/*
* Copyright (c) 2012, 2013, Oracle and/or its affiliates. All rights reserved.
* ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
*
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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);
}
}