Java Stream.spliterator方法代码示例

import java.util.stream.Stream; //导入方法依赖的package包/类
/**
 * Returns a {@link Stream} containing the elements of the first stream, followed by the elements
 * of the second stream, and so on.
 *
 * <p>This is equivalent to {@code Stream.of(streams).flatMap(stream -> stream)}, but the returned
 * stream may perform better.
 *
 * @see Stream#concat(Stream, Stream)
 */
@SafeVarargs
public static <T> Stream<T> concat(Stream<? extends T>... streams) {
  // TODO(lowasser): consider an implementation that can support SUBSIZED
  boolean isParallel = false;
  int characteristics = Spliterator.ORDERED | Spliterator.SIZED | Spliterator.NONNULL;
  long estimatedSize = 0L;
  ImmutableList.Builder<Spliterator<? extends T>> splitrsBuilder =
      new ImmutableList.Builder<>(streams.length);
  for (Stream<? extends T> stream : streams) {
    isParallel |= stream.isParallel();
    Spliterator<? extends T> splitr = stream.spliterator();
    splitrsBuilder.add(splitr);
    characteristics &= splitr.characteristics();
    estimatedSize = LongMath.saturatedAdd(estimatedSize, splitr.estimateSize());
  }
  return StreamSupport.stream(
      CollectSpliterators.flatMap(
          splitrsBuilder.build().spliterator(),
          splitr -> (Spliterator<T>) splitr,
          characteristics,
          estimatedSize),
      isParallel);
}
 

import java.util.stream.Stream; //导入方法依赖的package包/类
public static <T> Stream<T> distinct(Stream<T> src, Comparator<T> cmp) {
    Spliterator<T> iter = src.spliterator();
    Spliterator<T> res = new AbstractSpliterator<T>(Long.MAX_VALUE, Spliterator.ORDERED ) {
        // ArrayList<T> distinctData = new ArrayList<>();
        TreeSet<T> distinctData = new TreeSet<>(cmp);
        @Override
        public boolean tryAdvance(Consumer<? super T> action) {
            return iter.tryAdvance( item -> {
                // Versão 1: if (!contains(distinctData, cmp, item)) {
                // Versão 2: if(!distinctData.stream().anyMatch(e -> cmp.compare(e, item) == 0)) {
                // Versão 3:
                if (!distinctData.contains(item)) {
                    distinctData.add(item);
                    action.accept(item);
                }
            });
        }
    };
    return StreamSupport.stream(res, false);
}
 

import java.util.stream.Stream; //导入方法依赖的package包/类
/**
 * Returns a stream in which each element is the result of passing the corresponding elementY of
 * each of {@code streamA} and {@code streamB} to {@code function}.
 *
 * <p>For example:
 *
 * <pre>{@code
 * Streams.zip(
 *   Stream.of("foo1", "foo2", "foo3"),
 *   Stream.of("bar1", "bar2"),
 *   (arg1, arg2) -> arg1 + ":" + arg2)
 * }</pre>
 *
 * <p>will return {@code Stream.of("foo1:bar1", "foo2:bar2")}.
 *
 * <p>The resulting stream will only be as long as the shorter of the two input streams; if one
 * stream is longer, its extra elements will be ignored.
 *
 * <p>Note that if you are calling {@link Stream#forEach} on the resulting stream, you might want
 * to consider using {@link #forEachPair} instead of this method.
 *
 * <p><b>Performance note:</b> The resulting stream is not <a
 * href="http://gee.cs.oswego.edu/dl/html/StreamParallelGuidance.html">efficiently splittable</a>.
 * This may harm parallel performance.
 */
public static <A, B, R> Stream<R> zip(
    Stream<A> streamA, Stream<B> streamB, BiFunction<? super A, ? super B, R> function) {
  checkNotNull(streamA);
  checkNotNull(streamB);
  checkNotNull(function);
  boolean isParallel = streamA.isParallel() || streamB.isParallel(); // same as Stream.concat
  Spliterator<A> splitrA = streamA.spliterator();
  Spliterator<B> splitrB = streamB.spliterator();
  int characteristics =
      splitrA.characteristics()
          & splitrB.characteristics()
          & (Spliterator.SIZED | Spliterator.ORDERED);
  Iterator<A> itrA = Spliterators.iterator(splitrA);
  Iterator<B> itrB = Spliterators.iterator(splitrB);
  return StreamSupport.stream(
      new AbstractSpliterator<R>(
          Math.min(splitrA.estimateSize(), splitrB.estimateSize()), characteristics) {
        @Override
        public boolean tryAdvance(Consumer<? super R> action) {
          if (itrA.hasNext() && itrB.hasNext()) {
            action.accept(function.apply(itrA.next(), itrB.next()));
            return true;
          }
          return false;
        }
      },
      isParallel);
}
 

import java.util.stream.Stream; //导入方法依赖的package包/类
private static <T> Stream<T> concat(Stream<T> first, Stream<T> second) {
    Spliterator<T> iter1 = first.spliterator();
    Spliterator<T> iter2 = second.spliterator();
    Spliterator<T> iter = new AbstractSpliterator<T>(Long.MAX_VALUE, Spliterator.ORDERED) {
        boolean firstFinished = false;
        @Override
        public boolean tryAdvance(Consumer<? super T> action) {
            if(!firstFinished && iter1.tryAdvance(action)) return true;
            firstFinished = true;
            return iter2.tryAdvance(action);
        }
    };
    return StreamSupport.stream(iter, false);
}
 

import java.util.stream.Stream; //导入方法依赖的package包/类
public static <T> Stream<T> filterEvenLine(Stream<T> src) {
    Spliterator<T> iter = src.spliterator();
    Spliterator<T> res = new AbstractSpliterator<T>(Long.MAX_VALUE, Spliterator.ORDERED ) {
        @Override
        public boolean tryAdvance(Consumer<? super T> action) {
            return iter.tryAdvance(item -> {})
                    ? iter.tryAdvance(action)
                    : false;
        }
    };
    return StreamSupport.stream(res, false);
}
 

import java.util.stream.Stream; //导入方法依赖的package包/类
public static <T> Stream<T> distinct(Stream<T> src, Comparator<T> cmp) {
    Spliterator<T> iter = src.spliterator();
    Spliterator<T> res = new AbstractSpliterator<T>(Long.MAX_VALUE, Spliterator.ORDERED ) {
        @Override
        public boolean tryAdvance(Consumer<? super T> action) {
            return false;
        }
    };
    return StreamSupport.stream(res, false);
}
 

import java.util.stream.Stream; //导入方法依赖的package包/类
@Test(expectedExceptions = { ConcurrentModificationException.class })
public void testSpliteratorTryAdvance() {
    ServiceLoader<ScriptEngineFactory> sl = load(ScriptEngineFactory.class);
    Stream<Provider<ScriptEngineFactory>> stream = sl.stream();
    Spliterator<Provider<ScriptEngineFactory>> spliterator = stream.spliterator();
    sl.reload();
    spliterator.tryAdvance(System.out::println);
}
 

import java.util.stream.Stream; //导入方法依赖的package包/类
/**
 * Returns a stream in which each element is the result of passing the corresponding element of
 * each of {@code streamA} and {@code streamB} to {@code function}.
 *
 * <p>For example:
 *
 * <pre>{@code
 * Streams.zip(
 *   Stream.of("foo1", "foo2", "foo3"),
 *   Stream.of("bar1", "bar2"),
 *   (arg1, arg2) -> arg1 + ":" + arg2)
 * }</pre>
 *
 * <p>will return {@code Stream.of("foo1:bar1", "foo2:bar2")}.
 *
 * <p>The resulting stream will only be as long as the shorter of the two input streams; if one
 * stream is longer, its extra elements will be ignored.
 *
 * <p>The resulting stream is not <a
 * href="http://gee.cs.oswego.edu/dl/html/StreamParallelGuidance.html">efficiently splittable</a>.
 * This may harm parallel performance.
 */
public static <A, B, R> Stream<R> zip(
    Stream<A> streamA, Stream<B> streamB, BiFunction<? super A, ? super B, R> function) {
  checkNotNull(streamA);
  checkNotNull(streamB);
  checkNotNull(function);
  boolean isParallel = streamA.isParallel() || streamB.isParallel(); // same as Stream.concat
  Spliterator<A> splitrA = streamA.spliterator();
  Spliterator<B> splitrB = streamB.spliterator();
  int characteristics =
      splitrA.characteristics()
          & splitrB.characteristics()
          & (Spliterator.SIZED | Spliterator.ORDERED);
  Iterator<A> itrA = Spliterators.iterator(splitrA);
  Iterator<B> itrB = Spliterators.iterator(splitrB);
  return StreamSupport.stream(
      new AbstractSpliterator<R>(
          Math.min(splitrA.estimateSize(), splitrB.estimateSize()), characteristics) {
        @Override
        public boolean tryAdvance(Consumer<? super R> action) {
          if (itrA.hasNext() && itrB.hasNext()) {
            action.accept(function.apply(itrA.next(), itrB.next()));
            return true;
          }
          return false;
        }
      },
      isParallel);
}
 

import java.util.stream.Stream; //导入方法依赖的package包/类
private BackfillStitchingEventForwardsSpliterator(Stream<ResolvedEvent> backfillStream, Stream<ResolvedEvent> liveStream, StitchedPosition startingPositionExclusive) {
    this.backfillSpliterator = backfillStream.spliterator();
    this.liveSpliterator = liveStream.spliterator();
    this.lastPosition = startingPositionExclusive;
}