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895 lines
35 KiB
895 lines
35 KiB
/*
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* Copyright (c) 2012, 2013, Oracle and/or its affiliates. All rights reserved.
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* ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
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*
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*
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*
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*
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*
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*
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*
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*
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*/
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package java.util.stream;
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import java.nio.charset.Charset;
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import java.nio.file.Files;
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import java.nio.file.Path;
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import java.util.Arrays;
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import java.util.Collection;
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import java.util.DoubleSummaryStatistics;
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import java.util.Objects;
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import java.util.OptionalDouble;
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import java.util.PrimitiveIterator;
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import java.util.Spliterator;
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import java.util.Spliterators;
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import java.util.concurrent.ConcurrentHashMap;
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import java.util.function.BiConsumer;
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import java.util.function.DoubleBinaryOperator;
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import java.util.function.DoubleConsumer;
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import java.util.function.DoubleFunction;
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import java.util.function.DoublePredicate;
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import java.util.function.DoubleSupplier;
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import java.util.function.DoubleToIntFunction;
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import java.util.function.DoubleToLongFunction;
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import java.util.function.DoubleUnaryOperator;
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import java.util.function.Function;
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import java.util.function.ObjDoubleConsumer;
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import java.util.function.Supplier;
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/**
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* A sequence of primitive double-valued elements supporting sequential and parallel
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* aggregate operations. This is the {@code double} primitive specialization of
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* {@link Stream}.
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*
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* <p>The following example illustrates an aggregate operation using
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* {@link Stream} and {@link DoubleStream}, computing the sum of the weights of the
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* red widgets:
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*
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* <pre>{@code
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* double sum = widgets.stream()
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* .filter(w -> w.getColor() == RED)
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* .mapToDouble(w -> w.getWeight())
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* .sum();
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* }</pre>
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*
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* See the class documentation for {@link Stream} and the package documentation
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* for <a href="package-summary.html">java.util.stream</a> for additional
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* specification of streams, stream operations, stream pipelines, and
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* parallelism.
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*
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* @since 1.8
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* @see Stream
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* @see <a href="package-summary.html">java.util.stream</a>
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*/
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public interface DoubleStream extends BaseStream<Double, DoubleStream> {
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/**
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* Returns a stream consisting of the elements of this stream that match
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* the given predicate.
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*
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* <p>This is an <a href="package-summary.html#StreamOps">intermediate
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* operation</a>.
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*
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* @param predicate a <a href="package-summary.html#NonInterference">non-interfering</a>,
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* <a href="package-summary.html#Statelessness">stateless</a>
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* predicate to apply to each element to determine if it
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* should be included
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* @return the new stream
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*/
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DoubleStream filter(DoublePredicate predicate);
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/**
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* Returns a stream consisting of the results of applying the given
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* function to the elements of this stream.
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*
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* <p>This is an <a href="package-summary.html#StreamOps">intermediate
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* operation</a>.
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*
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* @param mapper a <a href="package-summary.html#NonInterference">non-interfering</a>,
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* <a href="package-summary.html#Statelessness">stateless</a>
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* function to apply to each element
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* @return the new stream
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*/
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DoubleStream map(DoubleUnaryOperator mapper);
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/**
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* Returns an object-valued {@code Stream} consisting of the results of
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* applying the given function to the elements of this stream.
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*
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* <p>This is an <a href="package-summary.html#StreamOps">
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* intermediate operation</a>.
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*
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* @param <U> the element type of the new stream
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* @param mapper a <a href="package-summary.html#NonInterference">non-interfering</a>,
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* <a href="package-summary.html#Statelessness">stateless</a>
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* function to apply to each element
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* @return the new stream
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*/
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<U> Stream<U> mapToObj(DoubleFunction<? extends U> mapper);
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/**
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* Returns an {@code IntStream} consisting of the results of applying the
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* given function to the elements of this stream.
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*
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* <p>This is an <a href="package-summary.html#StreamOps">intermediate
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* operation</a>.
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*
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* @param mapper a <a href="package-summary.html#NonInterference">non-interfering</a>,
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* <a href="package-summary.html#Statelessness">stateless</a>
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* function to apply to each element
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* @return the new stream
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*/
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IntStream mapToInt(DoubleToIntFunction mapper);
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/**
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* Returns a {@code LongStream} consisting of the results of applying the
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* given function to the elements of this stream.
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*
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* <p>This is an <a href="package-summary.html#StreamOps">intermediate
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* operation</a>.
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*
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* @param mapper a <a href="package-summary.html#NonInterference">non-interfering</a>,
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* <a href="package-summary.html#Statelessness">stateless</a>
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* function to apply to each element
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* @return the new stream
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*/
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LongStream mapToLong(DoubleToLongFunction mapper);
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/**
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* Returns a stream consisting of the results of replacing each element of
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* this stream with the contents of a mapped stream produced by applying
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* the provided mapping function to each element. Each mapped stream is
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* {@link java.util.stream.BaseStream#close() closed} after its contents
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* have been placed into this stream. (If a mapped stream is {@code null}
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* an empty stream is used, instead.)
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*
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* <p>This is an <a href="package-summary.html#StreamOps">intermediate
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* operation</a>.
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*
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* @param mapper a <a href="package-summary.html#NonInterference">non-interfering</a>,
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* <a href="package-summary.html#Statelessness">stateless</a>
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* function to apply to each element which produces a
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* {@code DoubleStream} of new values
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* @return the new stream
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* @see Stream#flatMap(Function)
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*/
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DoubleStream flatMap(DoubleFunction<? extends DoubleStream> mapper);
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/**
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* Returns a stream consisting of the distinct elements of this stream. The
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* elements are compared for equality according to
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* {@link java.lang.Double#compare(double, double)}.
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*
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* <p>This is a <a href="package-summary.html#StreamOps">stateful
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* intermediate operation</a>.
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*
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* @return the result stream
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*/
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DoubleStream distinct();
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/**
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* Returns a stream consisting of the elements of this stream in sorted
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* order. The elements are compared for equality according to
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* {@link java.lang.Double#compare(double, double)}.
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*
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* <p>This is a <a href="package-summary.html#StreamOps">stateful
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* intermediate operation</a>.
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*
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* @return the result stream
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*/
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DoubleStream sorted();
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/**
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* Returns a stream consisting of the elements of this stream, additionally
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* performing the provided action on each element as elements are consumed
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* from the resulting stream.
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*
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* <p>This is an <a href="package-summary.html#StreamOps">intermediate
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* operation</a>.
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*
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* <p>For parallel stream pipelines, the action may be called at
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* whatever time and in whatever thread the element is made available by the
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* upstream operation. If the action modifies shared state,
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* it is responsible for providing the required synchronization.
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*
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* @apiNote This method exists mainly to support debugging, where you want
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* to see the elements as they flow past a certain point in a pipeline:
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* <pre>{@code
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* DoubleStream.of(1, 2, 3, 4)
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* .filter(e -> e > 2)
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* .peek(e -> System.out.println("Filtered value: " + e))
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* .map(e -> e * e)
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* .peek(e -> System.out.println("Mapped value: " + e))
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* .sum();
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* }</pre>
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*
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* @param action a <a href="package-summary.html#NonInterference">
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* non-interfering</a> action to perform on the elements as
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* they are consumed from the stream
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* @return the new stream
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*/
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DoubleStream peek(DoubleConsumer action);
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/**
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* Returns a stream consisting of the elements of this stream, truncated
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* to be no longer than {@code maxSize} in length.
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*
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* <p>This is a <a href="package-summary.html#StreamOps">short-circuiting
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* stateful intermediate operation</a>.
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*
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* @apiNote
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* While {@code limit()} is generally a cheap operation on sequential
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* stream pipelines, it can be quite expensive on ordered parallel pipelines,
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* especially for large values of {@code maxSize}, since {@code limit(n)}
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* is constrained to return not just any <em>n</em> elements, but the
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* <em>first n</em> elements in the encounter order. Using an unordered
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* stream source (such as {@link #generate(DoubleSupplier)}) or removing the
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* ordering constraint with {@link #unordered()} may result in significant
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* speedups of {@code limit()} in parallel pipelines, if the semantics of
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* your situation permit. If consistency with encounter order is required,
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* and you are experiencing poor performance or memory utilization with
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* {@code limit()} in parallel pipelines, switching to sequential execution
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* with {@link #sequential()} may improve performance.
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*
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* @param maxSize the number of elements the stream should be limited to
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* @return the new stream
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* @throws IllegalArgumentException if {@code maxSize} is negative
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*/
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DoubleStream limit(long maxSize);
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/**
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* Returns a stream consisting of the remaining elements of this stream
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* after discarding the first {@code n} elements of the stream.
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* If this stream contains fewer than {@code n} elements then an
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* empty stream will be returned.
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*
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* <p>This is a <a href="package-summary.html#StreamOps">stateful
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* intermediate operation</a>.
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*
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* @apiNote
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* While {@code skip()} is generally a cheap operation on sequential
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* stream pipelines, it can be quite expensive on ordered parallel pipelines,
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* especially for large values of {@code n}, since {@code skip(n)}
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* is constrained to skip not just any <em>n</em> elements, but the
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* <em>first n</em> elements in the encounter order. Using an unordered
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* stream source (such as {@link #generate(DoubleSupplier)}) or removing the
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* ordering constraint with {@link #unordered()} may result in significant
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* speedups of {@code skip()} in parallel pipelines, if the semantics of
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* your situation permit. If consistency with encounter order is required,
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* and you are experiencing poor performance or memory utilization with
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* {@code skip()} in parallel pipelines, switching to sequential execution
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* with {@link #sequential()} may improve performance.
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*
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* @param n the number of leading elements to skip
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* @return the new stream
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* @throws IllegalArgumentException if {@code n} is negative
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*/
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DoubleStream skip(long n);
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/**
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* Performs an action for each element of this stream.
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*
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* <p>This is a <a href="package-summary.html#StreamOps">terminal
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* operation</a>.
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*
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* <p>For parallel stream pipelines, this operation does <em>not</em>
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* guarantee to respect the encounter order of the stream, as doing so
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* would sacrifice the benefit of parallelism. For any given element, the
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* action may be performed at whatever time and in whatever thread the
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* library chooses. If the action accesses shared state, it is
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* responsible for providing the required synchronization.
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*
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* @param action a <a href="package-summary.html#NonInterference">
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* non-interfering</a> action to perform on the elements
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*/
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void forEach(DoubleConsumer action);
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/**
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* Performs an action for each element of this stream, guaranteeing that
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* each element is processed in encounter order for streams that have a
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* defined encounter order.
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*
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* <p>This is a <a href="package-summary.html#StreamOps">terminal
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* operation</a>.
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*
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* @param action a <a href="package-summary.html#NonInterference">
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* non-interfering</a> action to perform on the elements
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* @see #forEach(DoubleConsumer)
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*/
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void forEachOrdered(DoubleConsumer action);
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/**
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* Returns an array containing the elements of this stream.
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*
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* <p>This is a <a href="package-summary.html#StreamOps">terminal
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* operation</a>.
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*
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* @return an array containing the elements of this stream
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*/
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double[] toArray();
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/**
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* Performs a <a href="package-summary.html#Reduction">reduction</a> on the
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* elements of this stream, using the provided identity value and an
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* <a href="package-summary.html#Associativity">associative</a>
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* accumulation function, and returns the reduced value. This is equivalent
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* to:
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* <pre>{@code
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* double result = identity;
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* for (double element : this stream)
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* result = accumulator.applyAsDouble(result, element)
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* return result;
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* }</pre>
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*
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* but is not constrained to execute sequentially.
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*
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* <p>The {@code identity} value must be an identity for the accumulator
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* function. This means that for all {@code x},
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* {@code accumulator.apply(identity, x)} is equal to {@code x}.
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* The {@code accumulator} function must be an
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* <a href="package-summary.html#Associativity">associative</a> function.
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*
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* <p>This is a <a href="package-summary.html#StreamOps">terminal
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* operation</a>.
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*
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* @apiNote Sum, min, max, and average are all special cases of reduction.
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* Summing a stream of numbers can be expressed as:
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* <pre>{@code
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* double sum = numbers.reduce(0, (a, b) -> a+b);
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* }</pre>
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*
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* or more compactly:
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*
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* <pre>{@code
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* double sum = numbers.reduce(0, Double::sum);
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* }</pre>
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*
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* <p>While this may seem a more roundabout way to perform an aggregation
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* compared to simply mutating a running total in a loop, reduction
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* operations parallelize more gracefully, without needing additional
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* synchronization and with greatly reduced risk of data races.
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*
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* @param identity the identity value for the accumulating function
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* @param op an <a href="package-summary.html#Associativity">associative</a>,
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* <a href="package-summary.html#NonInterference">non-interfering</a>,
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* <a href="package-summary.html#Statelessness">stateless</a>
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* function for combining two values
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* @return the result of the reduction
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* @see #sum()
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* @see #min()
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* @see #max()
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* @see #average()
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*/
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double reduce(double identity, DoubleBinaryOperator op);
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/**
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* Performs a <a href="package-summary.html#Reduction">reduction</a> on the
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* elements of this stream, using an
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* <a href="package-summary.html#Associativity">associative</a> accumulation
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* function, and returns an {@code OptionalDouble} describing the reduced
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* value, if any. This is equivalent to:
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* <pre>{@code
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* boolean foundAny = false;
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* double result = null;
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* for (double element : this stream) {
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* if (!foundAny) {
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* foundAny = true;
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* result = element;
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* }
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* else
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* result = accumulator.applyAsDouble(result, element);
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* }
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* return foundAny ? OptionalDouble.of(result) : OptionalDouble.empty();
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* }</pre>
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*
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* but is not constrained to execute sequentially.
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*
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* <p>The {@code accumulator} function must be an
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* <a href="package-summary.html#Associativity">associative</a> function.
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*
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* <p>This is a <a href="package-summary.html#StreamOps">terminal
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* operation</a>.
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*
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* @param op an <a href="package-summary.html#Associativity">associative</a>,
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* <a href="package-summary.html#NonInterference">non-interfering</a>,
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* <a href="package-summary.html#Statelessness">stateless</a>
|
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* function for combining two values
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* @return the result of the reduction
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* @see #reduce(double, DoubleBinaryOperator)
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*/
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OptionalDouble reduce(DoubleBinaryOperator op);
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/**
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* Performs a <a href="package-summary.html#MutableReduction">mutable
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* reduction</a> operation on the elements of this stream. A mutable
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* reduction is one in which the reduced value is a mutable result container,
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* such as an {@code ArrayList}, and elements are incorporated by updating
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* the state of the result rather than by replacing the result. This
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* produces a result equivalent to:
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* <pre>{@code
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* R result = supplier.get();
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* for (double element : this stream)
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* accumulator.accept(result, element);
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* return result;
|
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* }</pre>
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*
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* <p>Like {@link #reduce(double, DoubleBinaryOperator)}, {@code collect}
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* operations can be parallelized without requiring additional
|
|
* synchronization.
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*
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* <p>This is a <a href="package-summary.html#StreamOps">terminal
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* operation</a>.
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*
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* @param <R> type of the result
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* @param supplier a function that creates a new result container. For a
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* parallel execution, this function may be called
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* multiple times and must return a fresh value each time.
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* @param accumulator an <a href="package-summary.html#Associativity">associative</a>,
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* <a href="package-summary.html#NonInterference">non-interfering</a>,
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* <a href="package-summary.html#Statelessness">stateless</a>
|
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* function for incorporating an additional element into a result
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* @param combiner an <a href="package-summary.html#Associativity">associative</a>,
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* <a href="package-summary.html#NonInterference">non-interfering</a>,
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* <a href="package-summary.html#Statelessness">stateless</a>
|
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* function for combining two values, which must be
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* compatible with the accumulator function
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* @return the result of the reduction
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* @see Stream#collect(Supplier, BiConsumer, BiConsumer)
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*/
|
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<R> R collect(Supplier<R> supplier,
|
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ObjDoubleConsumer<R> accumulator,
|
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BiConsumer<R, R> combiner);
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|
|
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/**
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* Returns the sum of elements in this stream.
|
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*
|
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* Summation is a special case of a <a
|
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* href="package-summary.html#Reduction">reduction</a>. If
|
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* floating-point summation were exact, this method would be
|
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* equivalent to:
|
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*
|
|
* <pre>{@code
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|
* return reduce(0, Double::sum);
|
|
* }</pre>
|
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*
|
|
* However, since floating-point summation is not exact, the above
|
|
* code is not necessarily equivalent to the summation computation
|
|
* done by this method.
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*
|
|
* <p>If any stream element is a NaN or the sum is at any point a NaN
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|
* then the sum will be NaN.
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|
*
|
|
* The value of a floating-point sum is a function both
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* of the input values as well as the order of addition
|
|
* operations. The order of addition operations of this method is
|
|
* intentionally not defined to allow for implementation
|
|
* flexibility to improve the speed and accuracy of the computed
|
|
* result.
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*
|
|
* In particular, this method may be implemented using compensated
|
|
* summation or other technique to reduce the error bound in the
|
|
* numerical sum compared to a simple summation of {@code double}
|
|
* values.
|
|
*
|
|
* <p>This is a <a href="package-summary.html#StreamOps">terminal
|
|
* operation</a>.
|
|
*
|
|
* @apiNote Elements sorted by increasing absolute magnitude tend
|
|
* to yield more accurate results.
|
|
*
|
|
* @return the sum of elements in this stream
|
|
*/
|
|
double sum();
|
|
|
|
/**
|
|
* Returns an {@code OptionalDouble} describing the minimum element of this
|
|
* stream, or an empty OptionalDouble if this stream is empty. The minimum
|
|
* element will be {@code Double.NaN} if any stream element was NaN. Unlike
|
|
* the numerical comparison operators, this method considers negative zero
|
|
* to be strictly smaller than positive zero. This is a special case of a
|
|
* <a href="package-summary.html#Reduction">reduction</a> and is
|
|
* equivalent to:
|
|
* <pre>{@code
|
|
* return reduce(Double::min);
|
|
* }</pre>
|
|
*
|
|
* <p>This is a <a href="package-summary.html#StreamOps">terminal
|
|
* operation</a>.
|
|
*
|
|
* @return an {@code OptionalDouble} containing the minimum element of this
|
|
* stream, or an empty optional if the stream is empty
|
|
*/
|
|
OptionalDouble min();
|
|
|
|
/**
|
|
* Returns an {@code OptionalDouble} describing the maximum element of this
|
|
* stream, or an empty OptionalDouble if this stream is empty. The maximum
|
|
* element will be {@code Double.NaN} if any stream element was NaN. Unlike
|
|
* the numerical comparison operators, this method considers negative zero
|
|
* to be strictly smaller than positive zero. This is a
|
|
* special case of a
|
|
* <a href="package-summary.html#Reduction">reduction</a> and is
|
|
* equivalent to:
|
|
* <pre>{@code
|
|
* return reduce(Double::max);
|
|
* }</pre>
|
|
*
|
|
* <p>This is a <a href="package-summary.html#StreamOps">terminal
|
|
* operation</a>.
|
|
*
|
|
* @return an {@code OptionalDouble} containing the maximum element of this
|
|
* stream, or an empty optional if the stream is empty
|
|
*/
|
|
OptionalDouble max();
|
|
|
|
/**
|
|
* Returns the count of elements in this stream. This is a special case of
|
|
* a <a href="package-summary.html#Reduction">reduction</a> and is
|
|
* equivalent to:
|
|
* <pre>{@code
|
|
* return mapToLong(e -> 1L).sum();
|
|
* }</pre>
|
|
*
|
|
* <p>This is a <a href="package-summary.html#StreamOps">terminal operation</a>.
|
|
*
|
|
* @return the count of elements in this stream
|
|
*/
|
|
long count();
|
|
|
|
/**
|
|
* Returns an {@code OptionalDouble} describing the arithmetic
|
|
* mean of elements of this stream, or an empty optional if this
|
|
* stream is empty.
|
|
*
|
|
* If any recorded value is a NaN or the sum is at any point a NaN
|
|
* then the average will be NaN.
|
|
*
|
|
* <p>The average returned can vary depending upon the order in
|
|
* which values are recorded.
|
|
*
|
|
* This method may be implemented using compensated summation or
|
|
* other technique to reduce the error bound in the {@link #sum
|
|
* numerical sum} used to compute the average.
|
|
*
|
|
* <p>The average is a special case of a <a
|
|
* href="package-summary.html#Reduction">reduction</a>.
|
|
*
|
|
* <p>This is a <a href="package-summary.html#StreamOps">terminal
|
|
* operation</a>.
|
|
*
|
|
* @apiNote Elements sorted by increasing absolute magnitude tend
|
|
* to yield more accurate results.
|
|
*
|
|
* @return an {@code OptionalDouble} containing the average element of this
|
|
* stream, or an empty optional if the stream is empty
|
|
*/
|
|
OptionalDouble average();
|
|
|
|
/**
|
|
* Returns a {@code DoubleSummaryStatistics} describing various summary data
|
|
* about the elements of this stream. This is a special
|
|
* case of a <a href="package-summary.html#Reduction">reduction</a>.
|
|
*
|
|
* <p>This is a <a href="package-summary.html#StreamOps">terminal
|
|
* operation</a>.
|
|
*
|
|
* @return a {@code DoubleSummaryStatistics} describing various summary data
|
|
* about the elements of this stream
|
|
*/
|
|
DoubleSummaryStatistics summaryStatistics();
|
|
|
|
/**
|
|
* Returns whether any elements of this stream match the provided
|
|
* predicate. May not evaluate the predicate on all elements if not
|
|
* necessary for determining the result. If the stream is empty then
|
|
* {@code false} is returned and the predicate is not evaluated.
|
|
*
|
|
* <p>This is a <a href="package-summary.html#StreamOps">short-circuiting
|
|
* terminal operation</a>.
|
|
*
|
|
* @apiNote
|
|
* This method evaluates the <em>existential quantification</em> of the
|
|
* predicate over the elements of the stream (for some x P(x)).
|
|
*
|
|
* @param predicate a <a href="package-summary.html#NonInterference">non-interfering</a>,
|
|
* <a href="package-summary.html#Statelessness">stateless</a>
|
|
* predicate to apply to elements of this stream
|
|
* @return {@code true} if any elements of the stream match the provided
|
|
* predicate, otherwise {@code false}
|
|
*/
|
|
boolean anyMatch(DoublePredicate predicate);
|
|
|
|
/**
|
|
* Returns whether all elements of this stream match the provided predicate.
|
|
* May not evaluate the predicate on all elements if not necessary for
|
|
* determining the result. If the stream is empty then {@code true} is
|
|
* returned and the predicate is not evaluated.
|
|
*
|
|
* <p>This is a <a href="package-summary.html#StreamOps">short-circuiting
|
|
* terminal operation</a>.
|
|
*
|
|
* @apiNote
|
|
* This method evaluates the <em>universal quantification</em> of the
|
|
* predicate over the elements of the stream (for all x P(x)). If the
|
|
* stream is empty, the quantification is said to be <em>vacuously
|
|
* satisfied</em> and is always {@code true} (regardless of P(x)).
|
|
*
|
|
* @param predicate a <a href="package-summary.html#NonInterference">non-interfering</a>,
|
|
* <a href="package-summary.html#Statelessness">stateless</a>
|
|
* predicate to apply to elements of this stream
|
|
* @return {@code true} if either all elements of the stream match the
|
|
* provided predicate or the stream is empty, otherwise {@code false}
|
|
*/
|
|
boolean allMatch(DoublePredicate predicate);
|
|
|
|
/**
|
|
* Returns whether no elements of this stream match the provided predicate.
|
|
* May not evaluate the predicate on all elements if not necessary for
|
|
* determining the result. If the stream is empty then {@code true} is
|
|
* returned and the predicate is not evaluated.
|
|
*
|
|
* <p>This is a <a href="package-summary.html#StreamOps">short-circuiting
|
|
* terminal operation</a>.
|
|
*
|
|
* @apiNote
|
|
* This method evaluates the <em>universal quantification</em> of the
|
|
* negated predicate over the elements of the stream (for all x ~P(x)). If
|
|
* the stream is empty, the quantification is said to be vacuously satisfied
|
|
* and is always {@code true}, regardless of P(x).
|
|
*
|
|
* @param predicate a <a href="package-summary.html#NonInterference">non-interfering</a>,
|
|
* <a href="package-summary.html#Statelessness">stateless</a>
|
|
* predicate to apply to elements of this stream
|
|
* @return {@code true} if either no elements of the stream match the
|
|
* provided predicate or the stream is empty, otherwise {@code false}
|
|
*/
|
|
boolean noneMatch(DoublePredicate predicate);
|
|
|
|
/**
|
|
* Returns an {@link OptionalDouble} describing the first element of this
|
|
* stream, or an empty {@code OptionalDouble} if the stream is empty. If
|
|
* the stream has no encounter order, then any element may be returned.
|
|
*
|
|
* <p>This is a <a href="package-summary.html#StreamOps">short-circuiting
|
|
* terminal operation</a>.
|
|
*
|
|
* @return an {@code OptionalDouble} describing the first element of this
|
|
* stream, or an empty {@code OptionalDouble} if the stream is empty
|
|
*/
|
|
OptionalDouble findFirst();
|
|
|
|
/**
|
|
* Returns an {@link OptionalDouble} describing some element of the stream,
|
|
* or an empty {@code OptionalDouble} if the stream is empty.
|
|
*
|
|
* <p>This is a <a href="package-summary.html#StreamOps">short-circuiting
|
|
* terminal operation</a>.
|
|
*
|
|
* <p>The behavior of this operation is explicitly nondeterministic; it is
|
|
* free to select any element in the stream. This is to allow for maximal
|
|
* performance in parallel operations; the cost is that multiple invocations
|
|
* on the same source may not return the same result. (If a stable result
|
|
* is desired, use {@link #findFirst()} instead.)
|
|
*
|
|
* @return an {@code OptionalDouble} describing some element of this stream,
|
|
* or an empty {@code OptionalDouble} if the stream is empty
|
|
* @see #findFirst()
|
|
*/
|
|
OptionalDouble findAny();
|
|
|
|
/**
|
|
* Returns a {@code Stream} consisting of the elements of this stream,
|
|
* boxed to {@code Double}.
|
|
*
|
|
* <p>This is an <a href="package-summary.html#StreamOps">intermediate
|
|
* operation</a>.
|
|
*
|
|
* @return a {@code Stream} consistent of the elements of this stream,
|
|
* each boxed to a {@code Double}
|
|
*/
|
|
Stream<Double> boxed();
|
|
|
|
@Override
|
|
DoubleStream sequential();
|
|
|
|
@Override
|
|
DoubleStream parallel();
|
|
|
|
@Override
|
|
PrimitiveIterator.OfDouble iterator();
|
|
|
|
@Override
|
|
Spliterator.OfDouble spliterator();
|
|
|
|
|
|
// Static factories
|
|
|
|
/**
|
|
* Returns a builder for a {@code DoubleStream}.
|
|
*
|
|
* @return a stream builder
|
|
*/
|
|
public static Builder builder() {
|
|
return new Streams.DoubleStreamBuilderImpl();
|
|
}
|
|
|
|
/**
|
|
* Returns an empty sequential {@code DoubleStream}.
|
|
*
|
|
* @return an empty sequential stream
|
|
*/
|
|
public static DoubleStream empty() {
|
|
return StreamSupport.doubleStream(Spliterators.emptyDoubleSpliterator(), false);
|
|
}
|
|
|
|
/**
|
|
* Returns a sequential {@code DoubleStream} containing a single element.
|
|
*
|
|
* @param t the single element
|
|
* @return a singleton sequential stream
|
|
*/
|
|
public static DoubleStream of(double t) {
|
|
return StreamSupport.doubleStream(new Streams.DoubleStreamBuilderImpl(t), false);
|
|
}
|
|
|
|
/**
|
|
* Returns a sequential ordered stream whose elements are the specified values.
|
|
*
|
|
* @param values the elements of the new stream
|
|
* @return the new stream
|
|
*/
|
|
public static DoubleStream of(double... values) {
|
|
return Arrays.stream(values);
|
|
}
|
|
|
|
/**
|
|
* Returns an infinite sequential ordered {@code DoubleStream} produced by iterative
|
|
* application of a function {@code f} to an initial element {@code seed},
|
|
* producing a {@code Stream} consisting of {@code seed}, {@code f(seed)},
|
|
* {@code f(f(seed))}, etc.
|
|
*
|
|
* <p>The first element (position {@code 0}) in the {@code DoubleStream}
|
|
* will be the provided {@code seed}. For {@code n > 0}, the element at
|
|
* position {@code n}, will be the result of applying the function {@code f}
|
|
* to the element at position {@code n - 1}.
|
|
*
|
|
* @param seed the initial element
|
|
* @param f a function to be applied to to the previous element to produce
|
|
* a new element
|
|
* @return a new sequential {@code DoubleStream}
|
|
*/
|
|
public static DoubleStream iterate(final double seed, final DoubleUnaryOperator f) {
|
|
Objects.requireNonNull(f);
|
|
final PrimitiveIterator.OfDouble iterator = new PrimitiveIterator.OfDouble() {
|
|
double t = seed;
|
|
|
|
@Override
|
|
public boolean hasNext() {
|
|
return true;
|
|
}
|
|
|
|
@Override
|
|
public double nextDouble() {
|
|
double v = t;
|
|
t = f.applyAsDouble(t);
|
|
return v;
|
|
}
|
|
};
|
|
return StreamSupport.doubleStream(Spliterators.spliteratorUnknownSize(
|
|
iterator,
|
|
Spliterator.ORDERED | Spliterator.IMMUTABLE | Spliterator.NONNULL), false);
|
|
}
|
|
|
|
/**
|
|
* Returns an infinite sequential unordered stream where each element is
|
|
* generated by the provided {@code DoubleSupplier}. This is suitable for
|
|
* generating constant streams, streams of random elements, etc.
|
|
*
|
|
* @param s the {@code DoubleSupplier} for generated elements
|
|
* @return a new infinite sequential unordered {@code DoubleStream}
|
|
*/
|
|
public static DoubleStream generate(DoubleSupplier s) {
|
|
Objects.requireNonNull(s);
|
|
return StreamSupport.doubleStream(
|
|
new StreamSpliterators.InfiniteSupplyingSpliterator.OfDouble(Long.MAX_VALUE, s), false);
|
|
}
|
|
|
|
/**
|
|
* Creates a lazily concatenated stream whose elements are all the
|
|
* elements of the first stream followed by all the elements of the
|
|
* second stream. The resulting stream is ordered if both
|
|
* of the input streams are ordered, and parallel if either of the input
|
|
* streams is parallel. When the resulting stream is closed, the close
|
|
* handlers for both input streams are invoked.
|
|
*
|
|
* @implNote
|
|
* Use caution when constructing streams from repeated concatenation.
|
|
* Accessing an element of a deeply concatenated stream can result in deep
|
|
* call chains, or even {@code StackOverflowException}.
|
|
*
|
|
* @param a the first stream
|
|
* @param b the second stream
|
|
* @return the concatenation of the two input streams
|
|
*/
|
|
public static DoubleStream concat(DoubleStream a, DoubleStream b) {
|
|
Objects.requireNonNull(a);
|
|
Objects.requireNonNull(b);
|
|
|
|
Spliterator.OfDouble split = new Streams.ConcatSpliterator.OfDouble(
|
|
a.spliterator(), b.spliterator());
|
|
DoubleStream stream = StreamSupport.doubleStream(split, a.isParallel() || b.isParallel());
|
|
return stream.onClose(Streams.composedClose(a, b));
|
|
}
|
|
|
|
/**
|
|
* A mutable builder for a {@code DoubleStream}.
|
|
*
|
|
* <p>A stream builder has a lifecycle, which starts in a building
|
|
* phase, during which elements can be added, and then transitions to a built
|
|
* phase, after which elements may not be added. The built phase
|
|
* begins when the {@link #build()} method is called, which creates an
|
|
* ordered stream whose elements are the elements that were added to the
|
|
* stream builder, in the order they were added.
|
|
*
|
|
* @see DoubleStream#builder()
|
|
* @since 1.8
|
|
*/
|
|
public interface Builder extends DoubleConsumer {
|
|
|
|
/**
|
|
* Adds an element to the stream being built.
|
|
*
|
|
* @throws IllegalStateException if the builder has already transitioned
|
|
* to the built state
|
|
*/
|
|
@Override
|
|
void accept(double t);
|
|
|
|
/**
|
|
* Adds an element to the stream being built.
|
|
*
|
|
* @implSpec
|
|
* The default implementation behaves as if:
|
|
* <pre>{@code
|
|
* accept(t)
|
|
* return this;
|
|
* }</pre>
|
|
*
|
|
* @param t the element to add
|
|
* @return {@code this} builder
|
|
* @throws IllegalStateException if the builder has already transitioned
|
|
* to the built state
|
|
*/
|
|
default Builder add(double t) {
|
|
accept(t);
|
|
return this;
|
|
}
|
|
|
|
/**
|
|
* Builds the stream, transitioning this builder to the built state.
|
|
* An {@code IllegalStateException} is thrown if there are further
|
|
* attempts to operate on the builder after it has entered the built
|
|
* state.
|
|
*
|
|
* @return the built stream
|
|
* @throws IllegalStateException if the builder has already transitioned
|
|
* to the built state
|
|
*/
|
|
DoubleStream build();
|
|
}
|
|
}
|