319 lines
16 KiB
Java
319 lines
16 KiB
Java
/*
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* Copyright (c) 2012, 2013, Oracle and/or its affiliates. All rights reserved.
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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*
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* This code is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License version 2 only, as
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* published by the Free Software Foundation. Oracle designates this
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* particular file as subject to the "Classpath" exception as provided
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* by Oracle in the LICENSE file that accompanied this code.
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*
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* This code is distributed in the hope that it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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* version 2 for more details (a copy is included in the LICENSE file that
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* accompanied this code).
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*
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* You should have received a copy of the GNU General Public License version
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* 2 along with this work; if not, write to the Free Software Foundation,
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* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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*
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* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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* or visit www.oracle.com if you need additional information or have any
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* questions.
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*/
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package java.util.stream;
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import java.util.Objects;
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import java.util.Spliterator;
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import java.util.function.Supplier;
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/**
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* Low-level utility methods for creating and manipulating streams.
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*
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* <p>This class is mostly for library writers presenting stream views
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* of data structures; most static stream methods intended for end users are in
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* the various {@code Stream} classes.
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*
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* @since 1.8
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*/
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public final class StreamSupport {
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// Suppresses default constructor, ensuring non-instantiability.
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private StreamSupport() {}
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/**
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* Creates a new sequential or parallel {@code Stream} from a
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* {@code Spliterator}.
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*
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* <p>The spliterator is only traversed, split, or queried for estimated
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* size after the terminal operation of the stream pipeline commences.
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*
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* <p>It is strongly recommended the spliterator report a characteristic of
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* {@code IMMUTABLE} or {@code CONCURRENT}, or be
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* <a href="../Spliterator.html#binding">late-binding</a>. Otherwise,
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* {@link #stream(java.util.function.Supplier, int, boolean)} should be used
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* to reduce the scope of potential interference with the source. See
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* <a href="package-summary.html#NonInterference">Non-Interference</a> for
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* more details.
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*
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* @param <T> the type of stream elements
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* @param spliterator a {@code Spliterator} describing the stream elements
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* @param parallel if {@code true} then the returned stream is a parallel
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* stream; if {@code false} the returned stream is a sequential
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* stream.
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* @return a new sequential or parallel {@code Stream}
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*/
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public static <T> Stream<T> stream(Spliterator<T> spliterator, boolean parallel) {
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Objects.requireNonNull(spliterator);
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return new ReferencePipeline.Head<>(spliterator,
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StreamOpFlag.fromCharacteristics(spliterator),
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parallel);
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}
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/**
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* Creates a new sequential or parallel {@code Stream} from a
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* {@code Supplier} of {@code Spliterator}.
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*
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* <p>The {@link Supplier#get()} method will be invoked on the supplier no
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* more than once, and only after the terminal operation of the stream pipeline
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* commences.
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*
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* <p>For spliterators that report a characteristic of {@code IMMUTABLE}
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* or {@code CONCURRENT}, or that are
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* <a href="../Spliterator.html#binding">late-binding</a>, it is likely
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* more efficient to use {@link #stream(java.util.Spliterator, boolean)}
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* instead.
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* <p>The use of a {@code Supplier} in this form provides a level of
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* indirection that reduces the scope of potential interference with the
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* source. Since the supplier is only invoked after the terminal operation
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* commences, any modifications to the source up to the start of the
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* terminal operation are reflected in the stream result. See
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* <a href="package-summary.html#NonInterference">Non-Interference</a> for
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* more details.
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*
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* @param <T> the type of stream elements
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* @param supplier a {@code Supplier} of a {@code Spliterator}
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* @param characteristics Spliterator characteristics of the supplied
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* {@code Spliterator}. The characteristics must be equal to
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* {@code supplier.get().characteristics()}, otherwise undefined
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* behavior may occur when terminal operation commences.
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* @param parallel if {@code true} then the returned stream is a parallel
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* stream; if {@code false} the returned stream is a sequential
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* stream.
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* @return a new sequential or parallel {@code Stream}
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* @see #stream(java.util.Spliterator, boolean)
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*/
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public static <T> Stream<T> stream(Supplier<? extends Spliterator<T>> supplier,
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int characteristics,
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boolean parallel) {
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Objects.requireNonNull(supplier);
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return new ReferencePipeline.Head<>(supplier,
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StreamOpFlag.fromCharacteristics(characteristics),
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parallel);
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}
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/**
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* Creates a new sequential or parallel {@code IntStream} from a
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* {@code Spliterator.OfInt}.
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*
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* <p>The spliterator is only traversed, split, or queried for estimated size
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* after the terminal operation of the stream pipeline commences.
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*
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* <p>It is strongly recommended the spliterator report a characteristic of
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* {@code IMMUTABLE} or {@code CONCURRENT}, or be
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* <a href="../Spliterator.html#binding">late-binding</a>. Otherwise,
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* {@link #intStream(java.util.function.Supplier, int, boolean)} should be
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* used to reduce the scope of potential interference with the source. See
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* <a href="package-summary.html#NonInterference">Non-Interference</a> for
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* more details.
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*
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* @param spliterator a {@code Spliterator.OfInt} describing the stream elements
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* @param parallel if {@code true} then the returned stream is a parallel
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* stream; if {@code false} the returned stream is a sequential
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* stream.
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* @return a new sequential or parallel {@code IntStream}
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*/
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public static IntStream intStream(Spliterator.OfInt spliterator, boolean parallel) {
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return new IntPipeline.Head<>(spliterator,
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StreamOpFlag.fromCharacteristics(spliterator),
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parallel);
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}
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/**
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* Creates a new sequential or parallel {@code IntStream} from a
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* {@code Supplier} of {@code Spliterator.OfInt}.
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*
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* <p>The {@link Supplier#get()} method will be invoked on the supplier no
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* more than once, and only after the terminal operation of the stream pipeline
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* commences.
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*
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* <p>For spliterators that report a characteristic of {@code IMMUTABLE}
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* or {@code CONCURRENT}, or that are
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* <a href="../Spliterator.html#binding">late-binding</a>, it is likely
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* more efficient to use {@link #intStream(java.util.Spliterator.OfInt, boolean)}
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* instead.
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* <p>The use of a {@code Supplier} in this form provides a level of
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* indirection that reduces the scope of potential interference with the
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* source. Since the supplier is only invoked after the terminal operation
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* commences, any modifications to the source up to the start of the
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* terminal operation are reflected in the stream result. See
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* <a href="package-summary.html#NonInterference">Non-Interference</a> for
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* more details.
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*
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* @param supplier a {@code Supplier} of a {@code Spliterator.OfInt}
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* @param characteristics Spliterator characteristics of the supplied
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* {@code Spliterator.OfInt}. The characteristics must be equal to
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* {@code supplier.get().characteristics()}, otherwise undefined
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* behavior may occur when terminal operation commences.
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* @param parallel if {@code true} then the returned stream is a parallel
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* stream; if {@code false} the returned stream is a sequential
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* stream.
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* @return a new sequential or parallel {@code IntStream}
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* @see #intStream(java.util.Spliterator.OfInt, boolean)
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*/
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public static IntStream intStream(Supplier<? extends Spliterator.OfInt> supplier,
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int characteristics,
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boolean parallel) {
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return new IntPipeline.Head<>(supplier,
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StreamOpFlag.fromCharacteristics(characteristics),
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parallel);
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}
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/**
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* Creates a new sequential or parallel {@code LongStream} from a
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* {@code Spliterator.OfLong}.
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*
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* <p>The spliterator is only traversed, split, or queried for estimated
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* size after the terminal operation of the stream pipeline commences.
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*
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* <p>It is strongly recommended the spliterator report a characteristic of
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* {@code IMMUTABLE} or {@code CONCURRENT}, or be
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* <a href="../Spliterator.html#binding">late-binding</a>. Otherwise,
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* {@link #longStream(java.util.function.Supplier, int, boolean)} should be
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* used to reduce the scope of potential interference with the source. See
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* <a href="package-summary.html#NonInterference">Non-Interference</a> for
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* more details.
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*
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* @param spliterator a {@code Spliterator.OfLong} describing the stream elements
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* @param parallel if {@code true} then the returned stream is a parallel
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* stream; if {@code false} the returned stream is a sequential
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* stream.
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* @return a new sequential or parallel {@code LongStream}
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*/
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public static LongStream longStream(Spliterator.OfLong spliterator,
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boolean parallel) {
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return new LongPipeline.Head<>(spliterator,
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StreamOpFlag.fromCharacteristics(spliterator),
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parallel);
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}
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/**
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* Creates a new sequential or parallel {@code LongStream} from a
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* {@code Supplier} of {@code Spliterator.OfLong}.
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*
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* <p>The {@link Supplier#get()} method will be invoked on the supplier no
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* more than once, and only after the terminal operation of the stream pipeline
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* commences.
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*
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* <p>For spliterators that report a characteristic of {@code IMMUTABLE}
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* or {@code CONCURRENT}, or that are
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* <a href="../Spliterator.html#binding">late-binding</a>, it is likely
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* more efficient to use {@link #longStream(java.util.Spliterator.OfLong, boolean)}
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* instead.
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* <p>The use of a {@code Supplier} in this form provides a level of
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* indirection that reduces the scope of potential interference with the
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* source. Since the supplier is only invoked after the terminal operation
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* commences, any modifications to the source up to the start of the
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* terminal operation are reflected in the stream result. See
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* <a href="package-summary.html#NonInterference">Non-Interference</a> for
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* more details.
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*
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* @param supplier a {@code Supplier} of a {@code Spliterator.OfLong}
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* @param characteristics Spliterator characteristics of the supplied
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* {@code Spliterator.OfLong}. The characteristics must be equal to
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* {@code supplier.get().characteristics()}, otherwise undefined
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* behavior may occur when terminal operation commences.
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* @param parallel if {@code true} then the returned stream is a parallel
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* stream; if {@code false} the returned stream is a sequential
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* stream.
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* @return a new sequential or parallel {@code LongStream}
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* @see #longStream(java.util.Spliterator.OfLong, boolean)
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*/
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public static LongStream longStream(Supplier<? extends Spliterator.OfLong> supplier,
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int characteristics,
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boolean parallel) {
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return new LongPipeline.Head<>(supplier,
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StreamOpFlag.fromCharacteristics(characteristics),
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parallel);
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}
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/**
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* Creates a new sequential or parallel {@code DoubleStream} from a
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* {@code Spliterator.OfDouble}.
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*
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* <p>The spliterator is only traversed, split, or queried for estimated size
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* after the terminal operation of the stream pipeline commences.
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*
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* <p>It is strongly recommended the spliterator report a characteristic of
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* {@code IMMUTABLE} or {@code CONCURRENT}, or be
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* <a href="../Spliterator.html#binding">late-binding</a>. Otherwise,
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* {@link #doubleStream(java.util.function.Supplier, int, boolean)} should
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* be used to reduce the scope of potential interference with the source. See
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* <a href="package-summary.html#NonInterference">Non-Interference</a> for
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* more details.
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*
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* @param spliterator A {@code Spliterator.OfDouble} describing the stream elements
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* @param parallel if {@code true} then the returned stream is a parallel
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* stream; if {@code false} the returned stream is a sequential
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* stream.
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* @return a new sequential or parallel {@code DoubleStream}
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*/
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public static DoubleStream doubleStream(Spliterator.OfDouble spliterator,
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boolean parallel) {
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return new DoublePipeline.Head<>(spliterator,
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StreamOpFlag.fromCharacteristics(spliterator),
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parallel);
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}
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/**
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* Creates a new sequential or parallel {@code DoubleStream} from a
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* {@code Supplier} of {@code Spliterator.OfDouble}.
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*
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* <p>The {@link Supplier#get()} method will be invoked on the supplier no
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* more than once, and only after the terminal operation of the stream pipeline
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* commences.
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*
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* <p>For spliterators that report a characteristic of {@code IMMUTABLE}
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* or {@code CONCURRENT}, or that are
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* <a href="../Spliterator.html#binding">late-binding</a>, it is likely
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* more efficient to use {@link #doubleStream(java.util.Spliterator.OfDouble, boolean)}
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* instead.
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* <p>The use of a {@code Supplier} in this form provides a level of
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* indirection that reduces the scope of potential interference with the
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* source. Since the supplier is only invoked after the terminal operation
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* commences, any modifications to the source up to the start of the
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* terminal operation are reflected in the stream result. See
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* <a href="package-summary.html#NonInterference">Non-Interference</a> for
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* more details.
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*
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* @param supplier A {@code Supplier} of a {@code Spliterator.OfDouble}
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* @param characteristics Spliterator characteristics of the supplied
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* {@code Spliterator.OfDouble}. The characteristics must be equal to
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* {@code supplier.get().characteristics()}, otherwise undefined
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* behavior may occur when terminal operation commences.
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* @param parallel if {@code true} then the returned stream is a parallel
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* stream; if {@code false} the returned stream is a sequential
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* stream.
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* @return a new sequential or parallel {@code DoubleStream}
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* @see #doubleStream(java.util.Spliterator.OfDouble, boolean)
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*/
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public static DoubleStream doubleStream(Supplier<? extends Spliterator.OfDouble> supplier,
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int characteristics,
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boolean parallel) {
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return new DoublePipeline.Head<>(supplier,
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StreamOpFlag.fromCharacteristics(characteristics),
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parallel);
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}
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}
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