Throw NoSuchElementException in the first, last and single operators when the Observable is empty

Author: zsxwing

language-adaptors/rxjava-scala/src/main/scala/rx/lang/scala/Observable.scala

@@ -1950,12 +1950,12 @@ trait Observable[+T]
 
   /**
    * Returns an Observable that emits only the very first item emitted by the source Observable, or raises an
-   * `IllegalArgumentException` if the source Observable is empty.
+   * `NoSuchElementException` if the source Observable is empty.
    * <p>
    * <img width="640" src="https://raw.github.com/wiki/Netflix/RxJava/images/rx-operators/first.png">
    * 
    * @return an Observable that emits only the very first item emitted by the source Observable, or raises an
-   *         `IllegalArgumentException` if the source Observable is empty
+   *         `NoSuchElementException` if the source Observable is empty
    * @see <a href="https://github.com/Netflix/RxJava/wiki/Filtering-Observables#wiki-first">RxJava Wiki: first()</a>
    * @see "MSDN: Observable.firstAsync()"
    */
@@ -1965,12 +1965,12 @@ trait Observable[+T]
 
   /**
    * Returns an Observable that emits only the very first item emitted by the source Observable, or raises an
-   * `IllegalArgumentException` if the source Observable is empty.
+   * `NoSuchElementException` if the source Observable is empty.
    * <p>
    * <img width="640" src="https://raw.github.com/wiki/Netflix/RxJava/images/rx-operators/first.png">
    * 
    * @return an Observable that emits only the very first item emitted by the source Observable, or raises an
-   *         `IllegalArgumentException` if the source Observable is empty
+   *         `NoSuchElementException` if the source Observable is empty
    * @see <a href="https://github.com/Netflix/RxJava/wiki/Filtering-Observables#wiki-first">RxJava Wiki: first()</a>
    * @see "MSDN: Observable.firstAsync()"
    * @see [[Observable.first]]
@@ -1979,7 +1979,7 @@ trait Observable[+T]
 
   /**
    * Returns an Observable that emits the last item emitted by the source Observable or notifies observers of
-   * an `IllegalArgumentException` if the source Observable is empty.
+   * an `NoSuchElementException` if the source Observable is empty.
    * 
    * <img width="640" src="https://raw.github.com/wiki/Netflix/RxJava/images/rx-operators/last.png">
    * 
@@ -1994,12 +1994,12 @@ trait Observable[+T]
 
   /**
    * If the source Observable completes after emitting a single item, return an Observable that emits that
-   * item. If the source Observable emits more than one item or no items, throw an `IllegalArgumentException`.
+   * item. If the source Observable emits more than one item or no items, throw an `NoSuchElementException`.
    * 
    * <img width="640" src="https://raw.github.com/wiki/Netflix/RxJava/images/rx-operators/single.png">
    * 
    * @return an Observable that emits the single item emitted by the source Observable
-   * @throws IllegalArgumentException
+   * @throws NoSuchElementException
    *             if the source emits more than one item or no items
    * @see <a href="https://github.com/Netflix/RxJava/wiki/Observable-Utility-Operators#wiki-single-and-singleordefault">RxJava Wiki: single()</a>
    * @see "MSDN: Observable.singleAsync()"

language-adaptors/rxjava-scala/src/main/scala/rx/lang/scala/observables/BlockingObservable.scala

@@ -55,12 +55,12 @@ class BlockingObservable[+T] private[scala] (val asJava: rx.observables.Blocking
 
   /**
    * Returns the last item emitted by a specified [[Observable]], or
-   * throws `IllegalArgumentException` if it emits no items.
+   * throws `NoSuchElementException` if it emits no items.
    * 
    * <img width="640" src="https://github.com/Netflix/RxJava/wiki/images/rx-operators/B.last.png">
    * 
    * @return the last item emitted by the source [[Observable]]
-   * @throws IllegalArgumentException
+   * @throws NoSuchElementException
    *             if source contains no elements
    * @see <a href="https://github.com/Netflix/RxJava/wiki/Blocking-Observable-Operators#last-and-lastordefault">RxJava Wiki: last()</a>
    * @see <a href="http://msdn.microsoft.com/en-us/library/system.reactive.linq.observable.last.aspx">MSDN: Observable.Last</a>
@@ -71,10 +71,10 @@ class BlockingObservable[+T] private[scala] (val asJava: rx.observables.Blocking
 
   /**
    * Returns the first item emitted by a specified [[Observable]], or
-   * `IllegalArgumentException` if source contains no elements.
+   * `NoSuchElementException` if source contains no elements.
    * 
    * @return the first item emitted by the source [[Observable]]
-   * @throws IllegalArgumentException
+   * @throws NoSuchElementException
    *             if source contains no elements
    * @see <a href="https://github.com/Netflix/RxJava/wiki/Blocking-Observable-Operators#first-and-firstordefault">RxJava Wiki: first()</a>
    * @see <a href="http://msdn.microsoft.com/en-us/library/hh229177.aspx">MSDN: Observable.First</a>
@@ -85,10 +85,10 @@ class BlockingObservable[+T] private[scala] (val asJava: rx.observables.Blocking
 
   /**
    * Returns the first item emitted by a specified [[Observable]], or
-   * `IllegalArgumentException` if source contains no elements.
+   * `NoSuchElementException` if source contains no elements.
    * 
    * @return the first item emitted by the source [[Observable]]
-   * @throws IllegalArgumentException
+   * @throws NoSuchElementException
    *             if source contains no elements
    * @see <a href="https://github.com/Netflix/RxJava/wiki/Blocking-Observable-Operators#first-and-firstordefault">RxJava Wiki: first()</a>
    * @see <a href="http://msdn.microsoft.com/en-us/library/hh229177.aspx">MSDN: Observable.First</a>

rxjava-core/src/main/java/rx/Observable.java

@@ -4545,12 +4545,12 @@ public final Observable<T> finallyDo(Action0 action) {
 
     /**
      * Returns an Observable that emits only the very first item emitted by the source Observable, or raises an
-     * {@code IllegalArgumentException} if the source Observable is empty.
+     * {@code NoSuchElementException} if the source Observable is empty.
      * <p>
      * <img width="640" src="https://raw.github.com/wiki/Netflix/RxJava/images/rx-operators/first.png">
      * 
      * @return an Observable that emits only the very first item emitted by the source Observable, or raises an
-     *         {@code IllegalArgumentException} if the source Observable is empty
+     *         {@code NoSuchElementException} if the source Observable is empty
      * @see <a href="https://github.com/Netflix/RxJava/wiki/Filtering-Observables#wiki-first">RxJava Wiki: first()</a>
      * @see "MSDN: Observable.firstAsync()"
      */
@@ -4560,14 +4560,14 @@ public final Observable<T> first() {
 
     /**
      * Returns an Observable that emits only the very first item emitted by the source Observable that satisfies
-     * a specified condition, or raises an {@code IllegalArgumentException} if no such items are emitted.
+     * a specified condition, or raises an {@code NoSuchElementException} if no such items are emitted.
      * <p>
      * <img width="640" src="https://raw.github.com/wiki/Netflix/RxJava/images/rx-operators/firstN.png">
      * 
      * @param predicate
      *            the condition that an item emitted by the source Observable has to satisfy
      * @return an Observable that emits only the very first item emitted by the source Observable that satisfies
-     *         the {@code predicate}, or raises an {@code IllegalArgumentException} if no such items are emitted
+     *         the {@code predicate}, or raises an {@code NoSuchElementException} if no such items are emitted
      * @see <a href="https://github.com/Netflix/RxJava/wiki/Filtering-Observables#wiki-first">RxJava Wiki: first()</a>
      * @see "MSDN: Observable.firstAsync()"
      */
@@ -4778,7 +4778,7 @@ public final <TRight, TLeftDuration, TRightDuration, R> Observable<R> join(Obser
 
     /**
      * Returns an Observable that emits the last item emitted by the source Observable or notifies observers of
-     * an {@code IllegalArgumentException} if the source Observable is empty.
+     * an {@code NoSuchElementException} if the source Observable is empty.
      * <p>
      * <img width="640" src="https://raw.github.com/wiki/Netflix/RxJava/images/rx-operators/last.png">
      * 
@@ -4793,14 +4793,14 @@ public final Observable<T> last() {
 
     /**
      * Returns an Observable that emits only the last item emitted by the source Observable that satisfies a
-     * given condition, or an {@code IllegalArgumentException} if no such items are emitted.
+     * given condition, or an {@code NoSuchElementException} if no such items are emitted.
      * <p>
      * <img width="640" src="https://raw.github.com/wiki/Netflix/RxJava/images/rx-operators/last.p.png">
      * 
      * @param predicate
      *            the condition any source emitted item has to satisfy
      * @return an Observable that emits only the last item satisfying the given condition from the source, or an
-     *         {@code IllegalArgumentException} if no such items are emitted
+     *         {@code NoSuchElementException} if no such items are emitted
      * @throws IllegalArgumentException
      *             if no items that match the predicate are emitted by the source Observable
      * @see <a href="https://github.com/Netflix/RxJava/wiki/Filtering-Observable-Operators#wiki-last">RxJava Wiki: last()</a>
@@ -6205,13 +6205,15 @@ public final Observable<T> serialize() {
     /**
      * If the source Observable completes after emitting a single item, return an Observable that emits that
      * item. If the source Observable emits more than one item or no items, throw an
-     * {@code IllegalArgumentException}.
+     * {@code NoSuchElementException}.
      * <p>
      * <img width="640" src="https://raw.github.com/wiki/Netflix/RxJava/images/rx-operators/single.png">
      * 
      * @return an Observable that emits the single item emitted by the source Observable
      * @throws IllegalArgumentException
-     *             if the source emits more than one item or no items
+     *             if the source emits more than one item
+     * @throws NoSuchElementException
+     *             if the source emits no items
      * @see <a href="https://github.com/Netflix/RxJava/wiki/Observable-Utility-Operators#wiki-single-and-singleordefault">RxJava Wiki: single()</a>
      * @see "MSDN: Observable.singleAsync()"
      */
@@ -6222,7 +6224,7 @@ public final Observable<T> single() {
     /**
      * If the Observable completes after emitting a single item that matches a specified predicate, return an
      * Observable that emits that item. If the source Observable emits more than one such item or no such items,
-     * throw an {@code IllegalArgumentException}.
+     * throw an {@code NoSuchElementException}.
      * <p>
      * <img width="640" src="https://raw.github.com/wiki/Netflix/RxJava/images/rx-operators/single.p.png">
      * 
@@ -6231,8 +6233,9 @@ public final Observable<T> single() {
      * @return an Observable that emits the single item emitted by the source Observable that matches the
      *         predicate
      * @throws IllegalArgumentException
-     *             if the source Observable emits either more than one item that matches the predicate or no
-     *             items that match the predicate
+     *             if the source Observable emits more than one item that matches the predicate
+     * @throws NoSuchElementException
+     *             if the source Observable emits no item that matches the predicate
      * @see <a href="https://github.com/Netflix/RxJava/wiki/Observable-Utility-Operators#wiki-single-and-singleordefault">RxJava Wiki: single()</a>
      * @see "MSDN: Observable.singleAsync()"
      */

rxjava-core/src/main/java/rx/observables/BlockingObservable.java

@@ -163,10 +163,10 @@ public Iterator<T> getIterator() {
 
     /**
      * Returns the first item emitted by a specified {@link Observable}, or
-     * <code>IllegalArgumentException</code> if source contains no elements.
+     * <code>NoSuchElementException</code> if source contains no elements.
      * 
      * @return the first item emitted by the source {@link Observable}
-     * @throws IllegalArgumentException
+     * @throws NoSuchElementException
      *             if source contains no elements
      * @see <a href="https://github.com/Netflix/RxJava/wiki/Blocking-Observable-Operators#first-and-firstordefault">RxJava Wiki: first()</a>
      * @see <a href="http://msdn.microsoft.com/en-us/library/hh229177.aspx">MSDN: Observable.First</a>
@@ -177,14 +177,14 @@ public T first() {
 
     /**
      * Returns the first item emitted by a specified {@link Observable} that
-     * matches a predicate, or <code>IllegalArgumentException</code> if no such
+     * matches a predicate, or <code>NoSuchElementException</code> if no such
      * item is emitted.
      * 
      * @param predicate
      *            a predicate function to evaluate items emitted by the {@link Observable}
      * @return the first item emitted by the {@link Observable} that matches the
      *         predicate
-     * @throws IllegalArgumentException
+     * @throws NoSuchElementException
      *             if no such items are emitted
      * @see <a href="https://github.com/Netflix/RxJava/wiki/Blocking-Observable-Operators#first-and-firstordefault">RxJava Wiki: first()</a>
      * @see <a href="http://msdn.microsoft.com/en-us/library/hh229739.aspx">MSDN: Observable.First</a>
@@ -227,12 +227,12 @@ public T firstOrDefault(T defaultValue, Func1<? super T, Boolean> predicate) {
 
     /**
      * Returns the last item emitted by a specified {@link Observable}, or
-     * throws <code>IllegalArgumentException</code> if it emits no items.
+     * throws <code>NoSuchElementException</code> if it emits no items.
      * <p>
      * <img width="640" src="https://github.com/Netflix/RxJava/wiki/images/rx-operators/B.last.png">
      * 
      * @return the last item emitted by the source {@link Observable}
-     * @throws IllegalArgumentException
+     * @throws NoSuchElementException
      *             if source contains no elements
      * @see <a href="https://github.com/Netflix/RxJava/wiki/Blocking-Observable-Operators#last-and-lastordefault">RxJava Wiki: last()</a>
      * @see <a href="http://msdn.microsoft.com/en-us/library/system.reactive.linq.observable.last.aspx">MSDN: Observable.Last</a>
@@ -243,7 +243,7 @@ public T last() {
 
     /**
      * Returns the last item emitted by a specified {@link Observable} that
-     * matches a predicate, or throws <code>IllegalArgumentException</code> if
+     * matches a predicate, or throws <code>NoSuchElementException</code> if
      * it emits no such items.
      * <p>
      * <img width="640" src="https://github.com/Netflix/RxJava/wiki/images/rx-operators/B.last.p.png">
@@ -252,7 +252,7 @@ public T last() {
      *            a predicate function to evaluate items emitted by the {@link Observable}
      * @return the last item emitted by the {@link Observable} that matches the
      *         predicate
-     * @throws IllegalArgumentException
+     * @throws NoSuchElementException
      *             if no such items are emitted
      * @see <a href="https://github.com/Netflix/RxJava/wiki/Blocking-Observable-Operators#last-and-lastordefault">RxJava Wiki: last()</a>
      * @see <a href="http://msdn.microsoft.com/en-us/library/system.reactive.linq.observable.last.aspx">MSDN: Observable.Last</a>
@@ -349,7 +349,7 @@ public Iterable<T> latest() {
 
     /**
      * If the {@link Observable} completes after emitting a single item, return
-     * that item, otherwise throw an <code>IllegalArgumentException</code>.
+     * that item, otherwise throw an <code>NoSuchElementException</code>.
      * <p>
      * <img width="640" src="https://github.com/Netflix/RxJava/wiki/images/rx-operators/B.single.png">
      * 
@@ -364,7 +364,7 @@ public T single() {
     /**
      * If the {@link Observable} completes after emitting a single item that
      * matches a given predicate, return that item, otherwise throw an
-     * <code>IllegalArgumentException</code>.
+     * <code>NoSuchElementException</code>.
      * <p>
      * <img width="640" src="https://github.com/Netflix/RxJava/wiki/images/rx-operators/B.single.p.png">
      * 

rxjava-core/src/main/java/rx/operators/OperatorSingle.java

@@ -15,6 +15,8 @@
  */
 package rx.operators;
 
+import java.util.NoSuchElementException;
+
 import rx.Observable.Operator;
 import rx.Subscriber;
 
@@ -73,7 +75,7 @@ public void onCompleted() {
                             subscriber.onNext(defaultValue);
                             subscriber.onCompleted();
                         } else {
-                            subscriber.onError(new IllegalArgumentException("Sequence contains no elements"));
+                            subscriber.onError(new NoSuchElementException("Sequence contains no elements"));
                         }
                     }
                 }

rxjava-core/src/test/java/rx/ObservableTests.java

@@ -23,6 +23,7 @@
 import java.util.Arrays;
 import java.util.LinkedList;
 import java.util.List;
+import java.util.NoSuchElementException;
 import java.util.concurrent.CountDownLatch;
 import java.util.concurrent.TimeUnit;
 import java.util.concurrent.atomic.AtomicInteger;
@@ -204,7 +205,7 @@ public void testFirstOfNone() {
         observable.first().subscribe(w);
         verify(w, never()).onNext(anyInt());
         verify(w, never()).onCompleted();
-        verify(w, times(1)).onError(isA(IllegalArgumentException.class));
+        verify(w, times(1)).onError(isA(NoSuchElementException.class));
     }
 
     @Test
@@ -213,7 +214,7 @@ public void testFirstWithPredicateOfNoneMatchingThePredicate() {
         observable.first(IS_EVEN).subscribe(w);
         verify(w, never()).onNext(anyInt());
         verify(w, never()).onCompleted();
-        verify(w, times(1)).onError(isA(IllegalArgumentException.class));
+        verify(w, times(1)).onError(isA(NoSuchElementException.class));
     }
 
     @Test
@@ -233,9 +234,9 @@ public Integer call(Integer t1, Integer t2) {
     }
 
     /**
-     * A reduce should fail with an IllegalArgumentException if done on an empty Observable.
+     * A reduce should fail with an NoSuchElementException if done on an empty Observable.
      */
-    @Test(expected = IllegalArgumentException.class)
+    @Test(expected = NoSuchElementException.class)
     public void testReduceWithEmptyObservable() {
         Observable<Integer> observable = Observable.range(1, 0);
         observable.reduce(new Func2<Integer, Integer, Integer>() {

rxjava-core/src/test/java/rx/ZipTests.java

@@ -21,6 +21,7 @@
 import java.util.Collections;
 import java.util.HashMap;
 import java.util.Map;
+import java.util.NoSuchElementException;
 
 import org.junit.Test;
 
@@ -100,9 +101,9 @@ public void testCovarianceOfZip() {
      * Occasionally zip may be invoked with 0 observables. Test that we don't block indefinitely instead
      * of immediately invoking zip with 0 argument.
      * 
-     * We now expect an IllegalArgumentException since last() requires at least one value and nothing will be emitted.
+     * We now expect an NoSuchElementException since last() requires at least one value and nothing will be emitted.
      */
-    @Test(expected = IllegalArgumentException.class)
+    @Test(expected = NoSuchElementException.class)
     public void nonBlockingObservable() {
 
         final Object invoked = new Object();