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Add AsyncPage implementation and docs. Add related tests
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‎gcloud-java-core/src/main/java/com/google/cloud/AsyncPage.java

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import java.util.concurrent.Future;
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/**
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* Interface for asynchronously consuming Google Cloud paginated results.
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*
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* <p>Use {@code AsyncPage} to iterate through all values (also in next pages):
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* <pre> {@code
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* AsyncPage<T> page = ...; // get an AsyncPage<T> instance
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* Iterator<T> iterator = page.iterateAll();
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* while (iterator.hasNext()) {
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* T value = iterator.next();
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* // do something with value
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* }}</pre>
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*
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* <p>Or handle pagination explicitly:
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* <pre> {@code
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* AsyncPage<T> page = ...; // get a AsyncPage<T> instance
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* while (page != null) {
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* for (T value : page.values()) {
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* // do something with value
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* }
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* page = page.nextPage().get();
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* }}</pre>
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*
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* @param <T> the value type that the page holds
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*/
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public interface AsyncPage<T> extends Page<T> {
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/**
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* Returns a {@link Future} object for the next page.
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*/
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Future<AsyncPage<T>> nextPageAsync();
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}

‎gcloud-java-core/src/main/java/com/google/cloud/AsyncPageImpl.java

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/*
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* Copyright 2016 Google Inc. All Rights Reserved.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package com.google.cloud;
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import com.google.common.base.Throwables;
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import com.google.common.util.concurrent.Uninterruptibles;
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import java.io.Serializable;
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import java.util.concurrent.ExecutionException;
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import java.util.concurrent.Future;
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/**
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* Base implementation for asynchronously consuming Google Cloud paginated results.
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*
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* @param <T> the value type that the page holds
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*/
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public class AsyncPageImpl<T> extends PageImpl<T> implements AsyncPage<T> {
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private static final long serialVersionUID = -6009473188630364906L;
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private NextPageFetcher<T> asyncPageFetcher;
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/**
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* Interface for asynchronously fetching the next page of results from the service.
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*
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* @param <T> the value type that the page holds
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*/
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public interface NextPageFetcher<T> extends Serializable {
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Future<AsyncPage<T>> nextPage();
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}
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private static class SyncNextPageFetcher<T> implements PageImpl.NextPageFetcher<T> {
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private static final long serialVersionUID = -4124568632363525351L;
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private NextPageFetcher<T> asyncPageFetcher;
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private SyncNextPageFetcher(NextPageFetcher<T> asyncPageFetcher) {
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this.asyncPageFetcher = asyncPageFetcher;
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}
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@Override
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public Page<T> nextPage() {
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try {
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return asyncPageFetcher != null
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? Uninterruptibles.getUninterruptibly(asyncPageFetcher.nextPage()) : null;
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} catch (ExecutionException ex) {
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throw Throwables.propagate(ex.getCause());
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}
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}
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}
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/**
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* Creates an {@code AsyncPageImpl} object.
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*/
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public AsyncPageImpl(NextPageFetcher<T> asyncPageFetcher, String cursor, Iterable<T> results) {
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super(new SyncNextPageFetcher<T>(asyncPageFetcher), cursor, results);
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this.asyncPageFetcher = asyncPageFetcher;
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}
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@Override
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public Future<AsyncPage<T>> nextPageAsync() {
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if (nextPageCursor() == null || asyncPageFetcher == null) {
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return null;
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}
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return asyncPageFetcher.nextPage();
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}
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}

‎gcloud-java-core/src/test/java/com/google/cloud/AsyncPageImplTest.java

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/*
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* Copyright 2016 Google Inc. All Rights Reserved.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package com.google.cloud;
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import static org.junit.Assert.assertEquals;
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import com.google.common.collect.ImmutableList;
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import com.google.common.util.concurrent.Futures;
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import org.junit.Test;
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import java.util.concurrent.ExecutionException;
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import java.util.concurrent.Future;
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public class AsyncPageImplTest {
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private static final ImmutableList<String> VALUES1 = ImmutableList.of("1", "2");
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private static final ImmutableList<String> VALUES2 = ImmutableList.of("3", "4");
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private static final ImmutableList<String> VALUES3 = ImmutableList.of("5", "6");
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private static final ImmutableList<String> ALL_VALUES = ImmutableList.<String>builder()
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.addAll(VALUES1)
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.addAll(VALUES2)
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.addAll(VALUES3)
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.build();
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private static final ImmutableList<String> SOME_VALUES = ImmutableList.<String>builder()
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.addAll(VALUES2)
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.addAll(VALUES3)
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.build();
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@Test
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public void testPage() {
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final AsyncPageImpl<String> nextResult = new AsyncPageImpl<>(null, "c", VALUES2);
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AsyncPageImpl.NextPageFetcher<String> fetcher = new AsyncPageImpl.NextPageFetcher<String>() {
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private static final long serialVersionUID = 4703765400378593176L;
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@Override
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public Future<AsyncPage<String>> nextPage() {
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return Futures.<AsyncPage<String>>immediateFuture(nextResult);
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}
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};
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AsyncPageImpl<String> result = new AsyncPageImpl<>(fetcher, "c", VALUES1);
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assertEquals(nextResult, result.nextPage());
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assertEquals("c", result.nextPageCursor());
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assertEquals(VALUES1, result.values());
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}
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@Test
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public void testPageAsync() throws ExecutionException, InterruptedException {
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final AsyncPageImpl<String> nextResult = new AsyncPageImpl<>(null, "c", VALUES2);
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AsyncPageImpl.NextPageFetcher<String> fetcher = new AsyncPageImpl.NextPageFetcher<String>() {
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private static final long serialVersionUID = 4703765400378593176L;
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@Override
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public Future<AsyncPage<String>> nextPage() {
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return Futures.<AsyncPage<String>>immediateFuture(nextResult);
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}
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};
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AsyncPageImpl<String> result = new AsyncPageImpl<>(fetcher, "c", VALUES1);
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assertEquals(nextResult, result.nextPageAsync().get());
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assertEquals("c", result.nextPageCursor());
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assertEquals(VALUES1, result.values());
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}
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@Test
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public void testIterateAll() {
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final AsyncPageImpl<String> nextResult2 = new AsyncPageImpl<>(null, "c3", VALUES3);
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AsyncPageImpl.NextPageFetcher<String> fetcher2 = new AsyncPageImpl.NextPageFetcher<String>() {
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private static final long serialVersionUID = -9203621430631884026L;
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@Override
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public Future<AsyncPage<String>> nextPage() {
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return Futures.<AsyncPage<String>>immediateFuture(nextResult2);
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}
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};
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final AsyncPageImpl<String> nextResult1 = new AsyncPageImpl<>(fetcher2, "c2", VALUES2);
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AsyncPageImpl.NextPageFetcher<String> fetcher1 = new AsyncPageImpl.NextPageFetcher<String>() {
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private static final long serialVersionUID = -9203621430631884026L;
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@Override
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public Future<AsyncPage<String>> nextPage() {
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return Futures.<AsyncPage<String>>immediateFuture(nextResult1);
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}
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};
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AsyncPageImpl<String> result = new AsyncPageImpl<>(fetcher1, "c1", VALUES1);
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assertEquals(ALL_VALUES, ImmutableList.copyOf(result.iterateAll()));
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}
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@Test
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public void testAsyncPageAndIterateAll() throws ExecutionException, InterruptedException {
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final AsyncPageImpl<String> nextResult2 = new AsyncPageImpl<>(null, "c3", VALUES3);
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AsyncPageImpl.NextPageFetcher<String> fetcher2 = new AsyncPageImpl.NextPageFetcher<String>() {
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private static final long serialVersionUID = -9203621430631884026L;
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@Override
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public Future<AsyncPage<String>> nextPage() {
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return Futures.<AsyncPage<String>>immediateFuture(nextResult2);
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}
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};
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final AsyncPageImpl<String> nextResult1 = new AsyncPageImpl<>(fetcher2, "c2", VALUES2);
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AsyncPageImpl.NextPageFetcher<String> fetcher1 = new AsyncPageImpl.NextPageFetcher<String>() {
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private static final long serialVersionUID = -9203621430631884026L;
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@Override
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public Future<AsyncPage<String>> nextPage() {
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return Futures.<AsyncPage<String>>immediateFuture(nextResult1);
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}
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};
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AsyncPageImpl<String> result = new AsyncPageImpl<>(fetcher1, "c1", VALUES1);
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assertEquals(nextResult1, result.nextPageAsync().get());
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assertEquals("c1", result.nextPageCursor());
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assertEquals(VALUES1, result.values());
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assertEquals(SOME_VALUES, ImmutableList.copyOf(result.nextPageAsync().get().iterateAll()));
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}
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}

‎gcloud-java-core/src/test/java/com/google/cloud/PageImplTest.java

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public void testPage() {
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final PageImpl<String> nextResult = new PageImpl<>(null, "c", NEXT_VALUES);
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PageImpl.NextPageFetcher<String> fetcher = new PageImpl.NextPageFetcher<String>() {
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private static final long serialVersionUID = -1714571149183431798L;
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@Override
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public PageImpl<String> nextPage() {
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return nextResult;

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