https://source.android.com/ 
/*
 * Copyright (C) 2009 The Android Open Source Project
 *
 * 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 android.accounts;

import java.util.concurrent.TimeUnit;
import java.io.IOException;


A AccountManagerFuture represents the result of an asynchronous AccountManager call. Methods are provided to check if the computation is complete, to wait for its completion, and to retrieve the result of the computation. The result can only be retrieved using method get when the computation has completed, blocking if
necessary until it is ready.  Cancellation is performed by the
cancel method.  Additional methods are provided to
determine if the task completed normally or was cancelled. Once a
computation has completed, the computation cannot be cancelled.
If you would like to use a Future for the sake
of cancellability but not provide a usable result, you can
declare types of the form Future<?> and
return null as a result of the underlying task.

/**
 * A <tt>AccountManagerFuture</tt> represents the result of an asynchronous
 * {@link AccountManager} call.  Methods are provided to check if the computation is
 * complete, to wait for its completion, and to retrieve the result of
 * the computation.  The result can only be retrieved using method
 * <tt>get</tt> when the computation has completed, blocking if
 * necessary until it is ready.  Cancellation is performed by the
 * <tt>cancel</tt> method.  Additional methods are provided to
 * determine if the task completed normally or was cancelled. Once a
 * computation has completed, the computation cannot be cancelled.
 * If you would like to use a <tt>Future</tt> for the sake
 * of cancellability but not provide a usable result, you can
 * declare types of the form <tt>Future&lt;?&gt;</tt> and
 * return <tt>null</tt> as a result of the underlying task.
 */
public interface AccountManagerFuture<V> {
    
Attempts to cancel execution of this task.  This attempt will
fail if the task has already completed, has already been cancelled,
or could not be cancelled for some other reason. If successful,
and this task has not started when cancel is called,
this task should never run.  If the task has already started,
then the mayInterruptIfRunning parameter determines
whether the thread executing this task should be interrupted in
an attempt to stop the task.

After this method returns, subsequent calls to isDone will always return true. Subsequent calls to isCancelled will always return true if this method returned true.

Params:
  • mayInterruptIfRunning – true if the thread executing this
task should be interrupted; otherwise, in-progress tasks are allowed
to complete
Returns:false if the task could not be cancelled,
typically because it has already completed normally;
true otherwise
/**
     * Attempts to cancel execution of this task.  This attempt will
     * fail if the task has already completed, has already been cancelled,
     * or could not be cancelled for some other reason. If successful,
     * and this task has not started when <tt>cancel</tt> is called,
     * this task should never run.  If the task has already started,
     * then the <tt>mayInterruptIfRunning</tt> parameter determines
     * whether the thread executing this task should be interrupted in
     * an attempt to stop the task.
     *
     * <p>After this method returns, subsequent calls to {@link #isDone} will
     * always return <tt>true</tt>.  Subsequent calls to {@link #isCancelled}
     * will always return <tt>true</tt> if this method returned <tt>true</tt>.
     *
     * @param mayInterruptIfRunning <tt>true</tt> if the thread executing this
     * task should be interrupted; otherwise, in-progress tasks are allowed
     * to complete
     * @return <tt>false</tt> if the task could not be cancelled,
     * typically because it has already completed normally;
     * <tt>true</tt> otherwise
     */
    boolean cancel(boolean mayInterruptIfRunning);

    
Returns true if this task was cancelled before it completed
normally.

Returns:true if this task was cancelled before it completed
/**
     * Returns <tt>true</tt> if this task was cancelled before it completed
     * normally.
     *
     * @return <tt>true</tt> if this task was cancelled before it completed
     */
    boolean isCancelled();

    
Returns true if this task completed.
Completion may be due to normal termination, an exception, or
cancellation -- in all of these cases, this method will return
true.

Returns:true if this task completed
/**
     * Returns <tt>true</tt> if this task completed.
     *
     * Completion may be due to normal termination, an exception, or
     * cancellation -- in all of these cases, this method will return
     * <tt>true</tt>.
     *
     * @return <tt>true</tt> if this task completed
     */
    boolean isDone();

    
Accessor for the future result the AccountManagerFuture represents. This call will block until the result is available. In order to check if the result is available without blocking, one may call isDone() and isCancelled(). If the request that generated this result fails or is canceled then an exception will be thrown rather than the call returning normally. 
Throws:
  • OperationCanceledException – if the request was canceled for any
reason (including if it is forbidden
by policy to modify an account (of that type))
  • AuthenticatorException – if there was an error communicating with
the authenticator or if the authenticator returned an invalid response
  • IOException – if the authenticator returned an error response that indicates
that it encountered an IOException while communicating with the authentication server
Returns:the actual result
/**
     * Accessor for the future result the {@link AccountManagerFuture} represents. This
     * call will block until the result is available. In order to check if the result is
     * available without blocking, one may call {@link #isDone()} and  {@link #isCancelled()}.
     * If the request that generated this result fails or is canceled then an exception
     * will be thrown rather than the call returning normally.
     * @return the actual result
     * @throws android.accounts.OperationCanceledException if the request was canceled for any
     * reason (including if it is forbidden
     * by policy to modify an account (of that type))
     * @throws android.accounts.AuthenticatorException if there was an error communicating with
     * the authenticator or if the authenticator returned an invalid response
     * @throws java.io.IOException if the authenticator returned an error response that indicates
     * that it encountered an IOException while communicating with the authentication server
     */
    V getResult() throws OperationCanceledException, IOException, AuthenticatorException;

    
Accessor for the future result the AccountManagerFuture represents. This call will block until the result is available. In order to check if the result is available without blocking, one may call isDone() and isCancelled(). If the request that generated this result fails or is canceled then an exception will be thrown rather than the call returning normally. If a timeout is specified then the request will automatically be canceled if it does not complete in that amount of time. 
Params:
  • timeout – the maximum time to wait
  • unit – the time unit of the timeout argument. This must not be null.
Throws:
  • OperationCanceledException – if the request was canceled for any
reason
  • AuthenticatorException – if there was an error communicating with
the authenticator or if the authenticator returned an invalid response
  • IOException – if the authenticator returned an error response that indicates
that it encountered an IOException while communicating with the authentication server
Returns:the actual result
/**
     * Accessor for the future result the {@link AccountManagerFuture} represents. This
     * call will block until the result is available. In order to check if the result is
     * available without blocking, one may call {@link #isDone()} and  {@link #isCancelled()}.
     * If the request that generated this result fails or is canceled then an exception
     * will be thrown rather than the call returning normally. If a timeout is specified then
     * the request will automatically be canceled if it does not complete in that amount of time.
     * @param timeout the maximum time to wait
     * @param unit the time unit of the timeout argument. This must not be null.
     * @return the actual result
     * @throws android.accounts.OperationCanceledException if the request was canceled for any
     * reason
     * @throws android.accounts.AuthenticatorException if there was an error communicating with
     * the authenticator or if the authenticator returned an invalid response
     * @throws java.io.IOException if the authenticator returned an error response that indicates
     * that it encountered an IOException while communicating with the authentication server
     */
    V getResult(long timeout, TimeUnit unit)
            throws OperationCanceledException, IOException, AuthenticatorException;
}