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Single.java
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/**
* Copyright (c) 2016-present, RxJava Contributors.
*
* 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 io.reactivex;
import java.util.NoSuchElementException;
import java.util.concurrent.*;
import org.reactivestreams.Publisher;
import io.reactivex.annotations.*;
import io.reactivex.disposables.Disposable;
import io.reactivex.exceptions.Exceptions;
import io.reactivex.functions.*;
import io.reactivex.internal.functions.*;
import io.reactivex.internal.fuseable.*;
import io.reactivex.internal.observers.*;
import io.reactivex.internal.operators.completable.*;
import io.reactivex.internal.operators.flowable.*;
import io.reactivex.internal.operators.maybe.*;
import io.reactivex.internal.operators.mixed.*;
import io.reactivex.internal.operators.observable.*;
import io.reactivex.internal.operators.single.*;
import io.reactivex.internal.util.*;
import io.reactivex.observers.TestObserver;
import io.reactivex.plugins.RxJavaPlugins;
import io.reactivex.schedulers.Schedulers;
/**
* The {@code Single} class implements the Reactive Pattern for a single value response.
* <p>
* {@code Single} behaves similarly to {@link Observable} except that it can only emit either a single successful
* value or an error (there is no "onComplete" notification as there is for an {@link Observable}).
* <p>
* The {@code Single} class implements the {@link SingleSource} base interface and the default consumer
* type it interacts with is the {@link SingleObserver} via the {@link #subscribe(SingleObserver)} method.
* <p>
* The {@code Single} operates with the following sequential protocol:
* <pre>
* <code>onSubscribe (onSuccess | onError)?</code>
* </pre>
* <p>
* Note that {@code onSuccess} and {@code onError} are mutually exclusive events; unlike {@code Observable},
* {@code onSuccess} is never followed by {@code onError}.
* <p>
* Like {@code Observable}, a running {@code Single} can be stopped through the {@link Disposable} instance
* provided to consumers through {@link SingleObserver#onSubscribe}.
* <p>
* Like an {@code Observable}, a {@code Single} is lazy, can be either "hot" or "cold", synchronous or
* asynchronous. {@code Single} instances returned by the methods of this class are <em>cold</em>
* and there is a standard <em>hot</em> implementation in the form of a subject:
* {@link io.reactivex.subjects.SingleSubject SingleSubject}.
* <p>
* The documentation for this class makes use of marble diagrams. The following legend explains these diagrams:
* <p>
* <img width="640" height="301" src="https://raw.github.com/wiki/ReactiveX/RxJava/images/rx-operators/Single.legend.png" alt="">
* <p>
* See {@link Flowable} or {@link Observable} for the
* implementation of the Reactive Pattern for a stream or vector of values.
* <p>
* For more information see the <a href="http://reactivex.io/documentation/single.html">ReactiveX
* documentation</a>.
* <p>
* Example:
* <pre><code>
* Disposable d = Single.just("Hello World")
* .delay(10, TimeUnit.SECONDS, Schedulers.io())
* .subscribeWith(new DisposableSingleObserver<String>() {
* @Override
* public void onStart() {
* System.out.println("Started");
* }
*
* @Override
* public void onSuccess(String value) {
* System.out.println("Success: " + value);
* }
*
* @Override
* public void onError(Throwable error) {
* error.printStackTrace();
* }
* });
*
* Thread.sleep(5000);
*
* d.dispose();
* </code></pre>
* <p>
* Note that by design, subscriptions via {@link #subscribe(SingleObserver)} can't be disposed
* from the outside (hence the
* {@code void} return of the {@link #subscribe(SingleObserver)} method) and it is the
* responsibility of the implementor of the {@code SingleObserver} to allow this to happen.
* RxJava supports such usage with the standard
* {@link io.reactivex.observers.DisposableSingleObserver DisposableSingleObserver} instance.
* For convenience, the {@link #subscribeWith(SingleObserver)} method is provided as well to
* allow working with a {@code SingleObserver} (or subclass) instance to be applied with in
* a fluent manner (such as in the example above).
* @param <T>
* the type of the item emitted by the Single
* @since 2.0
* @see io.reactivex.observers.DisposableSingleObserver
*/
public abstract class Single<T> implements SingleSource<T> {
/**
* Runs multiple SingleSources and signals the events of the first one that signals (disposing
* the rest).
* <p>
* <img width="640" height="515" src="https://raw.github.com/wiki/ReactiveX/RxJava/images/rx-operators/Single.amb.png" alt="">
* <dl>
* <dt><b>Scheduler:</b></dt>
* <dd>{@code amb} does not operate by default on a particular {@link Scheduler}.</dd>
* </dl>
* @param <T> the value type
* @param sources the Iterable sequence of sources. A subscription to each source will
* occur in the same order as in this Iterable.
* @return the new Single instance
* @since 2.0
*/
@CheckReturnValue
@NonNull
@SchedulerSupport(SchedulerSupport.NONE)
public static <T> Single<T> amb(final Iterable<? extends SingleSource<? extends T>> sources) {
ObjectHelper.requireNonNull(sources, "sources is null");
return RxJavaPlugins.onAssembly(new SingleAmb<T>(null, sources));
}
/**
* Runs multiple SingleSources and signals the events of the first one that signals (disposing
* the rest).
* <p>
* <img width="640" height="515" src="https://raw.github.com/wiki/ReactiveX/RxJava/images/rx-operators/Single.ambArray.png" alt="">
* <dl>
* <dt><b>Scheduler:</b></dt>
* <dd>{@code ambArray} does not operate by default on a particular {@link Scheduler}.</dd>
* </dl>
* @param <T> the value type
* @param sources the array of sources. A subscription to each source will
* occur in the same order as in this array.
* @return the new Single instance
* @since 2.0
*/
@CheckReturnValue
@SchedulerSupport(SchedulerSupport.NONE)
@SuppressWarnings("unchecked")
public static <T> Single<T> ambArray(final SingleSource<? extends T>... sources) {
if (sources.length == 0) {
return error(SingleInternalHelper.<T>emptyThrower());
}
if (sources.length == 1) {
return wrap((SingleSource<T>)sources[0]);
}
return RxJavaPlugins.onAssembly(new SingleAmb<T>(sources, null));
}
/**
* Concatenate the single values, in a non-overlapping fashion, of the SingleSources provided by
* an Iterable sequence.
* <p>
* <img width="640" height="319" src="https://raw.github.com/wiki/ReactiveX/RxJava/images/rx-operators/Single.concat.i.png" alt="">
* <dl>
* <dt><b>Backpressure:</b></dt>
* <dd>The returned {@code Flowable} honors the backpressure of the downstream consumer.</dd>
* <dt><b>Scheduler:</b></dt>
* <dd>{@code concat} does not operate by default on a particular {@link Scheduler}.</dd>
* </dl>
* @param <T> the value type
* @param sources the Iterable sequence of SingleSource instances
* @return the new Flowable instance
* @since 2.0
*/
@CheckReturnValue
@NonNull
@SchedulerSupport(SchedulerSupport.NONE)
@BackpressureSupport(BackpressureKind.FULL)
public static <T> Flowable<T> concat(Iterable<? extends SingleSource<? extends T>> sources) {
return concat(Flowable.fromIterable(sources));
}
/**
* Concatenate the single values, in a non-overlapping fashion, of the SingleSources provided by
* an Observable sequence.
* <p>
* <img width="640" height="319" src="https://raw.github.com/wiki/ReactiveX/RxJava/images/rx-operators/Single.concat.o.png" alt="">
* <dl>
* <dt><b>Scheduler:</b></dt>
* <dd>{@code concat} does not operate by default on a particular {@link Scheduler}.</dd>
* </dl>
* @param <T> the value type
* @param sources the ObservableSource of SingleSource instances
* @return the new Observable instance
* @since 2.0
*/
@CheckReturnValue
@NonNull
@SchedulerSupport(SchedulerSupport.NONE)
@SuppressWarnings({ "unchecked", "rawtypes" })
public static <T> Observable<T> concat(ObservableSource<? extends SingleSource<? extends T>> sources) {
ObjectHelper.requireNonNull(sources, "sources is null");
return RxJavaPlugins.onAssembly(new ObservableConcatMap(sources, SingleInternalHelper.toObservable(), 2, ErrorMode.IMMEDIATE));
}
/**
* Concatenate the single values, in a non-overlapping fashion, of the SingleSources provided by
* a Publisher sequence.
* <p>
* <img width="640" height="308" src="https://raw.github.com/wiki/ReactiveX/RxJava/images/rx-operators/Single.concat.p.png" alt="">
* <dl>
* <dt><b>Backpressure:</b></dt>
* <dd>The returned {@code Flowable} honors the backpressure of the downstream consumer
* and the sources {@code Publisher} is expected to honor it as well.</dd>
* <dt><b>Scheduler:</b></dt>
* <dd>{@code concat} does not operate by default on a particular {@link Scheduler}.</dd>
* </dl>
* @param <T> the value type
* @param sources the Publisher of SingleSource instances
* @return the new Flowable instance
* @since 2.0
*/
@CheckReturnValue
@NonNull
@BackpressureSupport(BackpressureKind.FULL)
@SchedulerSupport(SchedulerSupport.NONE)
public static <T> Flowable<T> concat(Publisher<? extends SingleSource<? extends T>> sources) {
return concat(sources, 2);
}
/**
* Concatenate the single values, in a non-overlapping fashion, of the SingleSources provided by
* a Publisher sequence and prefetched by the specified amount.
* <p>
* <img width="640" height="310" src="https://raw.github.com/wiki/ReactiveX/RxJava/images/rx-operators/Single.concat.pn.png" alt="">
* <dl>
* <dt><b>Backpressure:</b></dt>
* <dd>The returned {@code Flowable} honors the backpressure of the downstream consumer
* and the sources {@code Publisher} is expected to honor it as well.</dd>
* <dt><b>Scheduler:</b></dt>
* <dd>{@code concat} does not operate by default on a particular {@link Scheduler}.</dd>
* </dl>
* @param <T> the value type
* @param sources the Publisher of SingleSource instances
* @param prefetch the number of SingleSources to prefetch from the Publisher
* @return the new Flowable instance
* @since 2.0
*/
@CheckReturnValue
@NonNull
@BackpressureSupport(BackpressureKind.FULL)
@SchedulerSupport(SchedulerSupport.NONE)
@SuppressWarnings({ "unchecked", "rawtypes" })
public static <T> Flowable<T> concat(Publisher<? extends SingleSource<? extends T>> sources, int prefetch) {
ObjectHelper.requireNonNull(sources, "sources is null");
ObjectHelper.verifyPositive(prefetch, "prefetch");
return RxJavaPlugins.onAssembly(new FlowableConcatMapPublisher(sources, SingleInternalHelper.toFlowable(), prefetch, ErrorMode.IMMEDIATE));
}
/**
* Returns a Flowable that emits the items emitted by two Singles, one after the other.
* <p>
* <img width="640" height="366" src="https://raw.github.com/wiki/ReactiveX/RxJava/images/rx-operators/Single.concat.png" alt="">
* <dl>
* <dt><b>Backpressure:</b></dt>
* <dd>The returned {@code Flowable} honors the backpressure of the downstream consumer.</dd>
* <dt><b>Scheduler:</b></dt>
* <dd>{@code concat} does not operate by default on a particular {@link Scheduler}.</dd>
* </dl>
*
* @param <T> the common value type
* @param source1
* a Single to be concatenated
* @param source2
* a Single to be concatenated
* @return a Flowable that emits items emitted by the two source Singles, one after the other.
* @see <a href="http://reactivex.io/documentation/operators/concat.html">ReactiveX operators documentation: Concat</a>
*/
@CheckReturnValue
@NonNull
@BackpressureSupport(BackpressureKind.FULL)
@SchedulerSupport(SchedulerSupport.NONE)
@SuppressWarnings("unchecked")
public static <T> Flowable<T> concat(
SingleSource<? extends T> source1, SingleSource<? extends T> source2
) {
ObjectHelper.requireNonNull(source1, "source1 is null");
ObjectHelper.requireNonNull(source2, "source2 is null");
return concat(Flowable.fromArray(source1, source2));
}
/**
* Returns a Flowable that emits the items emitted by three Singles, one after the other.
* <p>
* <img width="640" height="366" src="https://raw.github.com/wiki/ReactiveX/RxJava/images/rx-operators/Single.concat.o3.png" alt="">
* <dl>
* <dt><b>Backpressure:</b></dt>
* <dd>The returned {@code Flowable} honors the backpressure of the downstream consumer.</dd>
* <dt><b>Scheduler:</b></dt>
* <dd>{@code concat} does not operate by default on a particular {@link Scheduler}.</dd>
* </dl>
*
* @param <T> the common value type
* @param source1
* a Single to be concatenated
* @param source2
* a Single to be concatenated
* @param source3
* a Single to be concatenated
* @return a Flowable that emits items emitted by the three source Singles, one after the other.
* @see <a href="http://reactivex.io/documentation/operators/concat.html">ReactiveX operators documentation: Concat</a>
*/
@CheckReturnValue
@NonNull
@BackpressureSupport(BackpressureKind.FULL)
@SchedulerSupport(SchedulerSupport.NONE)
@SuppressWarnings("unchecked")
public static <T> Flowable<T> concat(
SingleSource<? extends T> source1, SingleSource<? extends T> source2,
SingleSource<? extends T> source3
) {
ObjectHelper.requireNonNull(source1, "source1 is null");
ObjectHelper.requireNonNull(source2, "source2 is null");
ObjectHelper.requireNonNull(source3, "source3 is null");
return concat(Flowable.fromArray(source1, source2, source3));
}
/**
* Returns a Flowable that emits the items emitted by four Singles, one after the other.
* <p>
* <img width="640" height="362" src="https://raw.github.com/wiki/ReactiveX/RxJava/images/rx-operators/Single.concat.o4.png" alt="">
* <dl>
* <dt><b>Backpressure:</b></dt>
* <dd>The returned {@code Flowable} honors the backpressure of the downstream consumer.</dd>
* <dt><b>Scheduler:</b></dt>
* <dd>{@code concat} does not operate by default on a particular {@link Scheduler}.</dd>
* </dl>
*
* @param <T> the common value type
* @param source1
* a Single to be concatenated
* @param source2
* a Single to be concatenated
* @param source3
* a Single to be concatenated
* @param source4
* a Single to be concatenated
* @return a Flowable that emits items emitted by the four source Singles, one after the other.
* @see <a href="http://reactivex.io/documentation/operators/concat.html">ReactiveX operators documentation: Concat</a>
*/
@CheckReturnValue
@NonNull
@BackpressureSupport(BackpressureKind.FULL)
@SchedulerSupport(SchedulerSupport.NONE)
@SuppressWarnings("unchecked")
public static <T> Flowable<T> concat(
SingleSource<? extends T> source1, SingleSource<? extends T> source2,
SingleSource<? extends T> source3, SingleSource<? extends T> source4
) {
ObjectHelper.requireNonNull(source1, "source1 is null");
ObjectHelper.requireNonNull(source2, "source2 is null");
ObjectHelper.requireNonNull(source3, "source3 is null");
ObjectHelper.requireNonNull(source4, "source4 is null");
return concat(Flowable.fromArray(source1, source2, source3, source4));
}
/**
* Concatenate the single values, in a non-overlapping fashion, of the SingleSources provided in
* an array.
* <p>
* <img width="640" height="319" src="https://raw.github.com/wiki/ReactiveX/RxJava/images/rx-operators/Single.concatArray.png" alt="">
* <dl>
* <dt><b>Backpressure:</b></dt>
* <dd>The returned {@code Flowable} honors the backpressure of the downstream consumer.</dd>
* <dt><b>Scheduler:</b></dt>
* <dd>{@code concatArray} does not operate by default on a particular {@link Scheduler}.</dd>
* </dl>
* @param <T> the value type
* @param sources the array of SingleSource instances
* @return the new Flowable instance
* @since 2.0
*/
@CheckReturnValue
@NonNull
@BackpressureSupport(BackpressureKind.FULL)
@SchedulerSupport(SchedulerSupport.NONE)
@SuppressWarnings({ "unchecked", "rawtypes" })
public static <T> Flowable<T> concatArray(SingleSource<? extends T>... sources) {
return RxJavaPlugins.onAssembly(new FlowableConcatMap(Flowable.fromArray(sources), SingleInternalHelper.toFlowable(), 2, ErrorMode.BOUNDARY));
}
/**
* Concatenates a sequence of SingleSource eagerly into a single stream of values.
* <p>
* Eager concatenation means that once a subscriber subscribes, this operator subscribes to all of the
* source SingleSources. The operator buffers the value emitted by these SingleSources and then drains them
* in order, each one after the previous one completes.
* <dl>
* <dt><b>Backpressure:</b></dt>
* <dd>The operator honors backpressure from downstream.</dd>
* <dt><b>Scheduler:</b></dt>
* <dd>This method does not operate by default on a particular {@link Scheduler}.</dd>
* </dl>
* @param <T> the value type
* @param sources a sequence of Single that need to be eagerly concatenated
* @return the new Flowable instance with the specified concatenation behavior
*/
@BackpressureSupport(BackpressureKind.FULL)
@CheckReturnValue
@NonNull
@SchedulerSupport(SchedulerSupport.NONE)
public static <T> Flowable<T> concatArrayEager(SingleSource<? extends T>... sources) {
return Flowable.fromArray(sources).concatMapEager(SingleInternalHelper.<T>toFlowable());
}
/**
* Concatenates a Publisher sequence of SingleSources eagerly into a single stream of values.
* <p>
* <img width="640" height="307" src="https://raw.github.com/wiki/ReactiveX/RxJava/images/rx-operators/Single.concatEager.p.png" alt="">
* <p>
* Eager concatenation means that once a subscriber subscribes, this operator subscribes to all of the
* emitted source Publishers as they are observed. The operator buffers the values emitted by these
* Publishers and then drains them in order, each one after the previous one completes.
* <dl>
* <dt><b>Backpressure:</b></dt>
* <dd>Backpressure is honored towards the downstream and the outer Publisher is
* expected to support backpressure. Violating this assumption, the operator will
* signal {@link io.reactivex.exceptions.MissingBackpressureException}.</dd>
* <dt><b>Scheduler:</b></dt>
* <dd>This method does not operate by default on a particular {@link Scheduler}.</dd>
* </dl>
* @param <T> the value type
* @param sources a sequence of Publishers that need to be eagerly concatenated
* @return the new Publisher instance with the specified concatenation behavior
*/
@BackpressureSupport(BackpressureKind.FULL)
@CheckReturnValue
@NonNull
@SchedulerSupport(SchedulerSupport.NONE)
public static <T> Flowable<T> concatEager(Publisher<? extends SingleSource<? extends T>> sources) {
return Flowable.fromPublisher(sources).concatMapEager(SingleInternalHelper.<T>toFlowable());
}
/**
* Concatenates a sequence of SingleSources eagerly into a single stream of values.
* <p>
* <img width="640" height="319" src="https://raw.github.com/wiki/ReactiveX/RxJava/images/rx-operators/Single.concatEager.i.png" alt="">
* <p>
* Eager concatenation means that once a subscriber subscribes, this operator subscribes to all of the
* source SingleSources. The operator buffers the values emitted by these SingleSources and then drains them
* in order, each one after the previous one completes.
* <dl>
* <dt><b>Backpressure:</b></dt>
* <dd>Backpressure is honored towards the downstream.</dd>
* <dt><b>Scheduler:</b></dt>
* <dd>This method does not operate by default on a particular {@link Scheduler}.</dd>
* </dl>
* @param <T> the value type
* @param sources a sequence of SingleSource that need to be eagerly concatenated
* @return the new Flowable instance with the specified concatenation behavior
*/
@BackpressureSupport(BackpressureKind.FULL)
@CheckReturnValue
@NonNull
@SchedulerSupport(SchedulerSupport.NONE)
public static <T> Flowable<T> concatEager(Iterable<? extends SingleSource<? extends T>> sources) {
return Flowable.fromIterable(sources).concatMapEager(SingleInternalHelper.<T>toFlowable());
}
/**
* Provides an API (via a cold Single) that bridges the reactive world with the callback-style world.
* <p>
* <img width="640" height="454" src="https://raw.github.com/wiki/ReactiveX/RxJava/images/rx-operators/Single.create.png" alt="">
* <p>
* Example:
* <pre><code>
* Single.<Event>create(emitter -> {
* Callback listener = new Callback() {
* @Override
* public void onEvent(Event e) {
* emitter.onSuccess(e);
* }
*
* @Override
* public void onFailure(Exception e) {
* emitter.onError(e);
* }
* };
*
* AutoCloseable c = api.someMethod(listener);
*
* emitter.setCancellable(c::close);
*
* });
* </code></pre>
* <p>
* Whenever a {@link SingleObserver} subscribes to the returned {@code Single}, the provided
* {@link SingleOnSubscribe} callback is invoked with a fresh instance of a {@link SingleEmitter}
* that will interact only with that specific {@code SingleObserver}. If this {@code SingleObserver}
* disposes the flow (making {@link SingleEmitter#isDisposed} return true),
* other observers subscribed to the same returned {@code Single} are not affected.
* <dl>
* <dt><b>Scheduler:</b></dt>
* <dd>{@code create} does not operate by default on a particular {@link Scheduler}.</dd>
* </dl>
* @param <T> the value type
* @param source the emitter that is called when a SingleObserver subscribes to the returned {@code Single}
* @return the new Single instance
* @see SingleOnSubscribe
* @see Cancellable
*/
@CheckReturnValue
@NonNull
@SchedulerSupport(SchedulerSupport.NONE)
public static <T> Single<T> create(SingleOnSubscribe<T> source) {
ObjectHelper.requireNonNull(source, "source is null");
return RxJavaPlugins.onAssembly(new SingleCreate<T>(source));
}
/**
* Calls a {@link Supplier} for each individual {@link SingleObserver} to return the actual {@link SingleSource} to
* be subscribed to.
* <p>
* <img width="640" height="515" src="https://raw.github.com/wiki/ReactiveX/RxJava/images/rx-operators/Single.defer.png" alt="">
* <dl>
* <dt><b>Scheduler:</b></dt>
* <dd>{@code defer} does not operate by default on a particular {@link Scheduler}.</dd>
* </dl>
* @param <T> the value type
* @param singleSupplier the {@code Supplier} that is called for each individual {@code SingleObserver} and
* returns a SingleSource instance to subscribe to
* @return the new Single instance
*/
@CheckReturnValue
@NonNull
@SchedulerSupport(SchedulerSupport.NONE)
public static <T> Single<T> defer(final Supplier<? extends SingleSource<? extends T>> singleSupplier) {
ObjectHelper.requireNonNull(singleSupplier, "singleSupplier is null");
return RxJavaPlugins.onAssembly(new SingleDefer<T>(singleSupplier));
}
/**
* Signals a Throwable returned by the callback function for each individual SingleObserver.
* <p>
* <img width="640" height="283" src="https://raw.github.com/wiki/ReactiveX/RxJava/images/rx-operators/Single.error.c.png" alt="">
* <dl>
* <dt><b>Scheduler:</b></dt>
* <dd>{@code error} does not operate by default on a particular {@link Scheduler}.</dd>
* </dl>
* @param <T> the value type
* @param errorSupplier the Supplier that is called for each individual SingleObserver and
* returns a Throwable instance to be emitted.
* @return the new Single instance
*/
@CheckReturnValue
@NonNull
@SchedulerSupport(SchedulerSupport.NONE)
public static <T> Single<T> error(final Supplier<? extends Throwable> errorSupplier) {
ObjectHelper.requireNonNull(errorSupplier, "errorSupplier is null");
return RxJavaPlugins.onAssembly(new SingleError<T>(errorSupplier));
}
/**
* Returns a Single that invokes a subscriber's {@link SingleObserver#onError onError} method when the
* subscriber subscribes to it.
* <p>
* <img width="640" height="283" src="https://raw.github.com/wiki/ReactiveX/RxJava/images/rx-operators/Single.error.png" alt="">
* <dl>
* <dt><b>Scheduler:</b></dt>
* <dd>{@code error} does not operate by default on a particular {@link Scheduler}.</dd>
* </dl>
*
* @param exception
* the particular Throwable to pass to {@link SingleObserver#onError onError}
* @param <T>
* the type of the item (ostensibly) emitted by the Single
* @return a Single that invokes the subscriber's {@link SingleObserver#onError onError} method when
* the subscriber subscribes to it
* @see <a href="http://reactivex.io/documentation/operators/empty-never-throw.html">ReactiveX operators documentation: Throw</a>
*/
@CheckReturnValue
@NonNull
@SchedulerSupport(SchedulerSupport.NONE)
public static <T> Single<T> error(final Throwable exception) {
ObjectHelper.requireNonNull(exception, "exception is null");
return error(Functions.justSupplier(exception));
}
/**
* Returns a {@link Single} that invokes passed function and emits its result for each new SingleObserver that subscribes.
* <p>
* Allows you to defer execution of passed function until SingleObserver subscribes to the {@link Single}.
* It makes passed function "lazy".
* Result of the function invocation will be emitted by the {@link Single}.
* <p>
* <img width="640" height="467" src="https://raw.github.com/wiki/ReactiveX/RxJava/images/rx-operators/Single.fromCallable.png" alt="">
* <dl>
* <dt><b>Scheduler:</b></dt>
* <dd>{@code fromCallable} does not operate by default on a particular {@link Scheduler}.</dd>
* <dt><b>Error handling:</b></dt>
* <dd> If the {@link Callable} throws an exception, the respective {@link Throwable} is
* delivered to the downstream via {@link SingleObserver#onError(Throwable)},
* except when the downstream has disposed this {@code Single} source.
* In this latter case, the {@code Throwable} is delivered to the global error handler via
* {@link RxJavaPlugins#onError(Throwable)} as an {@link io.reactivex.exceptions.UndeliverableException UndeliverableException}.
* </dd>
* </dl>
*
* @param callable
* function which execution should be deferred, it will be invoked when SingleObserver will subscribe to the {@link Single}.
* @param <T>
* the type of the item emitted by the {@link Single}.
* @return a {@link Single} whose {@link SingleObserver}s' subscriptions trigger an invocation of the given function.
* @see #defer(Supplier)
* @see #fromSupplier(Supplier)
*/
@CheckReturnValue
@NonNull
@SchedulerSupport(SchedulerSupport.NONE)
public static <T> Single<T> fromCallable(final Callable<? extends T> callable) {
ObjectHelper.requireNonNull(callable, "callable is null");
return RxJavaPlugins.onAssembly(new SingleFromCallable<T>(callable));
}
/**
* Converts a {@link Future} into a {@code Single}.
* <p>
* <img width="640" height="315" src="https://raw.github.com/wiki/ReactiveX/RxJava/images/rx-operators/Single.from.Future.png" alt="">
* <p>
* You can convert any object that supports the {@link Future} interface into a Single that emits the return
* value of the {@link Future#get} method of that object, by passing the object into the {@code from}
* method.
* <p>
* <em>Important note:</em> This Single is blocking; you cannot dispose it.
* <dl>
* <dt><b>Scheduler:</b></dt>
* <dd>{@code fromFuture} does not operate by default on a particular {@link Scheduler}.</dd>
* </dl>
*
* @param future
* the source {@link Future}
* @param <T>
* the type of object that the {@link Future} returns, and also the type of item to be emitted by
* the resulting {@code Single}
* @return a {@code Single} that emits the item from the source {@link Future}
* @see <a href="http://reactivex.io/documentation/operators/from.html">ReactiveX operators documentation: From</a>
*/
@CheckReturnValue
@SchedulerSupport(SchedulerSupport.NONE)
public static <T> Single<T> fromFuture(Future<? extends T> future) {
return toSingle(Flowable.<T>fromFuture(future));
}
/**
* Converts a {@link Future} into a {@code Single}, with a timeout on the Future.
* <p>
* <img width="640" height="315" src="https://raw.github.com/wiki/ReactiveX/RxJava/images/rx-operators/Single.from.Future.png" alt="">
* <p>
* You can convert any object that supports the {@link Future} interface into a {@code Single} that emits
* the return value of the {@link Future#get} method of that object, by passing the object into the
* {@code from} method.
* <p>
* <em>Important note:</em> This {@code Single} is blocking; you cannot dispose it.
* <dl>
* <dt><b>Scheduler:</b></dt>
* <dd>{@code fromFuture} does not operate by default on a particular {@link Scheduler}.</dd>
* </dl>
*
* @param future
* the source {@link Future}
* @param timeout
* the maximum time to wait before calling {@code get}
* @param unit
* the {@link TimeUnit} of the {@code timeout} argument
* @param <T>
* the type of object that the {@link Future} returns, and also the type of item to be emitted by
* the resulting {@code Single}
* @return a {@code Single} that emits the item from the source {@link Future}
* @see <a href="http://reactivex.io/documentation/operators/from.html">ReactiveX operators documentation: From</a>
*/
@CheckReturnValue
@SchedulerSupport(SchedulerSupport.NONE)
public static <T> Single<T> fromFuture(Future<? extends T> future, long timeout, TimeUnit unit) {
return toSingle(Flowable.<T>fromFuture(future, timeout, unit));
}
/**
* Converts a {@link Future} into a {@code Single}, with a timeout on the Future.
* <p>
* <img width="640" height="315" src="https://raw.github.com/wiki/ReactiveX/RxJava/images/rx-operators/Single.from.Future.png" alt="">
* <p>
* You can convert any object that supports the {@link Future} interface into a {@code Single} that emits
* the return value of the {@link Future#get} method of that object, by passing the object into the
* {@code from} method.
* <p>
* <em>Important note:</em> This {@code Single} is blocking; you cannot dispose it.
* <dl>
* <dt><b>Scheduler:</b></dt>
* <dd>You specify the {@link Scheduler} where the blocking wait will happen.</dd>
* </dl>
*
* @param future
* the source {@link Future}
* @param timeout
* the maximum time to wait before calling {@code get}
* @param unit
* the {@link TimeUnit} of the {@code timeout} argument
* @param scheduler
* the Scheduler to use for the blocking wait
* @param <T>
* the type of object that the {@link Future} returns, and also the type of item to be emitted by
* the resulting {@code Single}
* @return a {@code Single} that emits the item from the source {@link Future}
* @see <a href="http://reactivex.io/documentation/operators/from.html">ReactiveX operators documentation: From</a>
*/
@CheckReturnValue
@SchedulerSupport(SchedulerSupport.CUSTOM)
public static <T> Single<T> fromFuture(Future<? extends T> future, long timeout, TimeUnit unit, Scheduler scheduler) {
return toSingle(Flowable.<T>fromFuture(future, timeout, unit, scheduler));
}
/**
* Converts a {@link Future}, operating on a specified {@link Scheduler}, into a {@code Single}.
* <p>
* <img width="640" height="315" src="https://raw.github.com/wiki/ReactiveX/RxJava/images/rx-operators/Single.from.Future.s.png" alt="">
* <p>
* You can convert any object that supports the {@link Future} interface into a {@code Single} that emits
* the return value of the {@link Future#get} method of that object, by passing the object into the
* {@code from} method.
* <dl>
* <dt><b>Scheduler:</b></dt>
* <dd>You specify which {@link Scheduler} this operator will use.</dd>
* </dl>
*
* @param future
* the source {@link Future}
* @param scheduler
* the {@link Scheduler} to wait for the Future on. Use a Scheduler such as
* {@link Schedulers#io()} that can block and wait on the Future
* @param <T>
* the type of object that the {@link Future} returns, and also the type of item to be emitted by
* the resulting {@code Single}
* @return a {@code Single} that emits the item from the source {@link Future}
* @see <a href="http://reactivex.io/documentation/operators/from.html">ReactiveX operators documentation: From</a>
*/
@CheckReturnValue
@SchedulerSupport(SchedulerSupport.CUSTOM)
public static <T> Single<T> fromFuture(Future<? extends T> future, Scheduler scheduler) {
return toSingle(Flowable.<T>fromFuture(future, scheduler));
}
/**
* Wraps a specific Publisher into a Single and signals its single element or error.
* <p>If the source Publisher is empty, a NoSuchElementException is signalled. If
* the source has more than one element, an IndexOutOfBoundsException is signalled.
* <p>
* The {@link Publisher} must follow the
* <a href="https://github.com/reactive-streams/reactive-streams-jvm#reactive-streams">Reactive-Streams specification</a>.
* Violating the specification may result in undefined behavior.
* <p>
* If possible, use {@link #create(SingleOnSubscribe)} to create a
* source-like {@code Single} instead.
* <p>
* Note that even though {@link Publisher} appears to be a functional interface, it
* is not recommended to implement it through a lambda as the specification requires
* state management that is not achievable with a stateless lambda.
* <p>
* <img width="640" height="322" src="https://raw.github.com/wiki/ReactiveX/RxJava/images/rx-operators/Single.fromPublisher.png" alt="">
* <dl>
* <dt><b>Backpressure:</b></dt>
* <dd>The {@code publisher} is consumed in an unbounded fashion but will be cancelled
* if it produced more than one item.</dd>
* <dt><b>Scheduler:</b></dt>
* <dd>{@code fromPublisher} does not operate by default on a particular {@link Scheduler}.</dd>
* </dl>
* @param <T> the value type
* @param publisher the source Publisher instance, not null
* @return the new Single instance
* @see #create(SingleOnSubscribe)
*/
@BackpressureSupport(BackpressureKind.UNBOUNDED_IN)
@CheckReturnValue
@NonNull
@SchedulerSupport(SchedulerSupport.NONE)
public static <T> Single<T> fromPublisher(final Publisher<? extends T> publisher) {
ObjectHelper.requireNonNull(publisher, "publisher is null");
return RxJavaPlugins.onAssembly(new SingleFromPublisher<T>(publisher));
}
/**
* Wraps a specific ObservableSource into a Single and signals its single element or error.
* <p>If the ObservableSource is empty, a NoSuchElementException is signalled.
* If the source has more than one element, an IndexOutOfBoundsException is signalled.
* <p>
* <img width="640" height="343" src="https://raw.github.com/wiki/ReactiveX/RxJava/images/rx-operators/Single.fromObservable.png" alt="">
* <dl>
* <dt><b>Scheduler:</b></dt>
* <dd>{@code fromObservable} does not operate by default on a particular {@link Scheduler}.</dd>
* </dl>
*
* @param observableSource the source Observable, not null
* @param <T>
* the type of the item emitted by the {@link Single}.
* @return the new Single instance
*/
@CheckReturnValue
@NonNull
@SchedulerSupport(SchedulerSupport.NONE)
public static <T> Single<T> fromObservable(ObservableSource<? extends T> observableSource) {
ObjectHelper.requireNonNull(observableSource, "observableSource is null");
return RxJavaPlugins.onAssembly(new ObservableSingleSingle<T>(observableSource, null));
}
/**
* Returns a {@link Single} that invokes passed supplierfunction and emits its result
* for each new SingleObserver that subscribes.
* <p>
* Allows you to defer execution of passed function until SingleObserver subscribes to the {@link Single}.
* It makes passed function "lazy".
* Result of the function invocation will be emitted by the {@link Single}.
* <p>
* <img width="640" height="467" src="https://raw.github.com/wiki/ReactiveX/RxJava/images/rx-operators/Single.fromSupplier.png" alt="">
* <dl>
* <dt><b>Scheduler:</b></dt>
* <dd>{@code fromSupplier} does not operate by default on a particular {@link Scheduler}.</dd>
* <dt><b>Error handling:</b></dt>
* <dd> If the {@link Supplier} throws an exception, the respective {@link Throwable} is
* delivered to the downstream via {@link SingleObserver#onError(Throwable)},
* except when the downstream has disposed this {@code Single} source.
* In this latter case, the {@code Throwable} is delivered to the global error handler via
* {@link RxJavaPlugins#onError(Throwable)} as an {@link io.reactivex.exceptions.UndeliverableException UndeliverableException}.
* </dd>
* </dl>
*
* @param supplier
* function which execution should be deferred, it will be invoked when SingleObserver will subscribe to the {@link Single}.
* @param <T>
* the type of the item emitted by the {@link Single}.
* @return a {@link Single} whose {@link SingleObserver}s' subscriptions trigger an invocation of the given function.
* @see #defer(Supplier)
* @see #fromCallable(Callable)
* @since 3.0.0
*/
@CheckReturnValue
@NonNull
@SchedulerSupport(SchedulerSupport.NONE)
public static <T> Single<T> fromSupplier(final Supplier<? extends T> supplier) {
ObjectHelper.requireNonNull(supplier, "supplier is null");
return RxJavaPlugins.onAssembly(new SingleFromSupplier<T>(supplier));
}
/**
* Returns a {@code Single} that emits a specified item.
* <p>
* <img width="640" height="310" src="https://raw.github.com/wiki/ReactiveX/RxJava/images/rx-operators/Single.just.png" alt="">
* <p>
* To convert any object into a {@code Single} that emits that object, pass that object into the
* {@code just} method.
* <dl>
* <dt><b>Scheduler:</b></dt>
* <dd>{@code just} does not operate by default on a particular {@link Scheduler}.</dd>
* </dl>
*
* @param item
* the item to emit
* @param <T>
* the type of that item
* @return a {@code Single} that emits {@code item}
* @see <a href="http://reactivex.io/documentation/operators/just.html">ReactiveX operators documentation: Just</a>
*/
@CheckReturnValue
@SchedulerSupport(SchedulerSupport.NONE)
@NonNull
public static <T> Single<T> just(final T item) {
ObjectHelper.requireNonNull(item, "item is null");
return RxJavaPlugins.onAssembly(new SingleJust<T>(item));
}
/**
* Merges an Iterable sequence of SingleSource instances into a single Flowable sequence,
* running all SingleSources at once.
* <p>
* <img width="640" height="319" src="https://raw.github.com/wiki/ReactiveX/RxJava/images/rx-operators/Single.merge.i.png" alt="">
* <dl>
* <dt><b>Backpressure:</b></dt>
* <dd>The returned {@code Flowable} honors the backpressure of the downstream consumer.</dd>
* <dt><b>Scheduler:</b></dt>
* <dd>{@code merge} does not operate by default on a particular {@link Scheduler}.</dd>
* <dt><b>Error handling:</b></dt>
* <dd>If any of the source {@code SingleSource}s signal a {@code Throwable} via {@code onError}, the resulting
* {@code Flowable} terminates with that {@code Throwable} and all other source {@code SingleSource}s are disposed.
* If more than one {@code SingleSource} signals an error, the resulting {@code Flowable} may terminate with the
* first one's error or, depending on the concurrency of the sources, may terminate with a
* {@code CompositeException} containing two or more of the various error signals.
* {@code Throwable}s that didn't make into the composite will be sent (individually) to the global error handler via
* {@link RxJavaPlugins#onError(Throwable)} method as {@code UndeliverableException} errors. Similarly, {@code Throwable}s
* signaled by source(s) after the returned {@code Flowable} has been cancelled or terminated with a
* (composite) error will be sent to the same global error handler.
* Use {@link #mergeDelayError(Iterable)} to merge sources and terminate only when all source {@code SingleSource}s
* have completed or failed with an error.
* </dd>
* </dl>
* @param <T> the common and resulting value type
* @param sources the Iterable sequence of SingleSource sources
* @return the new Flowable instance
* @since 2.0
* @see #mergeDelayError(Iterable)
*/
@CheckReturnValue
@NonNull
@BackpressureSupport(BackpressureKind.FULL)
@SchedulerSupport(SchedulerSupport.NONE)
public static <T> Flowable<T> merge(Iterable<? extends SingleSource<? extends T>> sources) {
return merge(Flowable.fromIterable(sources));
}
/**
* Merges a Flowable sequence of SingleSource instances into a single Flowable sequence,
* running all SingleSources at once.
* <p>
* <img width="640" height="307" src="https://raw.github.com/wiki/ReactiveX/RxJava/images/rx-operators/Single.merge.p.png" alt="">
* <dl>
* <dt><b>Backpressure:</b></dt>
* <dd>The returned {@code Flowable} honors the backpressure of the downstream consumer.</dd>
* <dt><b>Scheduler:</b></dt>
* <dd>{@code merge} does not operate by default on a particular {@link Scheduler}.</dd>
* <dt><b>Error handling:</b></dt>
* <dd>If any of the source {@code SingleSource}s signal a {@code Throwable} via {@code onError}, the resulting
* {@code Flowable} terminates with that {@code Throwable} and all other source {@code SingleSource}s are disposed.
* If more than one {@code SingleSource} signals an error, the resulting {@code Flowable} may terminate with the
* first one's error or, depending on the concurrency of the sources, may terminate with a
* {@code CompositeException} containing two or more of the various error signals.
* {@code Throwable}s that didn't make into the composite will be sent (individually) to the global error handler via
* {@link RxJavaPlugins#onError(Throwable)} method as {@code UndeliverableException} errors. Similarly, {@code Throwable}s
* signaled by source(s) after the returned {@code Flowable} has been cancelled or terminated with a
* (composite) error will be sent to the same global error handler.
* Use {@link #mergeDelayError(Publisher)} to merge sources and terminate only when all source {@code SingleSource}s
* have completed or failed with an error.
* </dd>
* </dl>
* @param <T> the common and resulting value type
* @param sources the Flowable sequence of SingleSource sources
* @return the new Flowable instance
* @see #mergeDelayError(Publisher)
* @since 2.0
*/
@CheckReturnValue
@NonNull
@BackpressureSupport(BackpressureKind.FULL)
@SchedulerSupport(SchedulerSupport.NONE)
@SuppressWarnings({ "unchecked", "rawtypes" })
public static <T> Flowable<T> merge(Publisher<? extends SingleSource<? extends T>> sources) {
ObjectHelper.requireNonNull(sources, "sources is null");
return RxJavaPlugins.onAssembly(new FlowableFlatMapPublisher(sources, SingleInternalHelper.toFlowable(), false, Integer.MAX_VALUE, Flowable.bufferSize()));
}
/**
* Flattens a {@code Single} that emits a {@code Single} into a single {@code Single} that emits the item
* emitted by the nested {@code Single}, without any transformation.
* <p>
* <img width="640" height="412" src="https://raw.github.com/wiki/ReactiveX/RxJava/images/rx-operators/Single.merge.oo.png" alt="">
* <dl>
* <dt><b>Scheduler:</b></dt>
* <dd>{@code merge} does not operate by default on a particular {@link Scheduler}.</dd>
* <dd>The resulting {@code Single} emits the outer source's or the inner {@code SingleSource}'s {@code Throwable} as is.
* Unlike the other {@code merge()} operators, this operator won't and can't produce a {@code CompositeException} because there is
* only one possibility for the outer or the inner {@code SingleSource} to emit an {@code onError} signal.
* Therefore, there is no need for a {@code mergeDelayError(SingleSource<SingleSource<T>>)} operator.
* </dd>
* </dl>
*
* @param <T> the value type of the sources and the output
* @param source
* a {@code Single} that emits a {@code Single}
* @return a {@code Single} that emits the item that is the result of flattening the {@code Single} emitted
* by {@code source}
* @see <a href="http://reactivex.io/documentation/operators/merge.html">ReactiveX operators documentation: Merge</a>
*/
@CheckReturnValue
@NonNull
@SchedulerSupport(SchedulerSupport.NONE)
@SuppressWarnings({ "unchecked", "rawtypes" })
public static <T> Single<T> merge(SingleSource<? extends SingleSource<? extends T>> source) {
ObjectHelper.requireNonNull(source, "source is null");
return RxJavaPlugins.onAssembly(new SingleFlatMap<SingleSource<? extends T>, T>(source, (Function)Functions.identity()));
}
/**
* Flattens two Singles into a single Flowable, without any transformation.
* <p>
* <img width="640" height="414" src="https://raw.github.com/wiki/ReactiveX/RxJava/images/rx-operators/Single.merge.png" alt="">
* <p>