3.x: [Java 8] Add Observable operators + cleanup

src/main/java/io/reactivex/rxjava3/internal/jdk8/FlowableFromStream.java

@@ -69,7 +69,7 @@ public static <T> void subscribeStream(Subscriber<? super T> s, Stream<T> stream
         }
 
         if (s instanceof ConditionalSubscriber) {
-            s.onSubscribe(new StreamConditionalSubscription<T>((ConditionalSubscriber<? super T>)s, iterator, stream));
+            s.onSubscribe(new StreamConditionalSubscription<>((ConditionalSubscriber<? super T>)s, iterator, stream));
         } else {
             s.onSubscribe(new StreamSubscription<>(s, iterator, stream));
         }
@@ -147,15 +147,23 @@ public T poll() {
                 once = true;
             } else {
                 if (!iterator.hasNext()) {
+                    clear();
                     return null;
                 }
             }
-            return Objects.requireNonNull(iterator.next(), "Iterator.next() returned a null value");
+            return Objects.requireNonNull(iterator.next(), "The Stream's Iterator.next() returned a null value");
         }
 
         @Override
         public boolean isEmpty() {
-            return iterator == null || !iterator.hasNext();
+            Iterator<T> it = iterator;
+            if (it != null) {
+                if (!once || it.hasNext()) {
+                    return false;
+                }
+                clear();
+            }
+            return true;
         }
 
         @Override

src/main/java/io/reactivex/rxjava3/internal/jdk8/ObservableCollectWithCollector.java

@@ -0,0 +1,151 @@
+/**
+ * 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.rxjava3.internal.jdk8;
+
+import java.util.Objects;
+import java.util.function.*;
+import java.util.stream.Collector;
+
+import io.reactivex.rxjava3.annotations.NonNull;
+import io.reactivex.rxjava3.core.*;
+import io.reactivex.rxjava3.disposables.Disposable;
+import io.reactivex.rxjava3.exceptions.Exceptions;
+import io.reactivex.rxjava3.internal.disposables.*;
+import io.reactivex.rxjava3.internal.observers.DeferredScalarDisposable;
+import io.reactivex.rxjava3.plugins.RxJavaPlugins;
+
+/**
+ * Collect items into a container defined by a Stream {@link Collector} callback set.
+ *
+ * @param <T> the upstream value type
+ * @param <A> the intermediate accumulator type
+ * @param <R> the result type
+ * @since 3.0.0
+ */
+public final class ObservableCollectWithCollector<T, A, R> extends Observable<R> {
+
+    final Observable<T> source;
+
+    final Collector<T, A, R> collector;
+
+    public ObservableCollectWithCollector(Observable<T> source, Collector<T, A, R> collector) {
+        this.source = source;
+        this.collector = collector;
+    }
+
+    @Override
+    protected void subscribeActual(@NonNull Observer<? super R> observer) {
+        A container;
+        BiConsumer<A, T> accumulator;
+        Function<A, R> finisher;
+
+        try {
+            container = collector.supplier().get();
+            accumulator = collector.accumulator();
+            finisher = collector.finisher();
+        } catch (Throwable ex) {
+            Exceptions.throwIfFatal(ex);
+            EmptyDisposable.error(ex, observer);
+            return;
+        }
+
+        source.subscribe(new CollectorObserver<>(observer, container, accumulator, finisher));
+    }
+
+    static final class CollectorObserver<T, A, R>
+    extends DeferredScalarDisposable<R>
+    implements Observer<T> {
+
+        private static final long serialVersionUID = -229544830565448758L;
+
+        final BiConsumer<A, T> accumulator;
+
+        final Function<A, R> finisher;
+
+        Disposable upstream;
+
+        boolean done;
+
+        A container;
+
+        CollectorObserver(Observer<? super R> downstream, A container, BiConsumer<A, T> accumulator, Function<A, R> finisher) {
+            super(downstream);
+            this.container = container;
+            this.accumulator = accumulator;
+            this.finisher = finisher;
+        }
+
+        @Override
+        public void onSubscribe(@NonNull Disposable d) {
+            if (DisposableHelper.validate(this.upstream, d)) {
+                this.upstream = d;
+
+                downstream.onSubscribe(this);
+            }
+        }
+
+        @Override
+        public void onNext(T t) {
+            if (done) {
+                return;
+            }
+            try {
+                accumulator.accept(container, t);
+            } catch (Throwable ex) {
+                Exceptions.throwIfFatal(ex);
+                upstream.dispose();
+                onError(ex);
+            }
+        }
+
+        @Override
+        public void onError(Throwable t) {
+            if (done) {
+                RxJavaPlugins.onError(t);
+            } else {
+                done = true;
+                upstream = DisposableHelper.DISPOSED;
+                this.container = null;
+                downstream.onError(t);
+            }
+        }
+
+        @Override
+        public void onComplete() {
+            if (done) {
+                return;
+            }
+
+            done = true;
+            upstream = DisposableHelper.DISPOSED;
+            A container = this.container;
+            this.container = null;
+            R result;
+            try {
+                result = Objects.requireNonNull(finisher.apply(container), "The finisher returned a null value");
+            } catch (Throwable ex) {
+                Exceptions.throwIfFatal(ex);
+                downstream.onError(ex);
+                return;
+            }
+
+            complete(result);
+        }
+
+        @Override
+        public void dispose() {
+            super.dispose();
+            upstream.dispose();
+        }
+    }
+}

src/main/java/io/reactivex/rxjava3/internal/jdk8/ObservableCollectWithCollectorSingle.java

@@ -0,0 +1,159 @@
+/**
+ * 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.rxjava3.internal.jdk8;
+
+import java.util.Objects;
+import java.util.function.*;
+import java.util.stream.Collector;
+
+import io.reactivex.rxjava3.annotations.NonNull;
+import io.reactivex.rxjava3.core.*;
+import io.reactivex.rxjava3.disposables.Disposable;
+import io.reactivex.rxjava3.exceptions.Exceptions;
+import io.reactivex.rxjava3.internal.disposables.*;
+import io.reactivex.rxjava3.internal.fuseable.FuseToObservable;
+import io.reactivex.rxjava3.plugins.RxJavaPlugins;
+
+/**
+ * Collect items into a container defined by a Stream {@link Collector} callback set.
+ *
+ * @param <T> the upstream value type
+ * @param <A> the intermediate accumulator type
+ * @param <R> the result type
+ * @since 3.0.0
+ */
+public final class ObservableCollectWithCollectorSingle<T, A, R> extends Single<R> implements FuseToObservable<R> {
+
+    final Observable<T> source;
+
+    final Collector<T, A, R> collector;
+
+    public ObservableCollectWithCollectorSingle(Observable<T> source, Collector<T, A, R> collector) {
+        this.source = source;
+        this.collector = collector;
+    }
+
+    @Override
+    public Observable<R> fuseToObservable() {
+        return new ObservableCollectWithCollector<>(source, collector);
+    }
+
+    @Override
+    protected void subscribeActual(@NonNull SingleObserver<? super R> observer) {
+        A container;
+        BiConsumer<A, T> accumulator;
+        Function<A, R> finisher;
+
+        try {
+            container = collector.supplier().get();
+            accumulator = collector.accumulator();
+            finisher = collector.finisher();
+        } catch (Throwable ex) {
+            Exceptions.throwIfFatal(ex);
+            EmptyDisposable.error(ex, observer);
+            return;
+        }
+
+        source.subscribe(new CollectorSingleObserver<>(observer, container, accumulator, finisher));
+    }
+
+    static final class CollectorSingleObserver<T, A, R> implements Observer<T>, Disposable {
+
+        final SingleObserver<? super R> downstream;
+
+        final BiConsumer<A, T> accumulator;
+
+        final Function<A, R> finisher;
+
+        Disposable upstream;
+
+        boolean done;
+
+        A container;
+
+        CollectorSingleObserver(SingleObserver<? super R> downstream, A container, BiConsumer<A, T> accumulator, Function<A, R> finisher) {
+            this.downstream = downstream;
+            this.container = container;
+            this.accumulator = accumulator;
+            this.finisher = finisher;
+        }
+
+        @Override
+        public void onSubscribe(@NonNull Disposable d) {
+            if (DisposableHelper.validate(this.upstream, d)) {
+                this.upstream = d;
+
+                downstream.onSubscribe(this);
+            }
+        }
+
+        @Override
+        public void onNext(T t) {
+            if (done) {
+                return;
+            }
+            try {
+                accumulator.accept(container, t);
+            } catch (Throwable ex) {
+                Exceptions.throwIfFatal(ex);
+                upstream.dispose();
+                onError(ex);
+            }
+        }
+
+        @Override
+        public void onError(Throwable t) {
+            if (done) {
+                RxJavaPlugins.onError(t);
+            } else {
+                done = true;
+                upstream = DisposableHelper.DISPOSED;
+                this.container = null;
+                downstream.onError(t);
+            }
+        }
+
+        @Override
+        public void onComplete() {
+            if (done) {
+                return;
+            }
+
+            done = true;
+            upstream = DisposableHelper.DISPOSED;
+            A container = this.container;
+            this.container = null;
+            R result;
+            try {
+                result = Objects.requireNonNull(finisher.apply(container), "The finisher returned a null value");
+            } catch (Throwable ex) {
+                Exceptions.throwIfFatal(ex);
+                downstream.onError(ex);
+                return;
+            }
+
+            downstream.onSuccess(result);
+        }
+
+        @Override
+        public void dispose() {
+            upstream.dispose();
+            upstream = DisposableHelper.DISPOSED;
+        }
+
+        @Override
+        public boolean isDisposed() {
+            return upstream == DisposableHelper.DISPOSED;
+        }
+    }
+}

src/main/java/io/reactivex/rxjava3/internal/jdk8/ObservableFirstStageObserver.java

@@ -0,0 +1,51 @@
+/**
+ * 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.rxjava3.internal.jdk8;
+
+import java.util.NoSuchElementException;
+
+/**
+ * Signals the first element of the source via the underlying CompletableFuture,
+ * signals the a default item if the upstream is empty or signals {@link NoSuchElementException}.
+ *
+ * @param <T> the element type
+ * @since 3.0.0
+ */
+public final class ObservableFirstStageObserver<T> extends ObservableStageObserver<T> {
+
+    final boolean hasDefault;
+
+    final T defaultItem;
+
+    public ObservableFirstStageObserver(boolean hasDefault, T defaultItem) {
+        this.hasDefault = hasDefault;
+        this.defaultItem = defaultItem;
+    }
+
+    @Override
+    public void onNext(T t) {
+        complete(t);
+    }
+
+    @Override
+    public void onComplete() {
+        if (!isDone()) {
+            clear();
+            if (hasDefault) {
+                complete(defaultItem);
+            } else {
+                completeExceptionally(new NoSuchElementException());
+            }
+        }
+    }
+}