/* * 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 * or visit www.oracle.com if you need additional information or have any * questions. */ 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. * *
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}. * *
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}. *
* 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(Supplier, int)} should be used to
* reduce the scope of potential interference with the source. See
* Non-Interference for
* more details.
*
* @param spliterator A {@code Spliterator} describing the stream elements
* @param
* 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(Supplier, int)} should be used to
* reduce the scope of potential interference with the source. See
* Non-Interference for
* more details.
*
* @param spliterator A {@code Spliterator} describing the stream elements
* @param
* 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.
*
* 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(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
* Non-Interference for
* more details.
*
* @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()}
* @param
* 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.
*
* 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(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
* Non-Interference for
* more details.
*
* @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()}
* @param
* 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(Supplier, int)}} 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
* @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}.
*
* 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(Supplier, int)}} 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
* @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}.
*
* 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.
*
* 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(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
* 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 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}.
*
* 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.
*
* 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(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
* 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 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}.
*
* 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(Supplier, int)} 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
* @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}.
*
* 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(Supplier, int)} 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
* @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}.
*
* 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.
*
* 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(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
* 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 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}.
*
* 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.
*
* 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(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
* 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 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}.
*
* 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(Supplier, int)} 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
* @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}.
*
* 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(Supplier, int)} 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
* @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}.
*
* 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.
*
* 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(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
* 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 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}.
*
* 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.
*
* 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(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
* 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 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);
}
}