java/10 : java.base/java/util/stream/StreamSupport.java

StreamSupport
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.Objects;
import java.util.Spliterator;
import java.util.function.Supplier;

Low-level utility methods for creating and manipulating streams.
This class is mostly for library writers presenting stream views of data structures; most static stream methods intended for end users are in the various Stream classes. 
Since: 1.8/**
 * Low-level utility methods for creating and manipulating streams.
 *
 * <p>This class is mostly for library writers presenting stream views
 * of data structures; most static stream methods intended for end users are in
 * the various {@code Stream} classes.
 *
 * @since 1.8
 */
public final class StreamSupport {

    // Suppresses default constructor, ensuring non-instantiability.
    private StreamSupport() {}

    Creates a new sequential or parallel Stream from a Spliterator. The spliterator is only traversed, split, or queried for estimated
size after the terminal operation of the stream pipeline commences.
It is strongly recommended the spliterator report a characteristic of IMMUTABLE or CONCURRENT, or be late-binding. Otherwise, stream(Supplier<? extends Spliterator<Object>>, int, boolean) should be used to reduce the scope of potential interference with the source. See Non-Interference for
more details.
Params: spliterator – a Spliterator describing the stream elements
parallel – if true then the returned stream is a parallel stream; if false the returned stream is a sequential stream.
Type parameters: <T> – the type of stream elements
Returns: a new sequential or parallel Stream/**
     * Creates a new sequential or parallel {@code Stream} from a
     * {@code Spliterator}.
     *
     * <p>The spliterator is only traversed, split, or queried for estimated
     * size after the terminal operation of the stream pipeline commences.
     *
     * <p>It is strongly recommended the spliterator report a characteristic of
     * {@code IMMUTABLE} or {@code CONCURRENT}, or be
     * <a href="../Spliterator.html#binding">late-binding</a>.  Otherwise,
     * {@link #stream(java.util.function.Supplier, int, boolean)} should be used
     * to reduce the scope of potential interference with the source.  See
     * <a href="package-summary.html#NonInterference">Non-Interference</a> for
     * more details.
     *
     * @param <T> the type of stream elements
     * @param spliterator a {@code Spliterator} describing the stream elements
     * @param parallel if {@code true} then the returned stream is a parallel
     *        stream; if {@code false} the returned stream is a sequential
     *        stream.
     * @return a new sequential or parallel {@code Stream}
     */
    public static <T> Stream<T> stream(Spliterator<T> spliterator, boolean parallel) {
        Objects.requireNonNull(spliterator);
        return new ReferencePipeline.Head<>(spliterator,
                                            StreamOpFlag.fromCharacteristics(spliterator),
                                            parallel);
    }

    Creates a new sequential or parallel Stream from a Supplier of Spliterator. The Supplier.get() method will be invoked on the supplier no more than once, and only after the terminal operation of the stream pipeline commences. 
For spliterators that report a characteristic of IMMUTABLE or CONCURRENT, or that are late-binding, it is likely more efficient to use stream(Spliterator<Object>, boolean) instead. 
The use of a Supplier in this form provides a level of indirection that reduces the scope of potential interference with the source. Since the supplier is only invoked after the terminal operation commences, any modifications to the source up to the start of the terminal operation are reflected in the stream result. See Non-Interference for
more details.
Params: supplier – a Supplier of a Spliterator
characteristics – Spliterator characteristics of the supplied Spliterator. The characteristics must be equal to supplier.get().characteristics(), otherwise undefined behavior may occur when terminal operation commences.
parallel – if true then the returned stream is a parallel stream; if false the returned stream is a sequential stream.
Type parameters: <T> – the type of stream elements
See Also: stream(Spliterator<Object>, boolean)
Returns: a new sequential or parallel Stream/**
     * Creates a new sequential or parallel {@code Stream} from a
     * {@code Supplier} of {@code Spliterator}.
     *
     * <p>The {@link Supplier#get()} method will be invoked on the supplier no
     * more than once, and only after the terminal operation of the stream pipeline
     * commences.
     *
     * <p>For spliterators that report a characteristic of {@code IMMUTABLE}
     * or {@code CONCURRENT}, or that are
     * <a href="../Spliterator.html#binding">late-binding</a>, it is likely
     * more efficient to use {@link #stream(java.util.Spliterator, boolean)}
     * instead.
     * <p>The use of a {@code Supplier} in this form provides a level of
     * indirection that reduces the scope of potential interference with the
     * source.  Since the supplier is only invoked after the terminal operation
     * commences, any modifications to the source up to the start of the
     * terminal operation are reflected in the stream result.  See
     * <a href="package-summary.html#NonInterference">Non-Interference</a> for
     * more details.
     *
     * @param <T> the type of stream elements
     * @param supplier a {@code Supplier} of a {@code Spliterator}
     * @param characteristics Spliterator characteristics of the supplied
     *        {@code Spliterator}.  The characteristics must be equal to
     *        {@code supplier.get().characteristics()}, otherwise undefined
     *        behavior may occur when terminal operation commences.
     * @param parallel if {@code true} then the returned stream is a parallel
     *        stream; if {@code false} the returned stream is a sequential
     *        stream.
     * @return a new sequential or parallel {@code Stream}
     * @see #stream(java.util.Spliterator, boolean)
     */
    public static <T> Stream<T> stream(Supplier<? extends Spliterator<T>> supplier,
                                       int characteristics,
                                       boolean parallel) {
        Objects.requireNonNull(supplier);
        return new ReferencePipeline.Head<>(supplier,
                                            StreamOpFlag.fromCharacteristics(characteristics),
                                            parallel);
    }

    Creates a new sequential or parallel IntStream from a Spliterator.OfInt. The spliterator is only traversed, split, or queried for estimated size
after the terminal operation of the stream pipeline commences.
It is strongly recommended the spliterator report a characteristic of IMMUTABLE or CONCURRENT, or be late-binding. Otherwise, intStream(Supplier<? extends OfInt>, int, boolean) should be used to reduce the scope of potential interference with the source. See Non-Interference for
more details.
Params: spliterator – a Spliterator.OfInt describing the stream elements
parallel – if true then the returned stream is a parallel stream; if false the returned stream is a sequential stream.
Returns: a new sequential or parallel IntStream/**
     * Creates a new sequential or parallel {@code IntStream} from a
     * {@code Spliterator.OfInt}.
     *
     * <p>The spliterator is only traversed, split, or queried for estimated size
     * after the terminal operation of the stream pipeline commences.
     *
     * <p>It is strongly recommended the spliterator report a characteristic of
     * {@code IMMUTABLE} or {@code CONCURRENT}, or be
     * <a href="../Spliterator.html#binding">late-binding</a>.  Otherwise,
     * {@link #intStream(java.util.function.Supplier, int, boolean)} should be
     * used to reduce the scope of potential interference with the source.  See
     * <a href="package-summary.html#NonInterference">Non-Interference</a> for
     * more details.
     *
     * @param spliterator a {@code Spliterator.OfInt} describing the stream elements
     * @param parallel if {@code true} then the returned stream is a parallel
     *        stream; if {@code false} the returned stream is a sequential
     *        stream.
     * @return a new sequential or parallel {@code IntStream}
     */
    public static IntStream intStream(Spliterator.OfInt spliterator, boolean parallel) {
        return new IntPipeline.Head<>(spliterator,
                                      StreamOpFlag.fromCharacteristics(spliterator),
                                      parallel);
    }

    Creates a new sequential or parallel IntStream from a Supplier of Spliterator.OfInt. The Supplier.get() method will be invoked on the supplier no more than once, and only after the terminal operation of the stream pipeline commences. 
For spliterators that report a characteristic of IMMUTABLE or CONCURRENT, or that are late-binding, it is likely more efficient to use intStream(OfInt, boolean) instead. 
The use of a Supplier in this form provides a level of indirection that reduces the scope of potential interference with the source. Since the supplier is only invoked after the terminal operation commences, any modifications to the source up to the start of the terminal operation are reflected in the stream result. See Non-Interference for
more details.
Params: supplier – a Supplier of a Spliterator.OfInt
characteristics – Spliterator characteristics of the supplied Spliterator.OfInt. The characteristics must be equal to supplier.get().characteristics(), otherwise undefined behavior may occur when terminal operation commences.
parallel – if true then the returned stream is a parallel stream; if false the returned stream is a sequential stream.
See Also: intStream(OfInt, boolean)
Returns: a new sequential or parallel IntStream/**
     * Creates a new sequential or parallel {@code IntStream} from a
     * {@code Supplier} of {@code Spliterator.OfInt}.
     *
     * <p>The {@link Supplier#get()} method will be invoked on the supplier no
     * more than once, and only after the terminal operation of the stream pipeline
     * commences.
     *
     * <p>For spliterators that report a characteristic of {@code IMMUTABLE}
     * or {@code CONCURRENT}, or that are
     * <a href="../Spliterator.html#binding">late-binding</a>, it is likely
     * more efficient to use {@link #intStream(java.util.Spliterator.OfInt, boolean)}
     * instead.
     * <p>The use of a {@code Supplier} in this form provides a level of
     * indirection that reduces the scope of potential interference with the
     * source.  Since the supplier is only invoked after the terminal operation
     * commences, any modifications to the source up to the start of the
     * terminal operation are reflected in the stream result.  See
     * <a href="package-summary.html#NonInterference">Non-Interference</a> for
     * more details.
     *
     * @param supplier a {@code Supplier} of a {@code Spliterator.OfInt}
     * @param characteristics Spliterator characteristics of the supplied
     *        {@code Spliterator.OfInt}.  The characteristics must be equal to
     *        {@code supplier.get().characteristics()}, otherwise undefined
     *        behavior may occur when terminal operation commences.
     * @param parallel if {@code true} then the returned stream is a parallel
     *        stream; if {@code false} the returned stream is a sequential
     *        stream.
     * @return a new sequential or parallel {@code IntStream}
     * @see #intStream(java.util.Spliterator.OfInt, boolean)
     */
    public static IntStream intStream(Supplier<? extends Spliterator.OfInt> supplier,
                                      int characteristics,
                                      boolean parallel) {
        return new IntPipeline.Head<>(supplier,
                                      StreamOpFlag.fromCharacteristics(characteristics),
                                      parallel);
    }

    Creates a new sequential or parallel LongStream from a Spliterator.OfLong. The spliterator is only traversed, split, or queried for estimated
size after the terminal operation of the stream pipeline commences.
It is strongly recommended the spliterator report a characteristic of IMMUTABLE or CONCURRENT, or be late-binding. Otherwise, longStream(Supplier<? extends OfLong>, int, boolean) should be used to reduce the scope of potential interference with the source. See Non-Interference for
more details.
Params: spliterator – a Spliterator.OfLong describing the stream elements
parallel – if true then the returned stream is a parallel stream; if false the returned stream is a sequential stream.
Returns: a new sequential or parallel LongStream/**
     * Creates a new sequential or parallel {@code LongStream} from a
     * {@code Spliterator.OfLong}.
     *
     * <p>The spliterator is only traversed, split, or queried for estimated
     * size after the terminal operation of the stream pipeline commences.
     *
     * <p>It is strongly recommended the spliterator report a characteristic of
     * {@code IMMUTABLE} or {@code CONCURRENT}, or be
     * <a href="../Spliterator.html#binding">late-binding</a>.  Otherwise,
     * {@link #longStream(java.util.function.Supplier, int, boolean)} should be
     * used to reduce the scope of potential interference with the source.  See
     * <a href="package-summary.html#NonInterference">Non-Interference</a> for
     * more details.
     *
     * @param spliterator a {@code Spliterator.OfLong} describing the stream elements
     * @param parallel if {@code true} then the returned stream is a parallel
     *        stream; if {@code false} the returned stream is a sequential
     *        stream.
     * @return a new sequential or parallel {@code LongStream}
     */
    public static LongStream longStream(Spliterator.OfLong spliterator,
                                        boolean parallel) {
        return new LongPipeline.Head<>(spliterator,
                                       StreamOpFlag.fromCharacteristics(spliterator),
                                       parallel);
    }

    Creates a new sequential or parallel LongStream from a Supplier of Spliterator.OfLong. The Supplier.get() method will be invoked on the supplier no more than once, and only after the terminal operation of the stream pipeline commences. 
For spliterators that report a characteristic of IMMUTABLE or CONCURRENT, or that are late-binding, it is likely more efficient to use longStream(OfLong, boolean) instead. 
The use of a Supplier in this form provides a level of indirection that reduces the scope of potential interference with the source. Since the supplier is only invoked after the terminal operation commences, any modifications to the source up to the start of the terminal operation are reflected in the stream result. See Non-Interference for
more details.
Params: supplier – a Supplier of a Spliterator.OfLong
characteristics – Spliterator characteristics of the supplied Spliterator.OfLong. The characteristics must be equal to supplier.get().characteristics(), otherwise undefined behavior may occur when terminal operation commences.
parallel – if true then the returned stream is a parallel stream; if false the returned stream is a sequential stream.
See Also: longStream(OfLong, boolean)
Returns: a new sequential or parallel LongStream/**
     * Creates a new sequential or parallel {@code LongStream} from a
     * {@code Supplier} of {@code Spliterator.OfLong}.
     *
     * <p>The {@link Supplier#get()} method will be invoked on the supplier no
     * more than once, and only after the terminal operation of the stream pipeline
     * commences.
     *
     * <p>For spliterators that report a characteristic of {@code IMMUTABLE}
     * or {@code CONCURRENT}, or that are
     * <a href="../Spliterator.html#binding">late-binding</a>, it is likely
     * more efficient to use {@link #longStream(java.util.Spliterator.OfLong, boolean)}
     * instead.
     * <p>The use of a {@code Supplier} in this form provides a level of
     * indirection that reduces the scope of potential interference with the
     * source.  Since the supplier is only invoked after the terminal operation
     * commences, any modifications to the source up to the start of the
     * terminal operation are reflected in the stream result.  See
     * <a href="package-summary.html#NonInterference">Non-Interference</a> for
     * more details.
     *
     * @param supplier a {@code Supplier} of a {@code Spliterator.OfLong}
     * @param characteristics Spliterator characteristics of the supplied
     *        {@code Spliterator.OfLong}.  The characteristics must be equal to
     *        {@code supplier.get().characteristics()}, otherwise undefined
     *        behavior may occur when terminal operation commences.
     * @param parallel if {@code true} then the returned stream is a parallel
     *        stream; if {@code false} the returned stream is a sequential
     *        stream.
     * @return a new sequential or parallel {@code LongStream}
     * @see #longStream(java.util.Spliterator.OfLong, boolean)
     */
    public static LongStream longStream(Supplier<? extends Spliterator.OfLong> supplier,
                                        int characteristics,
                                        boolean parallel) {
        return new LongPipeline.Head<>(supplier,
                                       StreamOpFlag.fromCharacteristics(characteristics),
                                       parallel);
    }

    Creates a new sequential or parallel DoubleStream from a Spliterator.OfDouble. The spliterator is only traversed, split, or queried for estimated size
after the terminal operation of the stream pipeline commences.
It is strongly recommended the spliterator report a characteristic of IMMUTABLE or CONCURRENT, or be late-binding. Otherwise, doubleStream(Supplier<? extends OfDouble>, int, boolean) should be used to reduce the scope of potential interference with the source. See Non-Interference for
more details.
Params: spliterator – A Spliterator.OfDouble describing the stream elements
parallel – if true then the returned stream is a parallel stream; if false the returned stream is a sequential stream.
Returns: a new sequential or parallel DoubleStream/**
     * Creates a new sequential or parallel {@code DoubleStream} from a
     * {@code Spliterator.OfDouble}.
     *
     * <p>The spliterator is only traversed, split, or queried for estimated size
     * after the terminal operation of the stream pipeline commences.
     *
     * <p>It is strongly recommended the spliterator report a characteristic of
     * {@code IMMUTABLE} or {@code CONCURRENT}, or be
     * <a href="../Spliterator.html#binding">late-binding</a>.  Otherwise,
     * {@link #doubleStream(java.util.function.Supplier, int, boolean)} should
     * be used to reduce the scope of potential interference with the source.  See
     * <a href="package-summary.html#NonInterference">Non-Interference</a> for
     * more details.
     *
     * @param spliterator A {@code Spliterator.OfDouble} describing the stream elements
     * @param parallel if {@code true} then the returned stream is a parallel
     *        stream; if {@code false} the returned stream is a sequential
     *        stream.
     * @return a new sequential or parallel {@code DoubleStream}
     */
    public static DoubleStream doubleStream(Spliterator.OfDouble spliterator,
                                            boolean parallel) {
        return new DoublePipeline.Head<>(spliterator,
                                         StreamOpFlag.fromCharacteristics(spliterator),
                                         parallel);
    }

    Creates a new sequential or parallel DoubleStream from a Supplier of Spliterator.OfDouble. The Supplier.get() method will be invoked on the supplier no more than once, and only after the terminal operation of the stream pipeline commences. 
For spliterators that report a characteristic of IMMUTABLE or CONCURRENT, or that are late-binding, it is likely more efficient to use doubleStream(OfDouble, boolean) instead. 
The use of a Supplier in this form provides a level of indirection that reduces the scope of potential interference with the source. Since the supplier is only invoked after the terminal operation commences, any modifications to the source up to the start of the terminal operation are reflected in the stream result. See Non-Interference for
more details.
Params: supplier – A Supplier of a Spliterator.OfDouble
characteristics – Spliterator characteristics of the supplied Spliterator.OfDouble. The characteristics must be equal to supplier.get().characteristics(), otherwise undefined behavior may occur when terminal operation commences.
parallel – if true then the returned stream is a parallel stream; if false the returned stream is a sequential stream.
See Also: doubleStream(OfDouble, boolean)
Returns: a new sequential or parallel DoubleStream/**
     * Creates a new sequential or parallel {@code DoubleStream} from a
     * {@code Supplier} of {@code Spliterator.OfDouble}.
     *
     * <p>The {@link Supplier#get()} method will be invoked on the supplier no
     * more than once, and only after the terminal operation of the stream pipeline
     * commences.
     *
     * <p>For spliterators that report a characteristic of {@code IMMUTABLE}
     * or {@code CONCURRENT}, or that are
     * <a href="../Spliterator.html#binding">late-binding</a>, it is likely
     * more efficient to use {@link #doubleStream(java.util.Spliterator.OfDouble, boolean)}
     * instead.
     * <p>The use of a {@code Supplier} in this form provides a level of
     * indirection that reduces the scope of potential interference with the
     * source.  Since the supplier is only invoked after the terminal operation
     * commences, any modifications to the source up to the start of the
     * terminal operation are reflected in the stream result.  See
     * <a href="package-summary.html#NonInterference">Non-Interference</a> for
     * more details.
     *
     * @param supplier A {@code Supplier} of a {@code Spliterator.OfDouble}
     * @param characteristics Spliterator characteristics of the supplied
     *        {@code Spliterator.OfDouble}.  The characteristics must be equal to
     *        {@code supplier.get().characteristics()}, otherwise undefined
     *        behavior may occur when terminal operation commences.
     * @param parallel if {@code true} then the returned stream is a parallel
     *        stream; if {@code false} the returned stream is a sequential
     *        stream.
     * @return a new sequential or parallel {@code DoubleStream}
     * @see #doubleStream(java.util.Spliterator.OfDouble, boolean)
     */
    public static DoubleStream doubleStream(Supplier<? extends Spliterator.OfDouble> supplier,
                                            int characteristics,
                                            boolean parallel) {
        return new DoublePipeline.Head<>(supplier,
                                         StreamOpFlag.fromCharacteristics(characteristics),
                                         parallel);
    }
}
Params:	spliterator – a `Spliterator` describing the stream elements parallel – if `true` then the returned stream is a parallel stream; if `false` the returned stream is a sequential stream.
Type parameters:	<T> – the type of stream elements
Returns:	a new sequential or parallel `Stream`
Params:	supplier – a `Supplier` of a `Spliterator` characteristics – Spliterator characteristics of the supplied `Spliterator`. The characteristics must be equal to `supplier.get().characteristics()`, otherwise undefined behavior may occur when terminal operation commences. parallel – if `true` then the returned stream is a parallel stream; if `false` the returned stream is a sequential stream.
Type parameters:	<T> – the type of stream elements
See Also:	stream(Spliterator<Object>, boolean)
Returns:	a new sequential or parallel `Stream`
Params:	spliterator – a `Spliterator.OfInt` describing the stream elements parallel – if `true` then the returned stream is a parallel stream; if `false` the returned stream is a sequential stream.
Returns:	a new sequential or parallel `IntStream`
Params:	spliterator – a `Spliterator.OfLong` describing the stream elements parallel – if `true` then the returned stream is a parallel stream; if `false` the returned stream is a sequential stream.
Returns:	a new sequential or parallel `LongStream`
Params:	spliterator – A `Spliterator.OfDouble` describing the stream elements parallel – if `true` then the returned stream is a parallel stream; if `false` the returned stream is a sequential stream.
Returns:	a new sequential or parallel `DoubleStream`
/

java/ 10/ java.base/java/util/stream/StreamSupport.java
