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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.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 Single class implements the Reactive Pattern for a single value response.
* See {@link Flowable} or {@link Observable} for the
* implementation of the Reactive Pattern for a stream or vector of values.
* <p>
* {@code Single} behaves the same as {@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 {@link Observable})
* <p>
* Like an {@link Observable}, a {@code Single} is lazy, can be either "hot" or "cold", synchronous or
* asynchronous.
* <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>
* For more information see the <a href="http://reactivex.io/documentation/observable.html">ReactiveX
* documentation</a>.
*
* @param <T>
* the type of the item emitted by the Single
* @since 2.0
*/
public abstract class Single<T> implements SingleSource<T> {
/**
* Runs multiple Single sources and signals the events of the first one that signals (cancelling
* the rest).
* <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
@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 Single sources and signals the events of the first one that signals (cancelling
* the rest).
* <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 Single sources provided by
* an Iterable sequence.
* <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
@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 Single sources provided by
* an Observable sequence.
* <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
@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 Single sources provided by
* a Publisher sequence.
* <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
@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 Single sources provided by
* a Publisher sequence and prefetched by the specified amount.
* <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
@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="380" 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
@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="380" 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
* @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
@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="380" 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
* @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
@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 Single sources provided in
* an array.
* <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
@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));
}
/**
* Provides an API (via a cold Completable) that bridges the reactive world with the callback-style world.
* <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>
* <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
@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 Callable for each individual SingleObserver to return the actual Single source to
* be subscribed to.
* <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 Callable that is called for each individual SingleObserver and
* returns a SingleSource instance to subscribe to
* @return the new Single instance
*/
@CheckReturnValue
@SchedulerSupport(SchedulerSupport.NONE)
public static <T> Single<T> defer(final Callable<? 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.
* <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 callable that is called for each individual SingleObserver and
* returns a Throwable instance to be emitted.
* @return the new Single instance
*/
@CheckReturnValue
@SchedulerSupport(SchedulerSupport.NONE)
public static <T> Single<T> error(final Callable<? 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="190" 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
@SchedulerSupport(SchedulerSupport.NONE)
public static <T> Single<T> error(final Throwable exception) {
ObjectHelper.requireNonNull(exception, "error is null");
return error(Functions.justCallable(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}.
* <dl>
* <dt><b>Scheduler:</b></dt>
* <dd>{@code fromCallable} does not operate by default on a particular {@link Scheduler}.</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.
*/
@CheckReturnValue
@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.
* <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
@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.
* <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
@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 {@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)
public static <T> Single<T> just(final T item) {
ObjectHelper.requireNonNull(item, "value 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.
* <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>
* </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
*/
@CheckReturnValue
@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.
* <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>
* </dl>
* @param <T> the common and resulting value type
* @param sources the Flowable sequence of SingleSource sources
* @return the new Flowable instance
* @since 2.0
*/
@CheckReturnValue
@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="370" 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>
* </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
@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="380" src="https://raw.github.com/wiki/ReactiveX/RxJava/images/rx-operators/Single.merge.png" alt="">
* <p>
* You can combine items emitted by multiple Singles so that they appear as a single Flowable, by
* using the {@code merge} method.
* <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>
* </dl>
*
* @param <T> the common value type
* @param source1
* a Single to be merged
* @param source2
* a Single to be merged
* @return a Flowable that emits all of the items emitted by the source Singles
* @see <a href="http://reactivex.io/documentation/operators/merge.html">ReactiveX operators documentation: Merge</a>
*/
@CheckReturnValue
@BackpressureSupport(BackpressureKind.FULL)
@SchedulerSupport(SchedulerSupport.NONE)
@SuppressWarnings("unchecked")
public static <T> Flowable<T> merge(
SingleSource<? extends T> source1, SingleSource<? extends T> source2
) {
ObjectHelper.requireNonNull(source1, "source1 is null");
ObjectHelper.requireNonNull(source2, "source2 is null");
return merge(Flowable.fromArray(source1, source2));
}
/**
* Flattens three Singles into a single Flowable, without any transformation.
* <p>
* <img width="640" height="380" src="https://raw.github.com/wiki/ReactiveX/RxJava/images/rx-operators/Single.merge.png" alt="">
* <p>
* You can combine items emitted by multiple Singles so that they appear as a single Flowable, by using
* the {@code merge} method.
* <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>
* </dl>
*
* @param <T> the common value type
* @param source1
* a Single to be merged
* @param source2
* a Single to be merged
* @param source3
* a Single to be merged
* @return a Flowable that emits all of the items emitted by the source Singles
* @see <a href="http://reactivex.io/documentation/operators/merge.html">ReactiveX operators documentation: Merge</a>
*/
@CheckReturnValue
@BackpressureSupport(BackpressureKind.FULL)
@SchedulerSupport(SchedulerSupport.NONE)
@SuppressWarnings("unchecked")
public static <T> Flowable<T> merge(
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 merge(Flowable.fromArray(source1, source2, source3));
}
/**
* Flattens four Singles into a single Flowable, without any transformation.
* <p>
* <img width="640" height="380" src="https://raw.github.com/wiki/ReactiveX/RxJava/images/rx-operators/Single.merge.png" alt="">
* <p>
* You can combine items emitted by multiple Singles so that they appear as a single Flowable, by using
* the {@code merge} method.
* <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>
* </dl>
*
* @param <T> the common value type
* @param source1
* a Single to be merged
* @param source2
* a Single to be merged
* @param source3
* a Single to be merged
* @param source4
* a Single to be merged
* @return a Flowable that emits all of the items emitted by the source Singles
* @see <a href="http://reactivex.io/documentation/operators/merge.html">ReactiveX operators documentation: Merge</a>
*/
@CheckReturnValue
@BackpressureSupport(BackpressureKind.FULL)
@SchedulerSupport(SchedulerSupport.NONE)
@SuppressWarnings("unchecked")
public static <T> Flowable<T> merge(
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 merge(Flowable.fromArray(source1, source2, source3, source4));
}
/**
* Returns a singleton instance of a never-signalling Single (only calls onSubscribe).
* <dl>
* <dt><b>Scheduler:</b></dt>
* <dd>{@code never} does not operate by default on a particular {@link Scheduler}.</dd>
* </dl>
* @param <T> the target value type
* @return the singleton never instance
* @since 2.0
*/
@CheckReturnValue
@SchedulerSupport(SchedulerSupport.NONE)
@SuppressWarnings("unchecked")
public static <T> Single<T> never() {
return RxJavaPlugins.onAssembly((Single<T>) SingleNever.INSTANCE);
}
/**
* Signals success with 0L value after the given delay for each SingleObserver.
* <dl>
* <dt><b>Scheduler:</b></dt>
* <dd>{@code timer} operates by default on the {@code computation} {@link Scheduler}.</dd>
* </dl>
* @param delay the delay amount
* @param unit the time unit of the delay
* @return the new Single instance
* @since 2.0
*/
@CheckReturnValue
@SchedulerSupport(SchedulerSupport.COMPUTATION)
public static Single<Long> timer(long delay, TimeUnit unit) {
return timer(delay, unit, Schedulers.computation());
}
/**
* Signals success with 0L value after the given delay for each SingleObserver.
* <dl>
* <dt><b>Scheduler:</b></dt>
* <dd>you specify the {@link Scheduler} to signal on.</dd>
* </dl>
* @param delay the delay amount
* @param unit the time unit of the delay
* @param scheduler the scheduler where the single 0L will be emitted
* @return the new Single instance
* @throws NullPointerException
* if unit is null, or
* if scheduler is null
* @since 2.0
*/
@CheckReturnValue
@SchedulerSupport(SchedulerSupport.CUSTOM)
public static Single<Long> timer(final long delay, final TimeUnit unit, final Scheduler scheduler) {
ObjectHelper.requireNonNull(unit, "unit is null");
ObjectHelper.requireNonNull(scheduler, "scheduler is null");
return RxJavaPlugins.onAssembly(new SingleTimer(delay, unit, scheduler));
}
/**
* Compares two SingleSources and emits true if they emit the same value (compared via Object.equals).
* <dl>
* <dt><b>Scheduler:</b></dt>
* <dd>{@code equals} does not operate by default on a particular {@link Scheduler}.</dd>
* </dl>
* @param <T> the common value type
* @param first the first SingleSource instance
* @param second the second SingleSource instance
* @return the new Single instance
* @since 2.0
*/
@CheckReturnValue
@SchedulerSupport(SchedulerSupport.NONE)
public static <T> Single<Boolean> equals(final SingleSource<? extends T> first, final SingleSource<? extends T> second) { // NOPMD
ObjectHelper.requireNonNull(first, "first is null");
ObjectHelper.requireNonNull(second, "second is null");
return RxJavaPlugins.onAssembly(new SingleEquals<T>(first, second));
}
/**
* <strong>Advanced use only:</strong> creates a Single instance without
* any safeguards by using a callback that is called with a SingleObserver.
* <dl>
* <dt><b>Scheduler:</b></dt>
* <dd>{@code unsafeCreate} does not operate by default on a particular {@link Scheduler}.</dd>
* </dl>
* @param <T> the value type
* @param onSubscribe the function that is called with the subscribing SingleObserver
* @return the new Single instance
* @throws IllegalArgumentException if {@code source} is a subclass of {@code Single}; such
* instances don't need conversion and is possibly a port remnant from 1.x or one should use {@link #hide()}
* instead.
* @since 2.0
*/
@CheckReturnValue
@SchedulerSupport(SchedulerSupport.NONE)
public static <T> Single<T> unsafeCreate(SingleSource<T> onSubscribe) {
ObjectHelper.requireNonNull(onSubscribe, "onSubscribe is null");
if (onSubscribe instanceof Single) {
throw new IllegalArgumentException("unsafeCreate(Single) should be upgraded");
}
return RxJavaPlugins.onAssembly(new SingleFromUnsafeSource<T>(onSubscribe));
}
/**
* Allows using and disposing a resource while running a SingleSource instance generated from
* that resource (similar to a try-with-resources).
* <dl>
* <dt><b>Scheduler:</b></dt>
* <dd>{@code using} does not operate by default on a particular {@link Scheduler}.</dd>
* </dl>
* @param <T> the value type of the SingleSource generated
* @param <U> the resource type
* @param resourceSupplier the Callable called for each SingleObserver to generate a resource Object
* @param singleFunction the function called with the returned resource
* Object from {@code resourceSupplier} and should return a SingleSource instance
* to be run by the operator
* @param disposer the consumer of the generated resource that is called exactly once for
* that particular resource when the generated SingleSource terminates
* (successfully or with an error) or gets cancelled.
* @return the new Single instance
* @since 2.0
*/
@CheckReturnValue
@SchedulerSupport(SchedulerSupport.NONE)
public static <T, U> Single<T> using(Callable<U> resourceSupplier,
Function<? super U, ? extends SingleSource<? extends T>> singleFunction,
Consumer<? super U> disposer) {
return using(resourceSupplier, singleFunction, disposer, true);
}
/**
* Allows using and disposing a resource while running a SingleSource instance generated from
* that resource (similar to a try-with-resources).
* <dl>
* <dt><b>Scheduler:</b></dt>
* <dd>{@code using} does not operate by default on a particular {@link Scheduler}.</dd>
* </dl>
* @param <T> the value type of the SingleSource generated
* @param <U> the resource type
* @param resourceSupplier the Callable called for each SingleObserver to generate a resource Object
* @param singleFunction the function called with the returned resource
* Object from {@code resourceSupplier} and should return a SingleSource instance
* to be run by the operator
* @param disposer the consumer of the generated resource that is called exactly once for
* that particular resource when the generated SingleSource terminates
* (successfully or with an error) or gets cancelled.
* @param eager
* if true, the disposer is called before the terminal event is signalled
* if false, the disposer is called after the terminal event is delivered to downstream
* @return the new Single instance
* @since 2.0
*/
@CheckReturnValue
@SchedulerSupport(SchedulerSupport.NONE)
public static <T, U> Single<T> using(
final Callable<U> resourceSupplier,
final Function<? super U, ? extends SingleSource<? extends T>> singleFunction,
final Consumer<? super U> disposer,
final boolean eager) {
ObjectHelper.requireNonNull(resourceSupplier, "resourceSupplier is null");
ObjectHelper.requireNonNull(singleFunction, "singleFunction is null");