Change Observable methods to return Single, Maybe, or Completable in cases where is it returning a 1 or 0 values.

Author: Mauin

src/main/java/io/reactivex/Maybe.java

@@ -440,7 +440,7 @@ public static <T> Maybe<T> just(T item) {
         ObjectHelper.requireNonNull(item, "item is null");
         return RxJavaPlugins.onAssembly(new MaybeJust<T>(item));
     }
-
+    
     /**
      * Merges an Iterable sequence of MaybeSource instances into a single Flowable sequence,
      * running all MaybeSources at once.
@@ -700,6 +700,33 @@ public static <T> Maybe<T> wrap(MaybeSource<T> source) {
     // Instance methods
     // ------------------------------------------------------------------
 
+    /**
+     * Waits in a blocking fashion until the current Maybe signals a success value (which is returned) or
+     * defaultValue if completed or an exception (which is propagated).
+     * <dl>
+     * <dt><b>Scheduler:</b></dt>
+     * <dd>{@code blockingGet} does not operate by default on a particular {@link Scheduler}.</dd>
+     * </dl>
+     * @return the success value
+     */
+    public T blockingGet() {
+        return MaybeAwait.get(this, null);
+    }
+
+    /**
+     * Waits in a blocking fashion until the current Maybe signals a success value (which is returned) or
+     * defaultValue if completed or an exception (which is propagated).
+     * <dl>
+     * <dt><b>Scheduler:</b></dt>
+     * <dd>{@code blockingGet} does not operate by default on a particular {@link Scheduler}.</dd>
+     * </dl>
+     * @return the success value
+     */
+    public T blockingGet(T defaultValue) {
+        ObjectHelper.requireNonNull(defaultValue, "defaultValue is null");
+        return MaybeAwait.get(this, defaultValue);
+    }
+
     /**
      * Casts the success value of the current Maybe into the target type or signals a
      * ClassCastException if not compatible.
@@ -739,7 +766,7 @@ public final <U> Maybe<U> cast(final Class<? extends U> clazz) {
     public final <R> Maybe<R> compose(Function<? super Maybe<T>, ? extends MaybeSource<R>> transformer) {
         return wrap(to(transformer));
     }
-
+    
     /**
      * Returns a Maybe that is based on applying a specified function to the item emitted by the source Maybe,
      * where that function returns a MaybeSource.
@@ -857,7 +884,7 @@ public final Maybe<T> doOnError(Consumer<? super Throwable> onError) {
                 Functions.EMPTY_ACTION     // dispose
         ));
     }
-    
+
     /**
      * Calls the given onEvent callback with the (success value, null) for an onSuccess, (null, throwabe) for
      * an onError or (null, null) for an onComplete signal from this Maybe before delivering said
@@ -964,6 +991,69 @@ public final <R> Maybe<R> flatMap(Function<? super T, ? extends MaybeSource<? ex
         return RxJavaPlugins.onAssembly(new MaybeFlatten<T, R>(this, mapper));
     }
 
+    /**
+     * Returns a Observable that is based on applying a specified function to the item emitted by the source Maybe,
+     * where that function returns a ObservableSource.
+     * <p>
+     * <img width="640" height="300" src="https://raw.github.com/wiki/ReactiveX/RxJava/images/rx-operators/Maybe.flatMap.png" alt="">
+     * <dl>
+     * <dt><b>Scheduler:</b></dt>
+     * <dd>{@code flatMap} does not operate by default on a particular {@link Scheduler}.</dd>
+     * </dl>
+     * 
+     * @param <R> the result value type
+     * @param mapper
+     *            a function that, when applied to the item emitted by the source Maybe, returns a ObservableSource
+     * @return the Observable returned from {@code func} when applied to the item emitted by the source Maybe
+     * @see <a href="http://reactivex.io/documentation/operators/flatmap.html">ReactiveX operators documentation: FlatMap</a>
+     */
+    public final <R> Observable<R> flatMapObservable(Function<? super T, ? extends ObservableSource<? extends R>> mapper) {
+        return toObservable().flatMap(mapper);
+    }
+
+    /**
+     * Returns a Flowable that emits items based on applying a specified function to the item emitted by the
+     * source Maybe, where that function returns a Publisher.
+     * <p>
+     * <img width="640" height="305" src="https://raw.github.com/wiki/ReactiveX/RxJava/images/rx-operators/Single.flatMapObservable.png" alt="">
+     * <dl>
+     * <dt><b>Scheduler:</b></dt>
+     * <dd>{@code flatMapObservable} does not operate by default on a particular {@link Scheduler}.</dd>
+     * </dl>
+     * 
+     * @param <R> the result value type
+     * @param mapper
+     *            a function that, when applied to the item emitted by the source Maybe, returns an
+     *            Flowable
+     * @return the Flowable returned from {@code func} when applied to the item emitted by the source Maybe
+     * @see <a href="http://reactivex.io/documentation/operators/flatmap.html">ReactiveX operators documentation: FlatMap</a>
+     */
+    public final <R> Flowable<R> flatMapPublisher(Function<? super T, ? extends Publisher<? extends R>> mapper) {
+        return toFlowable().flatMap(mapper);
+    }
+
+    /**
+     * Returns a {@link Completable} that completes based on applying a specified function to the item emitted by the
+     * source {@link Single}, where that function returns a {@link Completable}.
+     * <p>
+     * <img width="640" height="305" src="https://raw.github.com/wiki/ReactiveX/RxJava/images/rx-operators/Single.flatMapCompletable.png" alt="">
+     * <dl>
+     * <dt><b>Scheduler:</b></dt>
+     * <dd>{@code flatMapCompletable} does not operate by default on a particular {@link Scheduler}.</dd>
+     * </dl>
+     *
+     * @param mapper
+     *            a function that, when applied to the item emitted by the source Single, returns a
+     *            Completable
+     * @return the Completable returned from {@code func} when applied to the item emitted by the source Single
+     * @see <a href="http://reactivex.io/documentation/operators/flatmap.html">ReactiveX operators documentation: FlatMap</a>
+     * @since 2.0
+     */
+    public final Completable flatMapCompletable(final Function<? super T, ? extends Completable> mapper) {
+        ObjectHelper.requireNonNull(mapper, "mapper is null");
+        return RxJavaPlugins.onAssembly(new MaybeFlatMapCompletable<T>(this, mapper));
+    }
+
     /**
      * Maps the onSuccess, onError or onComplete signals of this Maybe into MaybeSource and emits that
      * MaybeSource's signals
@@ -1148,6 +1238,20 @@ public final Observable<T> toObservable() {
         return RxJavaPlugins.onAssembly(new MaybeToObservable<T>(this));
     }
 
+    /**
+     * Converts this Maybe into an Single instance composing cancellation
+     * through and turing an empty Maybe into a signal of NoSuchElementException.
+     * <dl>
+     *  <dt><b>Scheduler:</b></dt>
+     *  <dd>{@code create} does not operate by default on a particular {@link Scheduler}.</dd>
+     * </dl>
+     * @return the new Single instance
+     */
+    public final Single<T> toSingle(T defaultValue) {
+        ObjectHelper.requireNonNull(defaultValue, "defaultValue is null");
+        return RxJavaPlugins.onAssembly(new MaybeToSingle<T>(this, defaultValue));
+    }
+
     /**
      * Converts this Maybe into an Single instance composing cancellation
      * through and turing an empty Maybe into a signal of NoSuchElementException.
@@ -1158,7 +1262,7 @@ public final Observable<T> toObservable() {
      * @return the new Single instance
      */
     public final Single<T> toSingle() {
-        return RxJavaPlugins.onAssembly(new MaybeToSingle<T>(this));
+        return RxJavaPlugins.onAssembly(new MaybeToSingle<T>(this, null));
     }
 
     /**