java/11 : java.base/java/util/stream/Streams.java

Streams
https://openjdk.java.net/
GPLv2 + Classpath Exception
/*
 * Copyright (c) 2012, 2013, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.  Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Oracle in the LICENSE file that accompanied this code.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 */
package java.util.stream;

import java.util.Comparator;
import java.util.Objects;
import java.util.Spliterator;
import java.util.function.Consumer;
import java.util.function.DoubleConsumer;
import java.util.function.IntConsumer;
import java.util.function.LongConsumer;
import jdk.internal.HotSpotIntrinsicCandidate;

Utility methods for operating on and creating streams.
Unless otherwise stated, streams are created as sequential streams. A sequential stream can be transformed into a parallel stream by calling the parallel() method on the created stream. 
Since: 1.8/**
 * Utility methods for operating on and creating streams.
 *
 * <p>Unless otherwise stated, streams are created as sequential streams.  A
 * sequential stream can be transformed into a parallel stream by calling the
 * {@code parallel()} method on the created stream.
 *
 * @since 1.8
 */
final class Streams {

    private Streams() {
        throw new Error("no instances");
    }

    An int range spliterator. /**
     * An {@code int} range spliterator.
     */
    static final class RangeIntSpliterator implements Spliterator.OfInt {
        // Can never be greater that upTo, this avoids overflow if upper bound
        // is Integer.MAX_VALUE
        // All elements are traversed if from == upTo & last == 0
        private int from;
        private final int upTo;
        // 1 if the range is closed and the last element has not been traversed
        // Otherwise, 0 if the range is open, or is a closed range and all
        // elements have been traversed
        private int last;

        RangeIntSpliterator(int from, int upTo, boolean closed) {
            this(from, upTo, closed ? 1 : 0);
        }

        private RangeIntSpliterator(int from, int upTo, int last) {
            this.from = from;
            this.upTo = upTo;
            this.last = last;
        }

        @Override
        public boolean tryAdvance(IntConsumer consumer) {
            Objects.requireNonNull(consumer);

            final int i = from;
            if (i < upTo) {
                from++;
                consumer.accept(i);
                return true;
            }
            else if (last > 0) {
                last = 0;
                consumer.accept(i);
                return true;
            }
            return false;
        }

        @Override
        @HotSpotIntrinsicCandidate
        public void forEachRemaining(IntConsumer consumer) {
            Objects.requireNonNull(consumer);

            int i = from;
            final int hUpTo = upTo;
            int hLast = last;
            from = upTo;
            last = 0;
            while (i < hUpTo) {
                consumer.accept(i++);
            }
            if (hLast > 0) {
                // Last element of closed range
                consumer.accept(i);
            }
        }

        @Override
        public long estimateSize() {
            // Ensure ranges of size > Integer.MAX_VALUE report the correct size
            return ((long) upTo) - from + last;
        }

        @Override
        public int characteristics() {
            return Spliterator.ORDERED | Spliterator.SIZED | Spliterator.SUBSIZED |
                   Spliterator.IMMUTABLE | Spliterator.NONNULL |
                   Spliterator.DISTINCT | Spliterator.SORTED;
        }

        @Override
        public Comparator<? super Integer> getComparator() {
            return null;
        }

        @Override
        public Spliterator.OfInt trySplit() {
            long size = estimateSize();
            return size <= 1
                   ? null
                   // Left split always has a half-open range
                   : new RangeIntSpliterator(from, from = from + splitPoint(size), 0);
        }

        The spliterator size below which the spliterator will be split
at the mid-point to produce balanced splits. Above this size the
spliterator will be split at a ratio of
1:(RIGHT_BALANCED_SPLIT_RATIO - 1)
to produce right-balanced splits.
Such splitting ensures that for very large ranges that the left
side of the range will more likely be processed at a lower-depth
than a balanced tree at the expense of a higher-depth for the right
side of the range.
This is optimized for cases such as IntStream.range(0, Integer.MAX_VALUE)
that is likely to be augmented with a limit operation that limits the
number of elements to a count lower than this threshold.
/**
         * The spliterator size below which the spliterator will be split
         * at the mid-point to produce balanced splits. Above this size the
         * spliterator will be split at a ratio of
         * 1:(RIGHT_BALANCED_SPLIT_RATIO - 1)
         * to produce right-balanced splits.
         *
         * <p>Such splitting ensures that for very large ranges that the left
         * side of the range will more likely be processed at a lower-depth
         * than a balanced tree at the expense of a higher-depth for the right
         * side of the range.
         *
         * <p>This is optimized for cases such as IntStream.range(0, Integer.MAX_VALUE)
         * that is likely to be augmented with a limit operation that limits the
         * number of elements to a count lower than this threshold.
         */
        private static final int BALANCED_SPLIT_THRESHOLD = 1 << 24;

        The split ratio of the left and right split when the spliterator
size is above BALANCED_SPLIT_THRESHOLD.
/**
         * The split ratio of the left and right split when the spliterator
         * size is above BALANCED_SPLIT_THRESHOLD.
         */
        private static final int RIGHT_BALANCED_SPLIT_RATIO = 1 << 3;

        private int splitPoint(long size) {
            int d = (size < BALANCED_SPLIT_THRESHOLD) ? 2 : RIGHT_BALANCED_SPLIT_RATIO;
            // Cast to int is safe since:
            //   2 <= size < 2^32
            //   2 <= d <= 8
            return (int) (size / d);
        }
    }

    A long range spliterator. This implementation cannot be used for ranges whose size is greater than Long.MAX_VALUE /**
     * A {@code long} range spliterator.
     *
     * This implementation cannot be used for ranges whose size is greater
     * than Long.MAX_VALUE
     */
    static final class RangeLongSpliterator implements Spliterator.OfLong {
        // Can never be greater that upTo, this avoids overflow if upper bound
        // is Long.MAX_VALUE
        // All elements are traversed if from == upTo & last == 0
        private long from;
        private final long upTo;
        // 1 if the range is closed and the last element has not been traversed
        // Otherwise, 0 if the range is open, or is a closed range and all
        // elements have been traversed
        private int last;

        RangeLongSpliterator(long from, long upTo, boolean closed) {
            this(from, upTo, closed ? 1 : 0);
        }

        private RangeLongSpliterator(long from, long upTo, int last) {
            assert upTo - from + last > 0;
            this.from = from;
            this.upTo = upTo;
            this.last = last;
        }

        @Override
        public boolean tryAdvance(LongConsumer consumer) {
            Objects.requireNonNull(consumer);

            final long i = from;
            if (i < upTo) {
                from++;
                consumer.accept(i);
                return true;
            }
            else if (last > 0) {
                last = 0;
                consumer.accept(i);
                return true;
            }
            return false;
        }

        @Override
        public void forEachRemaining(LongConsumer consumer) {
            Objects.requireNonNull(consumer);

            long i = from;
            final long hUpTo = upTo;
            int hLast = last;
            from = upTo;
            last = 0;
            while (i < hUpTo) {
                consumer.accept(i++);
            }
            if (hLast > 0) {
                // Last element of closed range
                consumer.accept(i);
            }
        }

        @Override
        public long estimateSize() {
            return upTo - from + last;
        }

        @Override
        public int characteristics() {
            return Spliterator.ORDERED | Spliterator.SIZED | Spliterator.SUBSIZED |
                   Spliterator.IMMUTABLE | Spliterator.NONNULL |
                   Spliterator.DISTINCT | Spliterator.SORTED;
        }

        @Override
        public Comparator<? super Long> getComparator() {
            return null;
        }

        @Override
        public Spliterator.OfLong trySplit() {
            long size = estimateSize();
            return size <= 1
                   ? null
                   // Left split always has a half-open range
                   : new RangeLongSpliterator(from, from = from + splitPoint(size), 0);
        }

        The spliterator size below which the spliterator will be split
at the mid-point to produce balanced splits. Above this size the
spliterator will be split at a ratio of
1:(RIGHT_BALANCED_SPLIT_RATIO - 1)
to produce right-balanced splits.
Such splitting ensures that for very large ranges that the left
side of the range will more likely be processed at a lower-depth
than a balanced tree at the expense of a higher-depth for the right
side of the range.
This is optimized for cases such as LongStream.range(0, Long.MAX_VALUE)
that is likely to be augmented with a limit operation that limits the
number of elements to a count lower than this threshold.
/**
         * The spliterator size below which the spliterator will be split
         * at the mid-point to produce balanced splits. Above this size the
         * spliterator will be split at a ratio of
         * 1:(RIGHT_BALANCED_SPLIT_RATIO - 1)
         * to produce right-balanced splits.
         *
         * <p>Such splitting ensures that for very large ranges that the left
         * side of the range will more likely be processed at a lower-depth
         * than a balanced tree at the expense of a higher-depth for the right
         * side of the range.
         *
         * <p>This is optimized for cases such as LongStream.range(0, Long.MAX_VALUE)
         * that is likely to be augmented with a limit operation that limits the
         * number of elements to a count lower than this threshold.
         */
        private static final long BALANCED_SPLIT_THRESHOLD = 1 << 24;

        The split ratio of the left and right split when the spliterator
size is above BALANCED_SPLIT_THRESHOLD.
/**
         * The split ratio of the left and right split when the spliterator
         * size is above BALANCED_SPLIT_THRESHOLD.
         */
        private static final long RIGHT_BALANCED_SPLIT_RATIO = 1 << 3;

        private long splitPoint(long size) {
            long d = (size < BALANCED_SPLIT_THRESHOLD) ? 2 : RIGHT_BALANCED_SPLIT_RATIO;
            // 2 <= size <= Long.MAX_VALUE
            return size / d;
        }
    }

    private abstract static class AbstractStreamBuilderImpl<T, S extends Spliterator<T>> implements Spliterator<T> {
        // >= 0 when building, < 0 when built
        // -1 == no elements
        // -2 == one element, held by first
        // -3 == two or more elements, held by buffer
        int count;

        // Spliterator implementation for 0 or 1 element
        // count == -1 for no elements
        // count == -2 for one element held by first

        @Override
        public S trySplit() {
            return null;
        }

        @Override
        public long estimateSize() {
            return -count - 1;
        }

        @Override
        public int characteristics() {
            return Spliterator.SIZED | Spliterator.SUBSIZED |
                   Spliterator.ORDERED | Spliterator.IMMUTABLE;
        }
    }

    static final class StreamBuilderImpl<T>
            extends AbstractStreamBuilderImpl<T, Spliterator<T>>
            implements Stream.Builder<T> {
        // The first element in the stream
        // valid if count == 1
        T first;

        // The first and subsequent elements in the stream
        // non-null if count == 2
        SpinedBuffer<T> buffer;

        Constructor for building a stream of 0 or more elements.
/**
         * Constructor for building a stream of 0 or more elements.
         */
        StreamBuilderImpl() { }

        Constructor for a singleton stream.
Params: t – the single element/**
         * Constructor for a singleton stream.
         *
         * @param t the single element
         */
        StreamBuilderImpl(T t) {
            first = t;
            count = -2;
        }

        // StreamBuilder implementation

        @Override
        public void accept(T t) {
            if (count == 0) {
                first = t;
                count++;
            }
            else if (count > 0) {
                if (buffer == null) {
                    buffer = new SpinedBuffer<>();
                    buffer.accept(first);
                    count++;
                }

                buffer.accept(t);
            }
            else {
                throw new IllegalStateException();
            }
        }

        public Stream.Builder<T> add(T t) {
            accept(t);
            return this;
        }

        @Override
        public Stream<T> build() {
            int c = count;
            if (c >= 0) {
                // Switch count to negative value signalling the builder is built
                count = -count - 1;
                // Use this spliterator if 0 or 1 elements, otherwise use
                // the spliterator of the spined buffer
                return (c < 2) ? StreamSupport.stream(this, false) : StreamSupport.stream(buffer.spliterator(), false);
            }

            throw new IllegalStateException();
        }

        // Spliterator implementation for 0 or 1 element
        // count == -1 for no elements
        // count == -2 for one element held by first

        @Override
        public boolean tryAdvance(Consumer<? super T> action) {
            Objects.requireNonNull(action);

            if (count == -2) {
                action.accept(first);
                count = -1;
                return true;
            }
            else {
                return false;
            }
        }

        @Override
        public void forEachRemaining(Consumer<? super T> action) {
            Objects.requireNonNull(action);

            if (count == -2) {
                action.accept(first);
                count = -1;
            }
        }
    }

    static final class IntStreamBuilderImpl
            extends AbstractStreamBuilderImpl<Integer, Spliterator.OfInt>
            implements IntStream.Builder, Spliterator.OfInt {
        // The first element in the stream
        // valid if count == 1
        int first;

        // The first and subsequent elements in the stream
        // non-null if count == 2
        SpinedBuffer.OfInt buffer;

        Constructor for building a stream of 0 or more elements.
/**
         * Constructor for building a stream of 0 or more elements.
         */
        IntStreamBuilderImpl() { }

        Constructor for a singleton stream.
Params: t – the single element/**
         * Constructor for a singleton stream.
         *
         * @param t the single element
         */
        IntStreamBuilderImpl(int t) {
            first = t;
            count = -2;
        }

        // StreamBuilder implementation

        @Override
        public void accept(int t) {
            if (count == 0) {
                first = t;
                count++;
            }
            else if (count > 0) {
                if (buffer == null) {
                    buffer = new SpinedBuffer.OfInt();
                    buffer.accept(first);
                    count++;
                }

                buffer.accept(t);
            }
            else {
                throw new IllegalStateException();
            }
        }

        @Override
        public IntStream build() {
            int c = count;
            if (c >= 0) {
                // Switch count to negative value signalling the builder is built
                count = -count - 1;
                // Use this spliterator if 0 or 1 elements, otherwise use
                // the spliterator of the spined buffer
                return (c < 2) ? StreamSupport.intStream(this, false) : StreamSupport.intStream(buffer.spliterator(), false);
            }

            throw new IllegalStateException();
        }

        // Spliterator implementation for 0 or 1 element
        // count == -1 for no elements
        // count == -2 for one element held by first

        @Override
        public boolean tryAdvance(IntConsumer action) {
            Objects.requireNonNull(action);

            if (count == -2) {
                action.accept(first);
                count = -1;
                return true;
            }
            else {
                return false;
            }
        }

        @Override
        public void forEachRemaining(IntConsumer action) {
            Objects.requireNonNull(action);

            if (count == -2) {
                action.accept(first);
                count = -1;
            }
        }
    }

    static final class LongStreamBuilderImpl
            extends AbstractStreamBuilderImpl<Long, Spliterator.OfLong>
            implements LongStream.Builder, Spliterator.OfLong {
        // The first element in the stream
        // valid if count == 1
        long first;

        // The first and subsequent elements in the stream
        // non-null if count == 2
        SpinedBuffer.OfLong buffer;

        Constructor for building a stream of 0 or more elements.
/**
         * Constructor for building a stream of 0 or more elements.
         */
        LongStreamBuilderImpl() { }

        Constructor for a singleton stream.
Params: t – the single element/**
         * Constructor for a singleton stream.
         *
         * @param t the single element
         */
        LongStreamBuilderImpl(long t) {
            first = t;
            count = -2;
        }

        // StreamBuilder implementation

        @Override
        public void accept(long t) {
            if (count == 0) {
                first = t;
                count++;
            }
            else if (count > 0) {
                if (buffer == null) {
                    buffer = new SpinedBuffer.OfLong();
                    buffer.accept(first);
                    count++;
                }

                buffer.accept(t);
            }
            else {
                throw new IllegalStateException();
            }
        }

        @Override
        public LongStream build() {
            int c = count;
            if (c >= 0) {
                // Switch count to negative value signalling the builder is built
                count = -count - 1;
                // Use this spliterator if 0 or 1 elements, otherwise use
                // the spliterator of the spined buffer
                return (c < 2) ? StreamSupport.longStream(this, false) : StreamSupport.longStream(buffer.spliterator(), false);
            }

            throw new IllegalStateException();
        }

        // Spliterator implementation for 0 or 1 element
        // count == -1 for no elements
        // count == -2 for one element held by first

        @Override
        public boolean tryAdvance(LongConsumer action) {
            Objects.requireNonNull(action);

            if (count == -2) {
                action.accept(first);
                count = -1;
                return true;
            }
            else {
                return false;
            }
        }

        @Override
        public void forEachRemaining(LongConsumer action) {
            Objects.requireNonNull(action);

            if (count == -2) {
                action.accept(first);
                count = -1;
            }
        }
    }

    static final class DoubleStreamBuilderImpl
            extends AbstractStreamBuilderImpl<Double, Spliterator.OfDouble>
            implements DoubleStream.Builder, Spliterator.OfDouble {
        // The first element in the stream
        // valid if count == 1
        double first;

        // The first and subsequent elements in the stream
        // non-null if count == 2
        SpinedBuffer.OfDouble buffer;

        Constructor for building a stream of 0 or more elements.
/**
         * Constructor for building a stream of 0 or more elements.
         */
        DoubleStreamBuilderImpl() { }

        Constructor for a singleton stream.
Params: t – the single element/**
         * Constructor for a singleton stream.
         *
         * @param t the single element
         */
        DoubleStreamBuilderImpl(double t) {
            first = t;
            count = -2;
        }

        // StreamBuilder implementation

        @Override
        public void accept(double t) {
            if (count == 0) {
                first = t;
                count++;
            }
            else if (count > 0) {
                if (buffer == null) {
                    buffer = new SpinedBuffer.OfDouble();
                    buffer.accept(first);
                    count++;
                }

                buffer.accept(t);
            }
            else {
                throw new IllegalStateException();
            }
        }

        @Override
        public DoubleStream build() {
            int c = count;
            if (c >= 0) {
                // Switch count to negative value signalling the builder is built
                count = -count - 1;
                // Use this spliterator if 0 or 1 elements, otherwise use
                // the spliterator of the spined buffer
                return (c < 2) ? StreamSupport.doubleStream(this, false) : StreamSupport.doubleStream(buffer.spliterator(), false);
            }

            throw new IllegalStateException();
        }

        // Spliterator implementation for 0 or 1 element
        // count == -1 for no elements
        // count == -2 for one element held by first

        @Override
        public boolean tryAdvance(DoubleConsumer action) {
            Objects.requireNonNull(action);

            if (count == -2) {
                action.accept(first);
                count = -1;
                return true;
            }
            else {
                return false;
            }
        }

        @Override
        public void forEachRemaining(DoubleConsumer action) {
            Objects.requireNonNull(action);

            if (count == -2) {
                action.accept(first);
                count = -1;
            }
        }
    }

    abstract static class ConcatSpliterator<T, T_SPLITR extends Spliterator<T>>
            implements Spliterator<T> {
        protected final T_SPLITR aSpliterator;
        protected final T_SPLITR bSpliterator;
        // True when no split has occurred, otherwise false
        boolean beforeSplit;
        // Never read after splitting
        final boolean unsized;

        public ConcatSpliterator(T_SPLITR aSpliterator, T_SPLITR bSpliterator) {
            this.aSpliterator = aSpliterator;
            this.bSpliterator = bSpliterator;
            beforeSplit = true;
            // The spliterator is known to be unsized before splitting if the
            // sum of the estimates overflows.
            unsized = aSpliterator.estimateSize() + bSpliterator.estimateSize() < 0;
        }

        @Override
        public T_SPLITR trySplit() {
            @SuppressWarnings("unchecked")
            T_SPLITR ret = beforeSplit ? aSpliterator : (T_SPLITR) bSpliterator.trySplit();
            beforeSplit = false;
            return ret;
        }

        @Override
        public boolean tryAdvance(Consumer<? super T> consumer) {
            boolean hasNext;
            if (beforeSplit) {
                hasNext = aSpliterator.tryAdvance(consumer);
                if (!hasNext) {
                    beforeSplit = false;
                    hasNext = bSpliterator.tryAdvance(consumer);
                }
            }
            else
                hasNext = bSpliterator.tryAdvance(consumer);
            return hasNext;
        }

        @Override
        public void forEachRemaining(Consumer<? super T> consumer) {
            if (beforeSplit)
                aSpliterator.forEachRemaining(consumer);
            bSpliterator.forEachRemaining(consumer);
        }

        @Override
        public long estimateSize() {
            if (beforeSplit) {
                // If one or both estimates are Long.MAX_VALUE then the sum
                // will either be Long.MAX_VALUE or overflow to a negative value
                long size = aSpliterator.estimateSize() + bSpliterator.estimateSize();
                return (size >= 0) ? size : Long.MAX_VALUE;
            }
            else {
                return bSpliterator.estimateSize();
            }
        }

        @Override
        public int characteristics() {
            if (beforeSplit) {
                // Concatenation loses DISTINCT and SORTED characteristics
                return aSpliterator.characteristics() & bSpliterator.characteristics()
                       & ~(Spliterator.DISTINCT | Spliterator.SORTED
                           | (unsized ? Spliterator.SIZED | Spliterator.SUBSIZED : 0));
            }
            else {
                return bSpliterator.characteristics();
            }
        }

        @Override
        public Comparator<? super T> getComparator() {
            if (beforeSplit)
                throw new IllegalStateException();
            return bSpliterator.getComparator();
        }

        static class OfRef<T> extends ConcatSpliterator<T, Spliterator<T>> {
            OfRef(Spliterator<T> aSpliterator, Spliterator<T> bSpliterator) {
                super(aSpliterator, bSpliterator);
            }
        }

        private abstract static class OfPrimitive<T, T_CONS, T_SPLITR extends Spliterator.OfPrimitive<T, T_CONS, T_SPLITR>>
                extends ConcatSpliterator<T, T_SPLITR>
                implements Spliterator.OfPrimitive<T, T_CONS, T_SPLITR> {
            private OfPrimitive(T_SPLITR aSpliterator, T_SPLITR bSpliterator) {
                super(aSpliterator, bSpliterator);
            }

            @Override
            public boolean tryAdvance(T_CONS action) {
                boolean hasNext;
                if (beforeSplit) {
                    hasNext = aSpliterator.tryAdvance(action);
                    if (!hasNext) {
                        beforeSplit = false;
                        hasNext = bSpliterator.tryAdvance(action);
                    }
                }
                else
                    hasNext = bSpliterator.tryAdvance(action);
                return hasNext;
            }

            @Override
            public void forEachRemaining(T_CONS action) {
                if (beforeSplit)
                    aSpliterator.forEachRemaining(action);
                bSpliterator.forEachRemaining(action);
            }
        }

        static class OfInt
                extends ConcatSpliterator.OfPrimitive<Integer, IntConsumer, Spliterator.OfInt>
                implements Spliterator.OfInt {
            OfInt(Spliterator.OfInt aSpliterator, Spliterator.OfInt bSpliterator) {
                super(aSpliterator, bSpliterator);
            }
        }

        static class OfLong
                extends ConcatSpliterator.OfPrimitive<Long, LongConsumer, Spliterator.OfLong>
                implements Spliterator.OfLong {
            OfLong(Spliterator.OfLong aSpliterator, Spliterator.OfLong bSpliterator) {
                super(aSpliterator, bSpliterator);
            }
        }

        static class OfDouble
                extends ConcatSpliterator.OfPrimitive<Double, DoubleConsumer, Spliterator.OfDouble>
                implements Spliterator.OfDouble {
            OfDouble(Spliterator.OfDouble aSpliterator, Spliterator.OfDouble bSpliterator) {
                super(aSpliterator, bSpliterator);
            }
        }
    }

    Given two Runnables, return a Runnable that executes both in sequence,
even if the first throws an exception, and if both throw exceptions, add
any exceptions thrown by the second as suppressed exceptions of the first.
/**
     * Given two Runnables, return a Runnable that executes both in sequence,
     * even if the first throws an exception, and if both throw exceptions, add
     * any exceptions thrown by the second as suppressed exceptions of the first.
     */
    static Runnable composeWithExceptions(Runnable a, Runnable b) {
        return new Runnable() {
            @Override
            public void run() {
                try {
                    a.run();
                }
                catch (Throwable e1) {
                    try {
                        b.run();
                    }
                    catch (Throwable e2) {
                        try {
                            e1.addSuppressed(e2);
                        } catch (Throwable ignore) {}
                    }
                    throw e1;
                }
                b.run();
            }
        };
    }

    Given two streams, return a Runnable that executes both of their BaseStream.close methods in sequence, even if the first throws an exception, and if both throw exceptions, add any exceptions thrown by the second as suppressed exceptions of the first. /**
     * Given two streams, return a Runnable that
     * executes both of their {@link BaseStream#close} methods in sequence,
     * even if the first throws an exception, and if both throw exceptions, add
     * any exceptions thrown by the second as suppressed exceptions of the first.
     */
    static Runnable composedClose(BaseStream<?, ?> a, BaseStream<?, ?> b) {
        return new Runnable() {
            @Override
            public void run() {
                try {
                    a.close();
                }
                catch (Throwable e1) {
                    try {
                        b.close();
                    }
                    catch (Throwable e2) {
                        try {
                            e1.addSuppressed(e2);
                        } catch (Throwable ignore) {}
                    }
                    throw e1;
                }
                b.close();
            }
        };
    }
}
/

java/ 11/ java.base/java/util/stream/Streams.java
