| /* |
| * Copyright (c) 2012, 2013, 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.Spliterator; |
| |
| /** |
| * An operation in a stream pipeline that takes a stream as input and produces |
| * a result or side-effect. A {@code TerminalOp} has an input type and stream |
| * shape, and a result type. A {@code TerminalOp} also has a set of |
| * <em>operation flags</em> that describes how the operation processes elements |
| * of the stream (such as short-circuiting or respecting encounter order; see |
| * {@link StreamOpFlag}). |
| * |
| * <p>A {@code TerminalOp} must provide a sequential and parallel implementation |
| * of the operation relative to a given stream source and set of intermediate |
| * operations. |
| * |
| * @param <E_IN> the type of input elements |
| * @param <R> the type of the result |
| * @since 1.8 |
| */ |
| interface TerminalOp<E_IN, R> { |
| /** |
| * Gets the shape of the input type of this operation. |
| * |
| * @implSpec The default returns {@code StreamShape.REFERENCE}. |
| * |
| * @return StreamShape of the input type of this operation |
| */ |
| default StreamShape inputShape() { return StreamShape.REFERENCE; } |
| |
| /** |
| * Gets the stream flags of the operation. Terminal operations may set a |
| * limited subset of the stream flags defined in {@link StreamOpFlag}, and |
| * these flags are combined with the previously combined stream and |
| * intermediate operation flags for the pipeline. |
| * |
| * @implSpec The default implementation returns zero. |
| * |
| * @return the stream flags for this operation |
| * @see StreamOpFlag |
| */ |
| default int getOpFlags() { return 0; } |
| |
| /** |
| * Performs a parallel evaluation of the operation using the specified |
| * {@code PipelineHelper}, which describes the upstream intermediate |
| * operations. |
| * |
| * @implSpec The default performs a sequential evaluation of the operation |
| * using the specified {@code PipelineHelper}. |
| * |
| * @param helper the pipeline helper |
| * @param spliterator the source spliterator |
| * @return the result of the evaluation |
| */ |
| default <P_IN> R evaluateParallel(PipelineHelper<E_IN> helper, |
| Spliterator<P_IN> spliterator) { |
| if (Tripwire.ENABLED) |
| Tripwire.trip(getClass(), "{0} triggering TerminalOp.evaluateParallel serial default"); |
| return evaluateSequential(helper, spliterator); |
| } |
| |
| /** |
| * Performs a sequential evaluation of the operation using the specified |
| * {@code PipelineHelper}, which describes the upstream intermediate |
| * operations. |
| * |
| * @param helper the pipeline helper |
| * @param spliterator the source spliterator |
| * @return the result of the evaluation |
| */ |
| <P_IN> R evaluateSequential(PipelineHelper<E_IN> helper, |
| Spliterator<P_IN> spliterator); |
| } |