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/*
* Copyright (c) 2012, 2015, 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 java8.util.stream;
import java.util.Collection;
import java8.util.Objects;
import java8.util.Spliterators;
import java8.util.function.Supplier;
import java8.util.Spliterator;
/**
* 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 {@code Streams} classes.
*
* @since 1.8
*/
public final class StreamSupport {
// Suppresses default constructor, ensuring non-instantiability.
private StreamSupport() {}
/**
* Creates a new sequential {@code Stream} using either the given
* collection's {@link java.util.Collection#iterator()} as the source of
* elements for an internally created {@code Spliterator} which will report
* the collection's {@link java.util.Collection#size()} as its initial size
* or a specialized {@code Spliterator} implementation (effectively the same
* one that Java 8 uses) if the passed {@code Collection} is one of the
* types listed below.
*
*
* - java.util.ArrayList
* - java.util.Arrays.ArrayList
* - java.util.ArrayDeque
* - java.util.Vector
* - java.util.LinkedList
* - java.util.HashSet
* - java.util.LinkedHashSet
* - java.util.PriorityQueue
* - java.util.concurrent.ArrayBlockingQueue
* - java.util.concurrent.LinkedBlockingQueue
* - java.util.concurrent.LinkedBlockingDeque
* - java.util.concurrent.PriorityBlockingQueue
* - java.util.concurrent.CopyOnWriteArrayList
* - java.util.concurrent.CopyOnWriteArraySet
* - The collections returned from the java.util.HashMap methods
* #keySet(), #entrySet() and #values()
*
*
*
* Otherwise, if the given collection is a {@link java.util.List}, the
* implementation creates a
* late-binding
* spliterator as follows:
*
* - If the list is an instance of {@link java.util.RandomAccess} then
* the default implementation creates a spliterator that traverses
* elements by invoking the method {@link java.util.List#get}. If
* such invocation results or would result in an
* {@code IndexOutOfBoundsException} then the spliterator will
* fail-fast and throw a {@code ConcurrentModificationException}.
* If the list is also an instance of {@link java.util.AbstractList}
* then the spliterator will use the list's
* {@link java.util.AbstractList#modCount modCount} field to provide
* additional fail-fast behavior.
*
- Otherwise, the default implementation creates a spliterator from
* the list's {@code Iterator}. The spliterator inherits the
* fail-fast properties of the list's iterator.
*
*
*
* The {@code Spliterator}s for {@code CopyOnWriteArrayList} and
* {@code CopyOnWriteArraySet} provide a snapshot of the state of the
* collection when the {@code Stream} was created, otherwise the created
* spliterator is
* late-binding, inherits
* the fail-fast properties of the collection's iterator, and
* implements {@code trySplit} to permit limited parallelism.
*
*
* The created spliterator is only traversed, split, or queried for
* estimated size after the terminal operation of the stream pipeline
* commences.
*
* @param
* Type of elements
* @param c
* The collection
* @return a new sequential {@code Stream}
* @throws NullPointerException
* if the given collection is {@code null}
*/
public static Stream stream(Collection c) {
return stream(Spliterators.spliterator(c), false);
}
/**
* Creates a new possibly parallel {@code Stream} using either the given
* collection's {@link java.util.Collection#iterator()} as the source of
* elements for an internally created {@code Spliterator} which will report
* the collection's {@link java.util.Collection#size()} as its initial size
* or a specialized {@code Spliterator} implementation (effectively the same
* one that Java 8 uses) if the passed {@code Collection} is one of the
* types listed below.
*
*
* - java.util.ArrayList
* - java.util.Arrays.ArrayList
* - java.util.ArrayDeque
* - java.util.Vector
* - java.util.LinkedList
* - java.util.HashSet
* - java.util.LinkedHashSet
* - java.util.PriorityQueue
* - java.util.concurrent.ArrayBlockingQueue
* - java.util.concurrent.LinkedBlockingQueue
* - java.util.concurrent.LinkedBlockingDeque
* - java.util.concurrent.PriorityBlockingQueue
* - java.util.concurrent.CopyOnWriteArrayList
* - java.util.concurrent.CopyOnWriteArraySet
* - The collections returned from the java.util.HashMap methods
* #keySet(), #entrySet() and #values()
*
*
*
* Otherwise, if the given collection is a {@link java.util.List}, the
* implementation creates a
* late-binding
* spliterator as follows:
*
* - If the list is an instance of {@link java.util.RandomAccess} then
* the default implementation creates a spliterator that traverses
* elements by invoking the method {@link java.util.List#get}. If
* such invocation results or would result in an
* {@code IndexOutOfBoundsException} then the spliterator will
* fail-fast and throw a {@code ConcurrentModificationException}.
* If the list is also an instance of {@link java.util.AbstractList}
* then the spliterator will use the list's
* {@link java.util.AbstractList#modCount modCount} field to provide
* additional fail-fast behavior.
*
- Otherwise, the default implementation creates a spliterator from
* the list's {@code Iterator}. The spliterator inherits the
* fail-fast properties of the list's iterator.
*
*
*
* The {@code Spliterator}s for {@code CopyOnWriteArrayList} and
* {@code CopyOnWriteArraySet} provide a snapshot of the state of the
* collection when the {@code Stream} was created, otherwise the created
* spliterator is
* late-binding, inherits
* the fail-fast properties of the collection's iterator, and
* implements {@code trySplit} to permit limited parallelism.
*
*
* The created spliterator is only traversed, split, or queried for
* estimated size after the terminal operation of the stream pipeline
* commences.
*
* @param
* Type of elements
* @param c
* The collection
* @return a new possibly parallel {@code Stream}
* @throws NullPointerException
* if the given collection is {@code null}
*/
public static Stream parallelStream(Collection c) {
return stream(Spliterators.spliterator(c), true);
}
/**
* Creates a new sequential {@code Stream} using the given collection's
* {@link java.util.Collection#iterator()} as the source of elements for an
* internally created {@code Spliterator} which will report the collection's
* {@link java.util.Collection#size()} as its initial size.
*
*
* The created spliterator is
* late-binding, inherits
* the fail-fast properties of the collection's iterator, and
* implements {@code trySplit} to permit limited parallelism.
*
*
* The created spliterator is only traversed, split, or queried for
* estimated size after the terminal operation of the stream pipeline
* commences.
*
*
* If the collection is immutable it is recommended to report a
* characteristic of {@code IMMUTABLE}. The characteristics {@code SIZED}
* and {@code SUBSIZED} are additionally (automatically) reported unless
* {@code CONCURRENT} is supplied.
*
* @param
* Type of elements
* @param c
* The collection
* @param characteristics
* Characteristics of the source collection's iterator or
* elements. The characteristics {@code SIZED} and
* {@code SUBSIZED} are additionally reported unless
* {@code CONCURRENT} is supplied.
* @return a new sequential {@code Stream}
* @throws NullPointerException if the given collection is {@code null}
*/
public static Stream stream(Collection c, int characteristics) {
return stream(c, characteristics, false);
}
/**
* Creates a new sequential or parallel {@code Stream} using the given
* collection's {@link java.util.Collection#iterator()} as the source of
* elements for an internally created {@code Spliterator} which will report
* the collection's {@link java.util.Collection#size()} as its initial size.
*
*
* The created spliterator is
* late-binding, inherits
* the fail-fast properties of the collection's iterator, and
* implements {@code trySplit} to permit limited parallelism.
*
*
* The created spliterator is only traversed, split, or queried for
* estimated size after the terminal operation of the stream pipeline
* commences.
*
* If possible for the collection, it is strongly recommended to report a
* characteristic of {@code IMMUTABLE} or {@code CONCURRENT} especially if
* you want a parallel {@code Stream}. The characteristics {@code SIZED} and
* {@code SUBSIZED} are additionally (automatically) reported unless
* {@code CONCURRENT} is supplied.
*
* @param
* Type of elements
* @param c
* The collection
* @param characteristics
* Characteristics of the source collection's iterator or
* elements. The characteristics {@code SIZED} and
* {@code SUBSIZED} are additionally reported unless
* {@code CONCURRENT} is supplied.
* @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}
* @throws NullPointerException if the given collection is {@code null}
*/
public static Stream stream(Collection c, int characteristics, boolean parallel) {
Objects.requireNonNull(c);
return stream(Spliterators.spliterator(c, characteristics), parallel);
}
/**
* Creates a new sequential or parallel {@code Stream} from a
* {@code 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
* {@code IMMUTABLE} or {@code CONCURRENT}, or be
* late-binding. Otherwise,
* {@link #stream(java8.util.function.Supplier, int, boolean)} should be used
* to reduce the scope of potential interference with the source. See
* Non-Interference for
* more details.
*
* @param 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 Stream stream(Spliterator 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}.
*
* 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.
*
*
For spliterators that report a characteristic of {@code IMMUTABLE}
* or {@code CONCURRENT}, or that are
* late-binding, it is likely
* more efficient to use {@link #stream(java8.util.Spliterator, boolean)}
* 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
* Non-Interference for
* more details.
*
* @param 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(java8.util.Spliterator, boolean)
*/
public static Stream stream(Supplier> 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}.
*
* 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
* {@code IMMUTABLE} or {@code CONCURRENT}, or be
* late-binding. Otherwise,
* {@link #intStream(java8.util.function.Supplier, int, boolean)} should be
* used to reduce the scope of potential interference with the source. See
* Non-Interference 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}.
*
*
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.
*
*
For spliterators that report a characteristic of {@code IMMUTABLE}
* or {@code CONCURRENT}, or that are
* late-binding, it is likely
* more efficient to use {@link #intStream(java8.util.Spliterator.OfInt, boolean)}
* 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
* Non-Interference 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(java8.util.Spliterator.OfInt, boolean)
*/
public static IntStream intStream(Supplier 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}.
*
*
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
* {@code IMMUTABLE} or {@code CONCURRENT}, or be
* late-binding. Otherwise,
* {@link #longStream(java8.util.function.Supplier, int, boolean)} should be
* used to reduce the scope of potential interference with the source. See
* Non-Interference 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}.
*
*
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.
*
*
For spliterators that report a characteristic of {@code IMMUTABLE}
* or {@code CONCURRENT}, or that are
* late-binding, it is likely
* more efficient to use {@link #longStream(java8.util.Spliterator.OfLong, boolean)}
* 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
* Non-Interference 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(java8.util.Spliterator.OfLong, boolean)
*/
public static LongStream longStream(Supplier 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}.
*
*
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
* {@code IMMUTABLE} or {@code CONCURRENT}, or be
* late-binding. Otherwise,
* {@link #doubleStream(java8.util.function.Supplier, int, boolean)} should
* be used to reduce the scope of potential interference with the source. See
* Non-Interference 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}.
*
*
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.
*
*
For spliterators that report a characteristic of {@code IMMUTABLE}
* or {@code CONCURRENT}, or that are
* late-binding, it is likely
* more efficient to use {@link #doubleStream(java8.util.Spliterator.OfDouble, boolean)}
* 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
* Non-Interference 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(java8.util.Spliterator.OfDouble, boolean)
*/
public static DoubleStream doubleStream(Supplier supplier,
int characteristics,
boolean parallel) {
return new DoublePipeline.Head<>(supplier,
StreamOpFlag.fromCharacteristics(characteristics),
parallel);
}
static Runnable closeHandler(BaseStream stream) {
return stream::close;
}
}