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* 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.
*
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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 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 {@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 {@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 {@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 {@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 {@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 {@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 {@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 {@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);
}
}