*/
public abstract class Request<T extends Response> {
    /**
     * Constructs a new request.
     */
    public Request() {
        // nothing
    }

    /**
     * Executes the request.
     * @param client The OpenSearch client.
     * @return A Promise that will be resolved with the response or rejected with an error.
     */
    public Deferred<T>.Promise execute(final Client client) {

 */
@Deprecated(since = "4.0.0")
public class ToolchainsBuildingException extends Exception {

    private final List<Problem> problems;

    /**
     * Creates a new exception with the specified problems.
     *
     * @param problems The problems that cause this exception, must not be {@code null}.
     */
    public ToolchainsBuildingException(List<Problem> problems) {

   * result of a <i>future</i> call to {@code next()}.
   */
  protected abstract @Nullable T computeNext(T previous);

  @Override
  public final boolean hasNext() {
    return nextOrNull != null;
  }

  @Override
  public final T next() {
    if (nextOrNull == null) {
      throw new NoSuchElementException();
    }
    T oldNext = nextOrNull;
    nextOrNull = computeNext(oldNext);

 * 3: "Enforce the singleton property with a private constructor or an enum type". For example:
 *
 * {@snippet :
 * public enum PersonFunnel implements Funnel<Person> {
 *   INSTANCE;
 *   public void funnel(Person person, PrimitiveSink into) {
 *     into.putUnencodedChars(person.getFirstName())
 *         .putUnencodedChars(person.getLastName())
 *         .putInt(person.getAge());

  }

  @Override
  @ParametricNullness
  public final T next() {
    if (!hasNext()) {
      throw new NoSuchElementException();
    }
    state = State.NOT_READY;
    // Safe because hasNext() ensures that tryToComputeNext() has put a T into `next`.
    T result = uncheckedCastNullableTToT(next);
    next = null;
    return result;
  }

  @Override
  public final void remove() {

// it under the terms of the GNU Affero General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// This program is distributed in the hope that it will be useful
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU Affero General Public License for more details.
//

// it under the terms of the GNU Affero General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// This program is distributed in the hope that it will be useful
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU Affero General Public License for more details.
//

// it under the terms of the GNU Affero General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// This program is distributed in the hope that it will be useful
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU Affero General Public License for more details.
//

// it under the terms of the GNU Affero General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// This program is distributed in the hope that it will be useful
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU Affero General Public License for more details.
//

// it under the terms of the GNU Affero General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// This program is distributed in the hope that it will be useful
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU Affero General Public License for more details.
//