本文整理了Java中rx.Observable.firstOrDefault()方法的一些代码示例，展示了Observable.firstOrDefault()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。Observable.firstOrDefault()方法的具体详情如下：
包路径：rx.Observable
类名称：Observable
方法名：firstOrDefault

Observable.firstOrDefault介绍

[英]Returns an Observable that emits only the very first item emitted by the source Observable, or a default item if the source Observable completes without emitting anything.

Scheduler: firstOrDefault does not operate by default on a particular Scheduler.
[中]返回仅发射源可观测项发射的第一项的可观测项，或者如果源可观测项完成而不发射任何内容，则返回默认项。
调度程序：默认情况下，firstOrDefault不会在特定调度程序上运行。

代码示例

代码示例来源：origin: Netflix/EVCache

.doOnSuccess(fbData -> increment(fbClient.getServerGroupName(), _cacheName, "RETRY_" + ((fbData == null) ? "MISS" : "HIT")))
.toObservable()))
.firstOrDefault(null, fbData -> (fbData != null)).toSingle();

代码示例来源：origin: Netflix/EVCache

.doOnSuccess(fbData -> increment(fbClient.getServerGroupName(), _cacheName, "RETRY_" + ((fbData == null) ? "MISS" : "HIT")))
.toObservable()))
.firstOrDefault(null, fbData -> (fbData != null)).toSingle();

代码示例来源：origin: leeowenowen/rxjava-examples

@Override
 public void run() {
  Observable.range(1, 10).firstOrDefault(3).subscribe(new Action1<Integer>() {
   @Override
   public void call(Integer integer) {
    log(integer);
   }
  });
 }
});

代码示例来源：origin: org.zalando.paradox/paradox-nakadi-consumer-core

@Override
public Single<String> getContent(final EventTypeCursor cursor) {
  final Observable<HttpResponseChunk> request = getContent0(cursor, 1);
  return request.map(HttpResponseChunk::getContent).firstOrDefault(null).toSingle();
}

代码示例来源：origin: com.microsoft.azure/azure-mgmt-compute

/**
 * Retrieves encryption extension installed in the virtual machine, if the extension is
 * not installed then return an empty observable.
 *
 * @return an observable that emits the encryption extension installed in the virtual machine
 */
private Observable<VirtualMachineExtension> getEncryptionExtensionInstalledInVMAsync() {
  return virtualMachine.listExtensionsAsync()
      // firstOrDefault() is used intentionally here instead of first() to ensure
      // this method return empty observable if matching extension is not found.
      //
      .firstOrDefault(null, new Func1<VirtualMachineExtension, Boolean>() {
        @Override
        public Boolean call(final VirtualMachineExtension extension) {
          return extension.publisherName().equalsIgnoreCase(encryptionExtensionPublisher)
              && extension.typeName().equalsIgnoreCase(encryptionExtensionType());
        }
      }).flatMap(new Func1<VirtualMachineExtension, Observable<VirtualMachineExtension>>() {
        @Override
        public Observable<VirtualMachineExtension> call(VirtualMachineExtension extension) {
          if (extension == null) {
            return Observable.empty();
          }
          return Observable.just(extension);
        }
      });
}

代码示例来源：origin: com.netflix.rxjava/rxjava-core

/**
 * Returns the first item emitted by this {@code BlockingObservable} that matches a predicate, or a default
 * value if it emits no such items.
 *
 * @param defaultValue
 *            a default value to return if this {@code BlockingObservable} emits no matching items
 * @param predicate
 *            a predicate function to evaluate items emitted by this {@code BlockingObservable}
 * @return the first item emitted by this {@code BlockingObservable} that matches the predicate, or the
 *         default value if this {@code BlockingObservable} emits no matching items
 * @see <a href="https://github.com/ReactiveX/RxJava/wiki/Blocking-Observable-Operators#first-and-firstordefault">RxJava Wiki: firstOrDefault()</a>
 * @see <a href="http://msdn.microsoft.com/en-us/library/hh229759.aspx">MSDN: Observable.FirstOrDefault</a>
 */
public T firstOrDefault(T defaultValue, Func1<? super T, Boolean> predicate) {
  return blockForSingle(o.filter(predicate).map(Functions.<T>identity()).firstOrDefault(defaultValue));
}

代码示例来源：origin: com.netflix.rxjava/rxjava-core

/**
 * Returns the first item emitted by this {@code BlockingObservable}, or a default value if it emits no
 * items.
 *
 * @param defaultValue
 *            a default value to return if this {@code BlockingObservable} emits no items
 * @return the first item emitted by this {@code BlockingObservable}, or the default value if it emits no
 *         items
 * @see <a href="https://github.com/ReactiveX/RxJava/wiki/Blocking-Observable-Operators#first-and-firstordefault">RxJava Wiki: firstOrDefault()</a>
 * @see <a href="http://msdn.microsoft.com/en-us/library/hh229320.aspx">MSDN: Observable.FirstOrDefault</a>
 */
public T firstOrDefault(T defaultValue) {
  return blockForSingle(o.map(Functions.<T>identity()).firstOrDefault(defaultValue));
}

代码示例来源：origin: Azure/azure-libraries-for-java

/**
 * Retrieves encryption extension installed in the virtual machine, if the extension is
 * not installed then return an empty observable.
 *
 * @return an observable that emits the encryption extension installed in the virtual machine
 */
private Observable<VirtualMachineExtension> getEncryptionExtensionInstalledInVMAsync() {
  return virtualMachine.listExtensionsAsync()
      // firstOrDefault() is used intentionally here instead of first() to ensure
      // this method return empty observable if matching extension is not found.
      //
      .firstOrDefault(null, new Func1<VirtualMachineExtension, Boolean>() {
        @Override
        public Boolean call(final VirtualMachineExtension extension) {
          return extension.publisherName().equalsIgnoreCase(encryptionExtensionPublisher)
              && extension.typeName().equalsIgnoreCase(encryptionExtensionType());
        }
      }).flatMap(new Func1<VirtualMachineExtension, Observable<VirtualMachineExtension>>() {
        @Override
        public Observable<VirtualMachineExtension> call(VirtualMachineExtension extension) {
          if (extension == null) {
            return Observable.empty();
          }
          return Observable.just(extension);
        }
      });
}

代码示例来源：origin: org.zalando.paradox/paradox-nakadi-consumer-core

@Override
public Single<String> getEvent(final EventTypeCursor cursor) {
  final Observable<HttpResponseChunk> request = getContent0(cursor, 1);
  return request.map(chunk -> getEvent0(chunk.getContent(), cursor.getEventType())).firstOrDefault(null)
         .toSingle();
}

代码示例来源：origin: org.zalando.paradox/paradox-nakadi-consumer-core

@Override
public Single<List<NakadiPartition>> getPartitions(final EventType eventType) {
  final HttpGetPartitions httpGetPartitions = new HttpGetPartitions(nakadiUrl, eventType);
  final Observable<HttpResponseChunk> request = new RxHttpRequest(partitionsTimeoutMillis,
      authorizationValueProvider).createRequest(httpGetPartitions);
  return request.filter(chunk -> {
           checkArgument(chunk.getStatusCode() == 200,
             "Get partitions for event [%s] , result [%s / %s]", eventType, chunk.getStatusCode(),
             chunk.getContent());
           return true;
         }).map(chunk -> getPartitions(chunk.getContent())).firstOrDefault(Collections.emptyList())
         .toSingle();
}

代码示例来源：origin: com.couchbase.client/java-client

.getFromReplica(id, ReplicaMode.ALL, target)
.timeout(replicaTimeout, TimeUnit.MILLISECONDS)
.firstOrDefault(null)
.filter(new Func1<D, Boolean>() {
  @Override

代码示例来源：origin: akarnokd/akarnokd-misc

.observeOn(uiScheduler)
.firstOrDefault(defaultList, items -> items != null && !items.isEmpty())
.subscribe(subscriber);