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streamsupport is a backport of the Java 8 java.util.function (functional interfaces) and
java.util.stream (streams) API for Java 6 / 7 and Android developers
/*
* 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
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*/
package java8.util.stream;
import java8.util.Objects;
import java8.util.function.DoublePredicate;
import java8.util.function.IntPredicate;
import java8.util.function.LongPredicate;
import java8.util.function.Predicate;
import java8.util.function.Supplier;
import java8.util.Spliterator;
/**
* Factory for instances of a short-circuiting {@code TerminalOp} that implement
* quantified predicate matching on the elements of a stream. Supported variants
* include match-all, match-any, and match-none.
*
* @since 1.8
*/
final class MatchOps {
private MatchOps() { }
/**
* Enum describing quantified match options -- all match, any match, none
* match.
*/
enum MatchKind {
/** Do all elements match the predicate? */
ANY(true, true),
/** Do any elements match the predicate? */
ALL(false, false),
/** Do no elements match the predicate? */
NONE(true, false);
private final boolean stopOnPredicateMatches;
private final boolean shortCircuitResult;
private MatchKind(boolean stopOnPredicateMatches,
boolean shortCircuitResult) {
this.stopOnPredicateMatches = stopOnPredicateMatches;
this.shortCircuitResult = shortCircuitResult;
}
}
/**
* Constructs a quantified predicate matcher for a Stream.
*
* @param the type of stream elements
* @param predicate the {@code Predicate} to apply to stream elements
* @param matchKind the kind of quantified match (all, any, none)
* @return a {@code TerminalOp} implementing the desired quantified match
* criteria
*/
public static TerminalOp makeRef(final Predicate predicate,
final MatchKind matchKind) {
Objects.requireNonNull(predicate);
Objects.requireNonNull(matchKind);
class MatchSink extends BooleanTerminalSink {
MatchSink() {
super(matchKind);
}
@Override
public void accept(T t) {
if (!stop && predicate.test(t) == matchKind.stopOnPredicateMatches) {
stop = true;
value = matchKind.shortCircuitResult;
}
}
}
return new MatchOp<>(StreamShape.REFERENCE, matchKind, MatchSink::new);
}
/**
* Constructs a quantified predicate matcher for an {@code IntStream}.
*
* @param predicate the {@code Predicate} to apply to stream elements
* @param matchKind the kind of quantified match (all, any, none)
* @return a {@code TerminalOp} implementing the desired quantified match
* criteria
*/
public static TerminalOp makeInt(final IntPredicate predicate,
final MatchKind matchKind) {
Objects.requireNonNull(predicate);
Objects.requireNonNull(matchKind);
class MatchSink extends BooleanTerminalSink implements Sink.OfInt {
MatchSink() {
super(matchKind);
}
@Override
public void accept(int t) {
if (!stop && predicate.test(t) == matchKind.stopOnPredicateMatches) {
stop = true;
value = matchKind.shortCircuitResult;
}
}
@Override
public void accept(Integer i) {
SinkDefaults.OfInt.accept(this, i);
}
}
return new MatchOp<>(StreamShape.INT_VALUE, matchKind, MatchSink::new);
}
/**
* Constructs a quantified predicate matcher for a {@code LongStream}.
*
* @param predicate the {@code Predicate} to apply to stream elements
* @param matchKind the kind of quantified match (all, any, none)
* @return a {@code TerminalOp} implementing the desired quantified match
* criteria
*/
public static TerminalOp makeLong(final LongPredicate predicate,
final MatchKind matchKind) {
Objects.requireNonNull(predicate);
Objects.requireNonNull(matchKind);
class MatchSink extends BooleanTerminalSink implements Sink.OfLong {
MatchSink() {
super(matchKind);
}
@Override
public void accept(long t) {
if (!stop && predicate.test(t) == matchKind.stopOnPredicateMatches) {
stop = true;
value = matchKind.shortCircuitResult;
}
}
@Override
public void accept(Long i) {
SinkDefaults.OfLong.accept(this, i);
}
}
return new MatchOp<>(StreamShape.LONG_VALUE, matchKind, MatchSink::new);
}
/**
* Constructs a quantified predicate matcher for a {@code DoubleStream}.
*
* @param predicate the {@code Predicate} to apply to stream elements
* @param matchKind the kind of quantified match (all, any, none)
* @return a {@code TerminalOp} implementing the desired quantified match
* criteria
*/
public static TerminalOp makeDouble(final DoublePredicate predicate,
final MatchKind matchKind) {
Objects.requireNonNull(predicate);
Objects.requireNonNull(matchKind);
class MatchSink extends BooleanTerminalSink implements Sink.OfDouble {
MatchSink() {
super(matchKind);
}
@Override
public void accept(double t) {
if (!stop && predicate.test(t) == matchKind.stopOnPredicateMatches) {
stop = true;
value = matchKind.shortCircuitResult;
}
}
@Override
public void accept(Double i) {
SinkDefaults.OfDouble.accept(this, i);
}
}
return new MatchOp<>(StreamShape.DOUBLE_VALUE, matchKind, MatchSink::new);
}
/**
* A short-circuiting {@code TerminalOp} that evaluates a predicate on the
* elements of a stream and determines whether all, any or none of those
* elements match the predicate.
*
* @param the output type of the stream pipeline
*/
private static final class MatchOp implements TerminalOp {
private final StreamShape inputShape;
final MatchKind matchKind;
final Supplier> sinkSupplier;
/**
* Constructs a {@code MatchOp}.
*
* @param shape the output shape of the stream pipeline
* @param matchKind the kind of quantified match (all, any, none)
* @param sinkSupplier {@code Supplier} for a {@code Sink} of the
* appropriate shape which implements the matching operation
*/
MatchOp(StreamShape shape,
MatchKind matchKind,
Supplier> sinkSupplier) {
this.inputShape = shape;
this.matchKind = matchKind;
this.sinkSupplier = sinkSupplier;
}
@Override
public int getOpFlags() {
return StreamOpFlag.IS_SHORT_CIRCUIT | StreamOpFlag.NOT_ORDERED;
}
@Override
public StreamShape inputShape() {
return inputShape;
}
@Override
public Boolean evaluateSequential(PipelineHelper helper,
Spliterator spliterator) {
return helper.wrapAndCopyInto(sinkSupplier.get(), spliterator).getAndClearState();
}
@Override
public Boolean evaluateParallel(PipelineHelper helper,
Spliterator spliterator) {
// Approach for parallel implementation:
// - Decompose as per usual
// - run match on leaf chunks, call result "b"
// - if b == matchKind.shortCircuitOn, complete early and return b
// - else if we complete normally, return !shortCircuitOn
return new MatchTask<>(this, helper, spliterator).invoke();
}
}
/**
* Boolean specific terminal sink to avoid the boxing costs when returning
* results. Subclasses implement the shape-specific functionality.
*
* @param The output type of the stream pipeline
*/
private abstract static class BooleanTerminalSink implements Sink {
boolean stop;
boolean value;
BooleanTerminalSink(MatchKind matchKind) {
value = !matchKind.shortCircuitResult;
}
public boolean getAndClearState() {
return value;
}
@Override
public boolean cancellationRequested() {
return stop;
}
@Override
public void begin(long size) {
}
@Override
public void end() {
}
@Override
public void accept(int value) {
SinkDefaults.accept(this, value);
}
@Override
public void accept(long value) {
SinkDefaults.accept(this, value);
}
@Override
public void accept(double value) {
SinkDefaults.accept(this, value);
}
}
/**
* ForkJoinTask implementation to implement a parallel short-circuiting
* quantified match
*
* @param the type of source elements for the pipeline
* @param the type of output elements for the pipeline
*/
@SuppressWarnings("serial")
private static final class MatchTask
extends AbstractShortCircuitTask> {
private final MatchOp op;
/**
* Constructor for root node
*/
MatchTask(MatchOp op, PipelineHelper helper,
Spliterator spliterator) {
super(helper, spliterator);
this.op = op;
}
/**
* Constructor for non-root node
*/
MatchTask(MatchTask parent, Spliterator spliterator) {
super(parent, spliterator);
this.op = parent.op;
}
@Override
protected MatchTask makeChild(Spliterator spliterator) {
return new MatchTask<>(this, spliterator);
}
@Override
protected Boolean doLeaf() {
boolean b = helper.wrapAndCopyInto(op.sinkSupplier.get(), spliterator).getAndClearState();
if (b == op.matchKind.shortCircuitResult)
shortCircuit(b);
return null;
}
@Override
protected Boolean getEmptyResult() {
return !op.matchKind.shortCircuitResult;
}
}
}
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