override
    public ListenableFuture<@Nullable Void> call() throws Exception {
      called = true;
      return future;
    }
  }

    assertAssignable(
        TypeToken.of(new TypeCapture<L>() {}.capture()),
        TypeToken.of(new TypeCapture<L>() {}.capture()));
    assertNotAssignable(
        TypeToken.of(new TypeCapture<R>() {}.capture()),
        TypeToken.of(new TypeCapture<L>() {}.capture()));
    assertAssignable(TypeToken.of(new TypeCapture<L>() {}.capture()), new TypeToken<List<R>>() {});
  }

  public void testisSupertypeOf_resolved() {

  /**
   * Retrieves the result of a {@code Future} known to be done but uses the {@code get(long,
   * TimeUnit)} overload in order to test that method.
   */
  static <V extends @Nullable Object> V getDoneFromTimeoutOverload(Future<V> future)
      throws ExecutionException {
    checkState(future.isDone(), "Future was expected to be done: %s", future);
    try {
      return getUninterruptibly(future, 0, SECONDS);
    } catch (TimeoutException e) {

  public boolean setException(Throwable throwable) {
    return super.setException(throwable);
  }

  @CanIgnoreReturnValue
  @Override
  public boolean setFuture(ListenableFuture<? extends V> future) {
    return super.setFuture(future);
  }

  private SettableFuture() {}

 * specific language governing permissions and limitations
 * under the License.
 */
package org.apache.maven.api.feature;

import java.util.Map;

import org.apache.maven.api.Constants;
import org.apache.maven.api.annotations.Nullable;

/**
 * Centralized class for Maven Core feature information.
 * Features configured are supposed to be final in a given maven session.
 *
 * @since 4.0.0
 */

            taskDone = true;
            return taskDone;
          }
        };
    List<Future<Boolean>> futureList = executor.invokeAll(ImmutableList.of(task), 10, MILLISECONDS);
    Future<Boolean> future = futureList.get(0);
    assertFalse(taskDone);
    assertTrue(future.isDone());
    assertThrows(CancellationException.class, () -> future.get());
  }

            taskDone = true;
            return taskDone;
          }
        };
    List<Future<Boolean>> futureList = executor.invokeAll(ImmutableList.of(task), 10, MILLISECONDS);
    Future<Boolean> future = futureList.get(0);
    assertFalse(taskDone);
    assertTrue(future.isDone());
    assertThrows(CancellationException.class, () -> future.get());
  }

 * specific language governing permissions and limitations
 * under the License.
 */

/**
 * Provides feature flag management and configuration capabilities for Maven core functionality.
 *
 * @since 4.0.0
 */