io.reactivex.Flowable.firstElement()方法的使用及代码示例

x33g5p2x  于2022-01-19 转载在 其他  
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本文整理了Java中io.reactivex.Flowable.firstElement()方法的一些代码示例，展示了Flowable.firstElement()的具体用法。这些代码示例主要来源于Github/Stackoverflow/Maven等平台，是从一些精选项目中提取出来的代码，具有较强的参考意义，能在一定程度帮忙到你。Flowable.firstElement()方法的具体详情如下：
包路径：io.reactivex.Flowable
类名称：Flowable
方法名：firstElement

Flowable.firstElement介绍

[英]Returns a Maybe that emits only the very first item emitted by this Flowable or completes if this Flowable is empty.

Backpressure: The operator honors backpressure from downstream and consumes the source Publisher in an unbounded manner (i.e., without applying backpressure). Scheduler: firstElement does not operate by default on a particular Scheduler.
[中]返回一个值，该值仅发出此可流动项发出的第一个项，或者如果此可流动项为空，则返回完成。
背压：操作员接受来自下游的背压，并以无限制的方式（即不施加背压）消耗源发布服务器。Scheduler:firstElement默认情况下不会在特定的计划程序上运行。

代码示例

代码示例来源：origin: ReactiveX/RxJava

  1. @Override
  2. public Publisher<Integer> createPublisher(final long elements) {
  3.   return
  4.       Flowable.range(1, 10).firstElement().toFlowable()
  5.     ;
  6. }

代码示例来源：origin: ReactiveX/RxJava

  1. @Test
  2. public void testFirstOfNoneFlowable() {
  3.   Flowable<Integer> flowable = Flowable.empty();
  4.   flowable.firstElement().toFlowable().subscribe(w);
  5.   verify(w, never()).onNext(anyInt());
  6.   verify(w).onComplete();
  7.   verify(w, never()).onError(any(Throwable.class));
  8. }

代码示例来源：origin: ReactiveX/RxJava

  1. @Test
  2. public void testFirstWithEmpty() {
  3.   Maybe<Integer> maybe = Flowable.<Integer> empty().firstElement();
  4.   maybe.subscribe(wm);
  5.   InOrder inOrder = inOrder(wm);
  6.   inOrder.verify(wm).onComplete();
  7.   inOrder.verify(wm, never()).onError(any(Throwable.class));
  8.   inOrder.verifyNoMoreInteractions();
  9. }

代码示例来源：origin: ReactiveX/RxJava

  1. @Test
  2. public void testFirstOfNone() {
  3.   Flowable<Integer> flowable = Flowable.empty();
  4.   flowable.firstElement().subscribe(wm);
  5.   verify(wm, never()).onSuccess(anyInt());
  6.   verify(wm).onComplete();
  7.   verify(wm, never()).onError(isA(NoSuchElementException.class));
  8. }

代码示例来源：origin: ReactiveX/RxJava

  1. @Test
  2. public void testFirst() {
  3.   Maybe<Integer> maybe = Flowable.just(1, 2, 3).firstElement();
  4.   maybe.subscribe(wm);
  5.   InOrder inOrder = inOrder(wm);
  6.   inOrder.verify(wm, times(1)).onSuccess(1);
  7.   inOrder.verifyNoMoreInteractions();
  8. }

代码示例来源：origin: ReactiveX/RxJava

  1. @Test
  2. public void testFirstWithPredicateOfNoneMatchingThePredicate() {
  3.   Flowable<Integer> flowable = Flowable.just(1, 3, 5, 7, 9, 7, 5, 3, 1);
  4.   flowable.filter(IS_EVEN).firstElement().subscribe(wm);
  5.   verify(wm, never()).onSuccess(anyInt());
  6.   verify(wm, times(1)).onComplete();
  7.   verify(wm, never()).onError(isA(NoSuchElementException.class));
  8. }

代码示例来源：origin: ReactiveX/RxJava

  1. @Test
  2. public void testFirstWithOneElement() {
  3.   Maybe<Integer> maybe = Flowable.just(1).firstElement();
  4.   maybe.subscribe(wm);
  5.   InOrder inOrder = inOrder(wm);
  6.   inOrder.verify(wm, times(1)).onSuccess(1);
  7.   inOrder.verifyNoMoreInteractions();
  8. }

代码示例来源：origin: ReactiveX/RxJava

  1. @Test
  2. public void testFirstWithPredicateOfNoneMatchingThePredicateFlowable() {
  3.   Flowable<Integer> flowable = Flowable.just(1, 3, 5, 7, 9, 7, 5, 3, 1);
  4.   flowable.filter(IS_EVEN).firstElement().toFlowable().subscribe(w);
  5.   verify(w, never()).onNext(anyInt());
  6.   verify(w).onComplete();
  7.   verify(w, never()).onError(any(Throwable.class));
  8. }

代码示例来源：origin: ReactiveX/RxJava

  1. @Test
  2. public void testFirstWithOneElementFlowable() {
  3.   Flowable<Integer> flowable = Flowable.just(1).firstElement().toFlowable();
  4.   Subscriber<Integer> subscriber = TestHelper.mockSubscriber();
  5.   flowable.subscribe(subscriber);
  6.   InOrder inOrder = inOrder(subscriber);
  7.   inOrder.verify(subscriber, times(1)).onNext(1);
  8.   inOrder.verify(subscriber, times(1)).onComplete();
  9.   inOrder.verifyNoMoreInteractions();
  10. }

代码示例来源：origin: ReactiveX/RxJava

  1. @Test
  2. public void testFirstWithEmptyFlowable() {
  3.   Flowable<Integer> flowable = Flowable.<Integer> empty().firstElement().toFlowable();
  4.   Subscriber<Integer> subscriber = TestHelper.mockSubscriber();
  5.   flowable.subscribe(subscriber);
  6.   InOrder inOrder = inOrder(subscriber);
  7.   inOrder.verify(subscriber).onComplete();
  8.   inOrder.verify(subscriber, never()).onError(any(Throwable.class));
  9.   inOrder.verifyNoMoreInteractions();
  10. }

代码示例来源：origin: ReactiveX/RxJava

  1. @Test
  2. public void testFirstFlowable() {
  3.   Flowable<Integer> flowable = Flowable.just(1, 2, 3).firstElement().toFlowable();
  4.   Subscriber<Integer> subscriber = TestHelper.mockSubscriber();
  5.   flowable.subscribe(subscriber);
  6.   InOrder inOrder = inOrder(subscriber);
  7.   inOrder.verify(subscriber, times(1)).onNext(1);
  8.   inOrder.verify(subscriber, times(1)).onComplete();
  9.   inOrder.verifyNoMoreInteractions();
  10. }

代码示例来源：origin: ReactiveX/RxJava

  1. @Test
  2. public void testFirstWithPredicateAndEmpty() {
  3.   Maybe<Integer> maybe = Flowable.just(1)
  4.       .filter(new Predicate<Integer>() {
  5.         @Override
  6.         public boolean test(Integer t1) {
  7.           return t1 % 2 == 0;
  8.         }
  9.       })
  10.       .firstElement();
  11.   maybe.subscribe(wm);
  12.   InOrder inOrder = inOrder(wm);
  13.   inOrder.verify(wm).onComplete();
  14.   inOrder.verify(wm, never()).onError(any(Throwable.class));
  15.   inOrder.verifyNoMoreInteractions();
  16. }

代码示例来源：origin: ReactiveX/RxJava

  1. @Test
  2. public void testFirstWithPredicate() {
  3.   Maybe<Integer> maybe = Flowable.just(1, 2, 3, 4, 5, 6)
  4.       .filter(new Predicate<Integer>() {
  5.         @Override
  6.         public boolean test(Integer t1) {
  7.           return t1 % 2 == 0;
  8.         }
  9.       })
  10.       .firstElement();
  11.   maybe.subscribe(wm);
  12.   InOrder inOrder = inOrder(wm);
  13.   inOrder.verify(wm, times(1)).onSuccess(2);
  14.   inOrder.verifyNoMoreInteractions();
  15. }

代码示例来源：origin: ReactiveX/RxJava

  1. @Test
  2. public void testFirstWithPredicateAndOneElement() {
  3.   Maybe<Integer> maybe = Flowable.just(1, 2)
  4.       .filter(new Predicate<Integer>() {
  5.         @Override
  6.         public boolean test(Integer t1) {
  7.           return t1 % 2 == 0;
  8.         }
  9.       })
  10.       .firstElement();
  11.   maybe.subscribe(wm);
  12.   InOrder inOrder = inOrder(wm);
  13.   inOrder.verify(wm, times(1)).onSuccess(2);
  14.   inOrder.verifyNoMoreInteractions();
  15. }

代码示例来源：origin: ReactiveX/RxJava

  1. @Test
  2. public void testFirstWithPredicateAndOneElementFlowable() {
  3.   Flowable<Integer> flowable = Flowable.just(1, 2)
  4.       .filter(new Predicate<Integer>() {
  5.         @Override
  6.         public boolean test(Integer t1) {
  7.           return t1 % 2 == 0;
  8.         }
  9.       })
  10.       .firstElement().toFlowable();
  11.   Subscriber<Integer> subscriber = TestHelper.mockSubscriber();
  12.   flowable.subscribe(subscriber);
  13.   InOrder inOrder = inOrder(subscriber);
  14.   inOrder.verify(subscriber, times(1)).onNext(2);
  15.   inOrder.verify(subscriber, times(1)).onComplete();
  16.   inOrder.verifyNoMoreInteractions();
  17. }

代码示例来源：origin: ReactiveX/RxJava

  1. @Test
  2. public void testFirstWithPredicateAndEmptyFlowable() {
  3.   Flowable<Integer> flowable = Flowable.just(1)
  4.       .filter(new Predicate<Integer>() {
  5.         @Override
  6.         public boolean test(Integer t1) {
  7.           return t1 % 2 == 0;
  8.         }
  9.       })
  10.       .firstElement().toFlowable();
  11.   Subscriber<Integer> subscriber = TestHelper.mockSubscriber();
  12.   flowable.subscribe(subscriber);
  13.   InOrder inOrder = inOrder(subscriber);
  14.   inOrder.verify(subscriber).onComplete();
  15.   inOrder.verify(subscriber, never()).onError(any(Throwable.class));
  16.   inOrder.verifyNoMoreInteractions();
  17. }

代码示例来源：origin: ReactiveX/RxJava

  1. @SuppressWarnings("unchecked")
  2. @Test
  3. public void noSubsequentSubscription() {
  4.   final int[] calls = { 0 };
  5.   Maybe<Integer> source = Maybe.create(new MaybeOnSubscribe<Integer>() {
  6.     @Override
  7.     public void subscribe(MaybeEmitter<Integer> s) throws Exception {
  8.       calls[0]++;
  9.       s.onSuccess(1);
  10.     }
  11.   });
  12.   Maybe.concat(Arrays.asList(source, source)).firstElement()
  13.   .test()
  14.   .assertResult(1);
  15.   assertEquals(1, calls[0]);
  16. }

代码示例来源：origin: ReactiveX/RxJava

  1. @SuppressWarnings("unchecked")
  2. @Test
  3. public void noSubsequentSubscriptionDelayErrorIterable() {
  4.   final int[] calls = { 0 };
  5.   Flowable<Integer> source = Flowable.create(new FlowableOnSubscribe<Integer>() {
  6.     @Override
  7.     public void subscribe(FlowableEmitter<Integer> s) throws Exception {
  8.       calls[0]++;
  9.       s.onNext(1);
  10.       s.onComplete();
  11.     }
  12.   }, BackpressureStrategy.MISSING);
  13.   Flowable.concatDelayError(Arrays.asList(source, source)).firstElement()
  14.   .test()
  15.   .assertResult(1);
  16.   assertEquals(1, calls[0]);
  17. }

代码示例来源：origin: ReactiveX/RxJava

  1. @SuppressWarnings("unchecked")
  2.   @Test
  3.   public void noSubsequentSubscriptionDelayError() {
  4.     final int[] calls = { 0 };
  6.     Maybe<Integer> source = Maybe.create(new MaybeOnSubscribe<Integer>() {
  7.       @Override
  8.       public void subscribe(MaybeEmitter<Integer> s) throws Exception {
  9.         calls[0]++;
  10.         s.onSuccess(1);
  11.       }
  12.     });
  14.     Maybe.concatArrayDelayError(source, source).firstElement()
  15.     .test()
  16.     .assertResult(1);
  18.     assertEquals(1, calls[0]);
  19.   }
  20. }

代码示例来源：origin: ReactiveX/RxJava

  1. @SuppressWarnings("unchecked")
  2. @Test
  3. public void noSubsequentSubscription() {
  4.   final int[] calls = { 0 };
  5.   Single<Integer> source = Single.create(new SingleOnSubscribe<Integer>() {
  6.     @Override
  7.     public void subscribe(SingleEmitter<Integer> s) throws Exception {
  8.       calls[0]++;
  9.       s.onSuccess(1);
  10.     }
  11.   });
  12.   Single.concatArray(source, source).firstElement()
  13.   .test()
  14.   .assertResult(1);
  15.   assertEquals(1, calls[0]);
  16. }

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