001/*
002 * Copyright (C) 2018 The Guava Authors
003 *
004 * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
005 * in compliance with the License. You may obtain a copy of the License at
006 *
007 * http://www.apache.org/licenses/LICENSE-2.0
008 *
009 * Unless required by applicable law or agreed to in writing, software distributed under the License
010 * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
011 * or implied. See the License for the specific language governing permissions and limitations under
012 * the License.
013 */
014
015package com.google.common.util.concurrent.internal;
016
017
018/**
019 * Static utilities for {@link InternalFutureFailureAccess}. Most users will never need to use this
020 * class.
021 *
022 * <p>This class is GWT-compatible.
023 *
024 * @since {@code com.google.guava:failureaccess:1.0}, which was added as a dependency of Guava in
025 *     Guava 27.0
026 */
027public final class InternalFutures {
028  /**
029   * Usually returns {@code null} but, if the given {@code Future} has failed, may <i>optionally</i>
030   * return the cause of the failure. "Failure" means specifically "completed with an exception"; it
031   * does not include "was cancelled." To be explicit: If this method returns a non-null value,
032   * then:
033   *
034   * <ul>
035   *   <li>{@code isDone()} must return {@code true}
036   *   <li>{@code isCancelled()} must return {@code false}
037   *   <li>{@code get()} must not block, and it must throw an {@code ExecutionException} with the
038   *       return value of this method as its cause
039   * </ul>
040   */
041  public static
042      Throwable tryInternalFastPathGetFailure(InternalFutureFailureAccess future) {
043    return future.tryInternalFastPathGetFailure();
044  }
045
046  private InternalFutures() {}
047}