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Implemented the 'elementAt' and 'elementAtOrDefault' operators. see R…
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rxjava-core/src/main/java/rx/operators/OperationElementAt.java
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package rx.operators; | ||
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import static org.junit.Assert.assertTrue; | ||
import static org.junit.Assert.fail; | ||
import static org.mockito.Mockito.mock; | ||
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( | ||
org.mockito.Matchers.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( | ||
org.mockito.Matchers.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( | ||
org.mockito.Matchers.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) { | ||
} | ||
} | ||
} | ||
} |