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Merge pull request ReactiveX#399 from benjchristensen/pull-390-elemen…
…t-at Merge Pull ReactiveX#390 - elementAt
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247
rxjava-core/src/main/java/rx/operators/OperationElementAt.java
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| /** | ||
| * Copyright 2013 Netflix, Inc. | ||
| * | ||
| * 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 rx.operators; | ||
|
|
||
| import static org.junit.Assert.assertTrue; | ||
| import static org.junit.Assert.fail; | ||
| import static org.mockito.Mockito.mock; | ||
| import static org.mockito.Mockito.any; | ||
| import static org.mockito.Mockito.never; | ||
| import static org.mockito.Mockito.times; | ||
| import static org.mockito.Mockito.verify; | ||
|
|
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| import java.util.Iterator; | ||
| import java.util.concurrent.ExecutionException; | ||
| import java.util.concurrent.atomic.AtomicInteger; | ||
|
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| import org.junit.Test; | ||
|
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| import rx.Observable; | ||
| import rx.Observable.OnSubscribeFunc; | ||
| import rx.Observer; | ||
| import rx.Subscription; | ||
|
|
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| /** | ||
| * Returns the element at a specified index in a sequence. | ||
| */ | ||
| public class OperationElementAt { | ||
|
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| /** | ||
| * Returns the element at a specified index in a sequence. | ||
| * | ||
| * @param source | ||
| * Observable sequence to return the element from. | ||
| * @param index | ||
| * The zero-based index of the element to retrieve. | ||
| * | ||
| * @return An observable sequence that produces the element at the specified | ||
| * position in the source sequence. | ||
| * | ||
| * @throws IndexOutOfBoundsException | ||
| * Index is greater than or equal to the number of elements in | ||
| * the source sequence. | ||
| * @throws IndexOutOfBoundsException | ||
| * Index is less than 0. | ||
| */ | ||
| public static <T> OnSubscribeFunc<T> elementAt(Observable<? extends T> source, int index) { | ||
| return new ElementAt<T>(source, index, null, false); | ||
| } | ||
|
|
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| /** | ||
| * Returns the element at a specified index in a sequence or the default | ||
| * value if the index is out of range. | ||
| * | ||
| * @param source | ||
| * Observable sequence to return the element from. | ||
| * @param index | ||
| * The zero-based index of the element to retrieve. | ||
| * @param defaultValue | ||
| * The default value. | ||
| * | ||
| * @return An observable sequence that produces the element at the specified | ||
| * position in the source sequence, or the default value if the | ||
| * index is outside the bounds of the source sequence. | ||
| * | ||
| * @throws IndexOutOfBoundsException | ||
| * Index is less than 0. | ||
| */ | ||
| public static <T> OnSubscribeFunc<T> elementAtOrDefault(Observable<? extends T> source, int index, T defaultValue) { | ||
| return new ElementAt<T>(source, index, defaultValue, true); | ||
| } | ||
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| private static class ElementAt<T> implements OnSubscribeFunc<T> { | ||
|
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| private final Observable<? extends T> source; | ||
| private final int index; | ||
| private final boolean hasDefault; | ||
| private final T defaultValue; | ||
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| private ElementAt(Observable<? extends T> source, int index, | ||
| T defaultValue, boolean hasDefault) { | ||
| this.source = source; | ||
| this.index = index; | ||
| this.defaultValue = defaultValue; | ||
| this.hasDefault = hasDefault; | ||
| } | ||
|
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| @Override | ||
| public Subscription onSubscribe(final Observer<? super T> observer) { | ||
| final SafeObservableSubscription subscription = new SafeObservableSubscription(); | ||
| return subscription.wrap(source.subscribe(new Observer<T>() { | ||
|
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| private AtomicInteger counter = new AtomicInteger(); | ||
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| @Override | ||
| public void onNext(T value) { | ||
| try { | ||
| int currentIndex = counter.getAndIncrement(); | ||
| if (currentIndex == index) { | ||
| observer.onNext(value); | ||
| observer.onCompleted(); | ||
| } else if (currentIndex > index) { | ||
| // this will work if the sequence is asynchronous, | ||
| // it will have no effect on a synchronous observable | ||
| subscription.unsubscribe(); | ||
| } | ||
| } catch (Throwable ex) { | ||
| observer.onError(ex); | ||
| // this will work if the sequence is asynchronous, it | ||
| // will have no effect on a synchronous observable | ||
| subscription.unsubscribe(); | ||
| } | ||
|
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| } | ||
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| @Override | ||
| public void onError(Throwable ex) { | ||
| observer.onError(ex); | ||
| } | ||
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| @Override | ||
| public void onCompleted() { | ||
| if (index < 0) { | ||
| observer.onError(new IndexOutOfBoundsException(index + " is out of bounds")); | ||
| } else if (counter.get() <= index) { | ||
| if (hasDefault) { | ||
| observer.onNext(defaultValue); | ||
| observer.onCompleted(); | ||
| } else { | ||
| observer.onError(new IndexOutOfBoundsException(index + " is out of bounds")); | ||
| } | ||
| } | ||
| } | ||
| })); | ||
| } | ||
| } | ||
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| public static class UnitTest { | ||
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| @Test | ||
| public void testElementAt() { | ||
| Observable<Integer> w = Observable.from(1, 2); | ||
| Observable<Integer> observable = Observable.create(elementAt(w, 1)); | ||
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| @SuppressWarnings("unchecked") | ||
| Observer<Integer> aObserver = mock(Observer.class); | ||
| observable.subscribe(aObserver); | ||
| verify(aObserver, never()).onNext(1); | ||
| verify(aObserver, times(1)).onNext(2); | ||
| verify(aObserver, never()).onError( | ||
| any(Throwable.class)); | ||
| verify(aObserver, times(1)).onCompleted(); | ||
| } | ||
|
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| @Test | ||
| public void testElementAtWithMinusIndex() { | ||
| Observable<Integer> w = Observable.from(1, 2); | ||
| Observable<Integer> observable = Observable | ||
| .create(elementAt(w, -1)); | ||
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| try { | ||
| Iterator<Integer> iter = OperationToIterator | ||
| .toIterator(observable); | ||
| assertTrue(iter.hasNext()); | ||
| iter.next(); | ||
| fail("expect an IndexOutOfBoundsException when index is out of bounds"); | ||
| } catch (IndexOutOfBoundsException e) { | ||
| } | ||
| } | ||
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| @Test | ||
| public void testElementAtWithIndexOutOfBounds() | ||
| throws InterruptedException, ExecutionException { | ||
| Observable<Integer> w = Observable.from(1, 2); | ||
| Observable<Integer> observable = Observable.create(elementAt(w, 2)); | ||
| try { | ||
| Iterator<Integer> iter = OperationToIterator | ||
| .toIterator(observable); | ||
| assertTrue(iter.hasNext()); | ||
| iter.next(); | ||
| fail("expect an IndexOutOfBoundsException when index is out of bounds"); | ||
| } catch (IndexOutOfBoundsException e) { | ||
| } | ||
| } | ||
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| @Test | ||
| public void testElementAtOrDefault() throws InterruptedException, | ||
| ExecutionException { | ||
| Observable<Integer> w = Observable.from(1, 2); | ||
| Observable<Integer> observable = Observable | ||
| .create(elementAtOrDefault(w, 1, 0)); | ||
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| @SuppressWarnings("unchecked") | ||
| Observer<Integer> aObserver = mock(Observer.class); | ||
| observable.subscribe(aObserver); | ||
| verify(aObserver, never()).onNext(1); | ||
| verify(aObserver, times(1)).onNext(2); | ||
| verify(aObserver, never()).onError(any(Throwable.class)); | ||
| verify(aObserver, times(1)).onCompleted(); | ||
| } | ||
|
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| @Test | ||
| public void testElementAtOrDefaultWithIndexOutOfBounds() | ||
| throws InterruptedException, ExecutionException { | ||
| Observable<Integer> w = Observable.from(1, 2); | ||
| Observable<Integer> observable = Observable | ||
| .create(elementAtOrDefault(w, 2, 0)); | ||
|
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| @SuppressWarnings("unchecked") | ||
| Observer<Integer> aObserver = mock(Observer.class); | ||
| observable.subscribe(aObserver); | ||
| verify(aObserver, never()).onNext(1); | ||
| verify(aObserver, never()).onNext(2); | ||
| verify(aObserver, times(1)).onNext(0); | ||
| verify(aObserver, never()).onError(any(Throwable.class)); | ||
| verify(aObserver, times(1)).onCompleted(); | ||
| } | ||
|
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| @Test | ||
| public void testElementAtOrDefaultWithMinusIndex() { | ||
| Observable<Integer> w = Observable.from(1, 2); | ||
| Observable<Integer> observable = Observable | ||
| .create(elementAtOrDefault(w, -1, 0)); | ||
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| try { | ||
| Iterator<Integer> iter = OperationToIterator | ||
| .toIterator(observable); | ||
| assertTrue(iter.hasNext()); | ||
| iter.next(); | ||
| fail("expect an IndexOutOfBoundsException when index is out of bounds"); | ||
| } catch (IndexOutOfBoundsException e) { | ||
| } | ||
| } | ||
| } | ||
| } |