https://github.com/google/guava/guava: Guava is a suite of core and expanded libraries that include utility classes, google's collections, io classes, and much much more. 
/*
 * Copyright (C) 2008 The Guava Authors
 *
 * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
 * in compliance with the License. You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software distributed under the License
 * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
 * or implied. See the License for the specific language governing permissions and limitations under
 * the License.
 */

package com.google.common.util.concurrent;

import com.google.common.annotations.Beta;
import com.google.common.annotations.GwtCompatible;
import com.google.errorprone.annotations.CanIgnoreReturnValue;
import java.util.concurrent.CancellationException;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.Future;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.TimeoutException;


A CheckedFuture is a ListenableFuture that includes versions of the get methods that can throw a checked exception. This makes it easier to create a future that executes logic which can throw an exception. 
Warning: We recommend against using CheckedFuture in new projects. 
CheckedFuture is difficult to build libraries atop. CheckedFuture ports of methods like Futures.transformAsync have historically had bugs, and some of these bugs are necessary, unavoidable consequences of the CheckedFuture API. Additionally, CheckedFuture encourages users to take exceptions from one thread and rethrow them in another, producing confusing stack traces. 
A common implementation is Futures.immediateCheckedFuture. 
Implementations of this interface must adapt the exceptions thrown by Future#get(): CancellationException, ExecutionException and InterruptedException into the type specified by the X type parameter. 
This interface also extends the ListenableFuture interface to allow listeners to be added. This allows the future to be used as a normal Future or as an asynchronous callback mechanism as needed. This allows multiple callbacks to be registered for a particular task, and the future will guarantee execution of all listeners when the task completes. 
For a simpler alternative to CheckedFuture, consider accessing Future values with Futures.getChecked(). 
Author:Sven Mawson
Since:1.0
Deprecated:CheckedFuture cannot properly support the chained operations that are the primary goal of ListenableFuture. CheckedFuture also encourages users to rethrow exceptions from one thread in another thread, producing misleading stack traces. Additionally, it has a surprising policy about which exceptions to map and which to leave untouched. Guava users who want a CheckedFuture can fork the classes for their own use, possibly specializing them to the particular exception type they use. We recommend that most people use ListenableFuture and perform any exception wrapping themselves. This class is scheduled for removal from Guava in February 2018.
/**
 * A {@code CheckedFuture} is a {@link ListenableFuture} that includes versions of the {@code get}
 * methods that can throw a checked exception. This makes it easier to create a future that executes
 * logic which can throw an exception.
 *
 * <p><b>Warning:</b> We recommend against using {@code CheckedFuture} in new projects. {@code
 * CheckedFuture} is difficult to build libraries atop. {@code CheckedFuture} ports of methods like
 * {@link Futures#transformAsync} have historically had bugs, and some of these bugs are necessary,
 * unavoidable consequences of the {@code CheckedFuture} API. Additionally, {@code CheckedFuture}
 * encourages users to take exceptions from one thread and rethrow them in another, producing
 * confusing stack traces.
 *
 * <p>A common implementation is {@link Futures#immediateCheckedFuture}.
 *
 * <p>Implementations of this interface must adapt the exceptions thrown by {@code Future#get()}:
 * {@link CancellationException}, {@link ExecutionException} and {@link InterruptedException} into
 * the type specified by the {@code X} type parameter.
 *
 * <p>This interface also extends the ListenableFuture interface to allow listeners to be added.
 * This allows the future to be used as a normal {@link Future} or as an asynchronous callback
 * mechanism as needed. This allows multiple callbacks to be registered for a particular task, and
 * the future will guarantee execution of all listeners when the task completes.
 *
 * <p>For a simpler alternative to CheckedFuture, consider accessing Future values with {@link
 * Futures#getChecked(Future, Class) Futures.getChecked()}.
 *
 * @author Sven Mawson
 * @since 1.0
 * @deprecated {@link CheckedFuture} cannot properly support the chained operations that are the
 *     primary goal of {@link ListenableFuture}. {@code CheckedFuture} also encourages users to
 *     rethrow exceptions from one thread in another thread, producing misleading stack traces.
 *     Additionally, it has a surprising policy about which exceptions to map and which to leave
 *     untouched. Guava users who want a {@code CheckedFuture} can fork the classes for their own
 *     use, possibly specializing them to the particular exception type they use. We recommend that
 *     most people use {@code ListenableFuture} and perform any exception wrapping themselves. This
 *     class is scheduled for removal from Guava in February 2018.
 */
@Beta
@CanIgnoreReturnValue
@Deprecated
@GwtCompatible
public interface CheckedFuture<V, X extends Exception> extends ListenableFuture<V> {

  
Exception checking version of Future.get() that will translate InterruptedException, CancellationException and ExecutionException into application-specific exceptions. 
Throws:
  • X – on interruption, cancellation or execution exceptions.
Returns:the result of executing the future.
/**
   * Exception checking version of {@link Future#get()} that will translate {@link
   * InterruptedException}, {@link CancellationException} and {@link ExecutionException} into
   * application-specific exceptions.
   *
   * @return the result of executing the future.
   * @throws X on interruption, cancellation or execution exceptions.
   */
  V checkedGet() throws X;

  
Exception checking version of Future.get(long, TimeUnit) that will translate InterruptedException, CancellationException and ExecutionException into application-specific exceptions. On timeout this method throws a normal TimeoutException. 
Throws:
  • TimeoutException – if retrieving the result timed out.
  • X – on interruption, cancellation or execution exceptions.
Returns:the result of executing the future.
/**
   * Exception checking version of {@link Future#get(long, TimeUnit)} that will translate {@link
   * InterruptedException}, {@link CancellationException} and {@link ExecutionException} into
   * application-specific exceptions. On timeout this method throws a normal {@link
   * TimeoutException}.
   *
   * @return the result of executing the future.
   * @throws TimeoutException if retrieving the result timed out.
   * @throws X on interruption, cancellation or execution exceptions.
   */
  V checkedGet(long timeout, TimeUnit unit) throws TimeoutException, X;
}