8012650: Arrays streams methods
8011918: java.util.stream.Streams
Reviewed-by: alanb, mduigou, darcy, henryjen
Contributed-by: brian.goetz@oracle.com, paul.sandoz@oracle.com
/*
* Copyright (c) 2012, 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
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*/
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.
*
* <p>This class is mostly for library writers presenting stream views
* of their data structures; most static stream methods for end users are in
* {@link 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
*/
public class StreamSupport {
/**
* Creates a new sequential {@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(Supplier, int)} should be used to
* reduce the scope of potential interference with the source. See
* <a href="package-summary.html#Non-Interference">Non-Interference</a> for
* more details.
*
* @param <T> the type of stream elements
* @param spliterator a {@code Spliterator} describing the stream elements
* @return a new sequential {@code Stream}
*/
public static <T> Stream<T> stream(Spliterator<T> spliterator) {
Objects.requireNonNull(spliterator);
return new ReferencePipeline.Head<>(spliterator,
StreamOpFlag.fromCharacteristics(spliterator),
false);
}
/**
* Creates a new 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(Supplier, int)} should be used to
* reduce the scope of potential interference with the source. See
* <a href="package-summary.html#Non-Interference">Non-Interference</a> for
* more details.
*
* @param <T> the type of stream elements
* @param spliterator a {@code Spliterator} describing the stream elements
* @return a new parallel {@code Stream}
*/
public static <T> Stream<T> parallelStream(Spliterator<T> spliterator) {
Objects.requireNonNull(spliterator);
return new ReferencePipeline.Head<>(spliterator,
StreamOpFlag.fromCharacteristics(spliterator),
true);
}
/**
* Creates a new sequential {@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 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)} instead.
* 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#Non-Interference">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 source.get().getCharacteristics()}.
* @return a new sequential {@code Stream}
* @see #stream(Spliterator)
*/
public static <T> Stream<T> stream(Supplier<? extends Spliterator<T>> supplier,
int characteristics) {
Objects.requireNonNull(supplier);
return new ReferencePipeline.Head<>(supplier,
StreamOpFlag.fromCharacteristics(characteristics),
false);
}
/**
* Creates a new 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 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(Spliterator)} instead.
* 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#Non-Interference">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 source.get().getCharacteristics()}
* @return a new parallel {@code Stream}
* @see #parallelStream(Spliterator)
*/
public static <T> Stream<T> parallelStream(Supplier<? extends Spliterator<T>> supplier,
int characteristics) {
Objects.requireNonNull(supplier);
return new ReferencePipeline.Head<>(supplier,
StreamOpFlag.fromCharacteristics(characteristics),
true);
}
/**
* Creates a new sequential {@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 #stream(Supplier, int)}} should be used to
* reduce the scope of potential interference with the source. See
* <a href="package-summary.html#Non-Interference">Non-Interference</a> for
* more details.
*
* @param spliterator a {@code Spliterator.OfInt} describing the stream elements
* @return a new sequential {@code IntStream}
*/
public static IntStream intStream(Spliterator.OfInt spliterator) {
return new IntPipeline.Head<>(spliterator,
StreamOpFlag.fromCharacteristics(spliterator),
false);
}
/**
* Creates a new parallel {@code IntStream} from a {@code Spliterator.OfInt}.
*
* <p>he 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(Supplier, int)}} should be used to
* reduce the scope of potential interference with the source. See
* <a href="package-summary.html#Non-Interference">Non-Interference</a> for
* more details.
*
* @param spliterator a {@code Spliterator.OfInt} describing the stream elements
* @return a new parallel {@code IntStream}
*/
public static IntStream intParallelStream(Spliterator.OfInt spliterator) {
return new IntPipeline.Head<>(spliterator,
StreamOpFlag.fromCharacteristics(spliterator),
true);
}
/**
* Creates a new sequential {@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 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(Spliterator.OfInt)} instead.
* 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#Non-Interference">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 source.get().getCharacteristics()}
* @return a new sequential {@code IntStream}
* @see #intStream(Spliterator.OfInt)
*/
public static IntStream intStream(Supplier<? extends Spliterator.OfInt> supplier,
int characteristics) {
return new IntPipeline.Head<>(supplier,
StreamOpFlag.fromCharacteristics(characteristics),
false);
}
/**
* Creates a new 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 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(Spliterator.OfInt)} instead.
* 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#Non-Interference">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 source.get().getCharacteristics()}
* @return a new parallel {@code IntStream}
* @see #intParallelStream(Spliterator.OfInt)
*/
public static IntStream intParallelStream(Supplier<? extends Spliterator.OfInt> supplier,
int characteristics) {
return new IntPipeline.Head<>(supplier,
StreamOpFlag.fromCharacteristics(characteristics),
true);
}
/**
* Creates a new sequential {@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 #stream(Supplier, int)} should be used to
* reduce the scope of potential interference with the source. See
* <a href="package-summary.html#Non-Interference">Non-Interference</a> for
* more details.
*
* @param spliterator a {@code Spliterator.OfLong} describing the stream
* elements
* @return a new sequential {@code LongStream}
*/
public static LongStream longStream(Spliterator.OfLong spliterator) {
return new LongPipeline.Head<>(spliterator,
StreamOpFlag.fromCharacteristics(spliterator),
false);
}
/**
* Creates a new 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 #stream(Supplier, int)} should be used to
* reduce the scope of potential interference with the source. See
* <a href="package-summary.html#Non-Interference">Non-Interference</a> for
* more details.
*
* @param spliterator a {@code Spliterator.OfLong} describing the stream elements
* @return a new parallel {@code LongStream}
*/
public static LongStream longParallelStream(Spliterator.OfLong spliterator) {
return new LongPipeline.Head<>(spliterator,
StreamOpFlag.fromCharacteristics(spliterator),
true);
}
/**
* Creates a new sequential {@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 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(Spliterator.OfLong)} instead.
* 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#Non-Interference">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 source.get().getCharacteristics()}
* @return a new sequential {@code LongStream}
* @see #longStream(Spliterator.OfLong)
*/
public static LongStream longStream(Supplier<? extends Spliterator.OfLong> supplier,
int characteristics) {
return new LongPipeline.Head<>(supplier,
StreamOpFlag.fromCharacteristics(characteristics),
false);
}
/**
* Creates a new 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 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(Spliterator.OfLong)} instead.
* 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#Non-Interference">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 source.get().getCharacteristics()}
* @return A new parallel {@code LongStream}
* @see #longParallelStream(Spliterator.OfLong)
*/
public static LongStream longParallelStream(Supplier<? extends Spliterator.OfLong> supplier,
int characteristics) {
return new LongPipeline.Head<>(supplier,
StreamOpFlag.fromCharacteristics(characteristics),
true);
}
/**
* Creates a new sequential {@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 #stream(Supplier, int)} should be used to
* reduce the scope of potential interference with the source. See
* <a href="package-summary.html#Non-Interference">Non-Interference</a> for
* more details.
*
* @param spliterator A {@code Spliterator.OfDouble} describing the stream elements
* @return A new sequential {@code DoubleStream}
*/
public static DoubleStream doubleStream(Spliterator.OfDouble spliterator) {
return new DoublePipeline.Head<>(spliterator,
StreamOpFlag.fromCharacteristics(spliterator),
false);
}
/**
* Creates a new 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 #stream(Supplier, int)} should be used to
* reduce the scope of potential interference with the source. See
* <a href="package-summary.html#Non-Interference">Non-Interference</a> for
* more details.
*
* @param spliterator A {@code Spliterator.OfDouble} describing the stream elements
* @return A new parallel {@code DoubleStream}
*/
public static DoubleStream doubleParallelStream(Spliterator.OfDouble spliterator) {
return new DoublePipeline.Head<>(spliterator,
StreamOpFlag.fromCharacteristics(spliterator),
true);
}
/**
* Creates a new sequential {@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 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(Spliterator.OfDouble)} instead.
* 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#Non-Interference">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 source.get().getCharacteristics()}
* @return A new sequential {@code DoubleStream}
* @see #doubleStream(Spliterator.OfDouble)
*/
public static DoubleStream doubleStream(Supplier<? extends Spliterator.OfDouble> supplier,
int characteristics) {
return new DoublePipeline.Head<>(supplier,
StreamOpFlag.fromCharacteristics(characteristics),
false);
}
/**
* Creates a new 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 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(Spliterator.OfDouble)} instead.
* 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#Non-Interference">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 source.get().getCharacteristics()}
* @return a new parallel {@code DoubleStream}
* @see #doubleParallelStream(Spliterator.OfDouble)
*/
public static DoubleStream doubleParallelStream(Supplier<? extends Spliterator.OfDouble> supplier,
int characteristics) {
return new DoublePipeline.Head<>(supplier,
StreamOpFlag.fromCharacteristics(characteristics),
true);
}
}