/*
 * Copyright (c) 2011-2017 Pivotal Software Inc, All Rights Reserved.
 *
 * 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
 *
 *       https://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 reactor.core.publisher;

import java.util.Objects;

import org.reactivestreams.Subscription;
import reactor.core.CoreSubscriber;
import reactor.core.Fuseable;
import reactor.util.annotation.Nullable;

Emits only the element at the given index position or signals a default value if specified or IndexOutOfBoundsException if the sequence is shorter.
Type parameters:
  • <T> – the value type
See Also:
/** * Emits only the element at the given index position or signals a * default value if specified or IndexOutOfBoundsException if the sequence is shorter. * * @param <T> the value type * @see <a href="https://github.com/reactor/reactive-streams-commons">Reactive-Streams-Commons</a> */
final class MonoElementAt<T> extends MonoFromFluxOperator<T, T> implements Fuseable { final long index; final T defaultValue; MonoElementAt(Flux<? extends T> source, long index) { super(source); if (index < 0) { throw new IndexOutOfBoundsException("index >= required but it was " + index); } this.index = index; this.defaultValue = null; } MonoElementAt(Flux<? extends T> source, long index, T defaultValue) { super(source); if (index < 0) { throw new IndexOutOfBoundsException("index >= required but it was " + index); } this.index = index; this.defaultValue = Objects.requireNonNull(defaultValue, "defaultValue"); } @Override public CoreSubscriber<? super T> subscribeOrReturn(CoreSubscriber<? super T> actual) { return new ElementAtSubscriber<>(actual, index, defaultValue); } @Override public Object scanUnsafe(Attr key) { if (key == Attr.RUN_STYLE) return Attr.RunStyle.SYNC; return super.scanUnsafe(key); } static final class ElementAtSubscriber<T> extends Operators.MonoSubscriber<T, T> { final T defaultValue; long index; Subscription s; boolean done; ElementAtSubscriber(CoreSubscriber<? super T> actual, long index, T defaultValue) { super(actual); this.index = index; this.defaultValue = defaultValue; } @Override @Nullable public Object scanUnsafe(Attr key) { if (key == Attr.TERMINATED) return done; if (key == Attr.PARENT) return s; if (key == Attr.RUN_STYLE) return Attr.RunStyle.SYNC; return super.scanUnsafe(key); } @Override public void request(long n) { super.request(n); if (n > 0L) { s.request(Long.MAX_VALUE); } } @Override public void cancel() { super.cancel(); s.cancel(); } @Override public void onSubscribe(Subscription s) { if (Operators.validate(this.s, s)) { this.s = s; actual.onSubscribe(this); } } @Override public void onNext(T t) { if (done) { Operators.onNextDropped(t, actual.currentContext()); return; } long i = index; if (i == 0) { done = true; s.cancel(); actual.onNext(t); actual.onComplete(); return; } index = i - 1; Operators.onDiscard(t, actual.currentContext()); //FIXME cache currentcontext } @Override public void onError(Throwable t) { if (done) { Operators.onErrorDropped(t, actual.currentContext()); return; } done = true; actual.onError(t); } @Override public void onComplete() { if (done) { return; } done = true; if(defaultValue != null) { complete(defaultValue); } else{ actual.onError(Operators.onOperatorError(new IndexOutOfBoundsException(), actual.currentContext())); } } } }