99 lines
3.9 KiB
Java
99 lines
3.9 KiB
Java
/*
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* Copyright (c) 2012, 2013, Oracle and/or its affiliates. All rights reserved.
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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*
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* This code is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License version 2 only, as
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* published by the Free Software Foundation. Oracle designates this
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* particular file as subject to the "Classpath" exception as provided
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* by Oracle in the LICENSE file that accompanied this code.
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*
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* This code is distributed in the hope that it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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* version 2 for more details (a copy is included in the LICENSE file that
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* accompanied this code).
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*
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* You should have received a copy of the GNU General Public License version
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* 2 along with this work; if not, write to the Free Software Foundation,
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* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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*
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* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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* or visit www.oracle.com if you need additional information or have any
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* questions.
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*/
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package java.util.stream;
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import java.util.Spliterator;
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/**
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* An operation in a stream pipeline that takes a stream as input and produces
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* a result or side-effect. A {@code TerminalOp} has an input type and stream
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* shape, and a result type. A {@code TerminalOp} also has a set of
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* <em>operation flags</em> that describes how the operation processes elements
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* of the stream (such as short-circuiting or respecting encounter order; see
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* {@link StreamOpFlag}).
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*
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* <p>A {@code TerminalOp} must provide a sequential and parallel implementation
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* of the operation relative to a given stream source and set of intermediate
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* operations.
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*
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* @param <E_IN> the type of input elements
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* @param <R> the type of the result
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* @since 1.8
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*/
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interface TerminalOp<E_IN, R> {
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/**
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* Gets the shape of the input type of this operation.
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*
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* @implSpec The default returns {@code StreamShape.REFERENCE}.
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*
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* @return StreamShape of the input type of this operation
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*/
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default StreamShape inputShape() { return StreamShape.REFERENCE; }
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/**
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* Gets the stream flags of the operation. Terminal operations may set a
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* limited subset of the stream flags defined in {@link StreamOpFlag}, and
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* these flags are combined with the previously combined stream and
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* intermediate operation flags for the pipeline.
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*
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* @implSpec The default implementation returns zero.
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*
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* @return the stream flags for this operation
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* @see StreamOpFlag
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*/
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default int getOpFlags() { return 0; }
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/**
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* Performs a parallel evaluation of the operation using the specified
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* {@code PipelineHelper}, which describes the upstream intermediate
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* operations.
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*
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* @implSpec The default performs a sequential evaluation of the operation
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* using the specified {@code PipelineHelper}.
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*
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* @param helper the pipeline helper
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* @param spliterator the source spliterator
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* @return the result of the evaluation
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*/
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default <P_IN> R evaluateParallel(PipelineHelper<E_IN> helper,
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Spliterator<P_IN> spliterator) {
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if (Tripwire.ENABLED)
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Tripwire.trip(getClass(), "{0} triggering TerminalOp.evaluateParallel serial default");
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return evaluateSequential(helper, spliterator);
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}
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/**
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* Performs a sequential evaluation of the operation using the specified
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* {@code PipelineHelper}, which describes the upstream intermediate
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* operations.
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*
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* @param helper the pipeline helper
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* @param spliterator the source spliterator
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* @return the result of the evaluation
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*/
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<P_IN> R evaluateSequential(PipelineHelper<E_IN> helper,
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Spliterator<P_IN> spliterator);
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}
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