Java tutorial
/* * 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 <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<?></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 <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 <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 <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 {@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 {@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; }