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FindOps.java
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/*
* Copyright (c) 2012, 2013, Oracle and/or its affiliates. All rights reserved.
* ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
*
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package java.util.stream;
import java.util.Optional;
import java.util.OptionalDouble;
import java.util.OptionalInt;
import java.util.OptionalLong;
import java.util.Spliterator;
import java.util.concurrent.CountedCompleter;
import java.util.function.Predicate;
import java.util.function.Supplier;
/**
* Factory for instances of a short-circuiting {@code TerminalOp} that searches
* for an element in a stream pipeline, and terminates when it finds one.
* Supported variants include find-first (find the first element in the
* encounter order) and find-any (find any element, may not be the first in
* encounter order.)
*
* @since 1.8
*/
final class FindOps {
private FindOps() { }
/**
* Constructs a {@code TerminalOp} for streams of objects.
*
* @param <T> the type of elements of the stream
* @param mustFindFirst whether the {@code TerminalOp} must produce the
* first element in the encounter order
* @return a {@code TerminalOp} implementing the find operation
*/
public static <T> TerminalOp<T, Optional<T>> makeRef(boolean mustFindFirst) {
return new FindOp<>(mustFindFirst, StreamShape.REFERENCE, Optional.empty(),
Optional::isPresent, FindSink.OfRef::new);
}
/**
* Constructs a {@code TerminalOp} for streams of ints.
*
* @param mustFindFirst whether the {@code TerminalOp} must produce the
* first element in the encounter order
* @return a {@code TerminalOp} implementing the find operation
*/
public static TerminalOp<Integer, OptionalInt> makeInt(boolean mustFindFirst) {
return new FindOp<>(mustFindFirst, StreamShape.INT_VALUE, OptionalInt.empty(),
OptionalInt::isPresent, FindSink.OfInt::new);
}
/**
* Constructs a {@code TerminalOp} for streams of longs.
*
* @param mustFindFirst whether the {@code TerminalOp} must produce the
* first element in the encounter order
* @return a {@code TerminalOp} implementing the find operation
*/
public static TerminalOp<Long, OptionalLong> makeLong(boolean mustFindFirst) {
return new FindOp<>(mustFindFirst, StreamShape.LONG_VALUE, OptionalLong.empty(),
OptionalLong::isPresent, FindSink.OfLong::new);
}
/**
* Constructs a {@code FindOp} for streams of doubles.
*
* @param mustFindFirst whether the {@code TerminalOp} must produce the
* first element in the encounter order
* @return a {@code TerminalOp} implementing the find operation
*/
public static TerminalOp<Double, OptionalDouble> makeDouble(boolean mustFindFirst) {
return new FindOp<>(mustFindFirst, StreamShape.DOUBLE_VALUE, OptionalDouble.empty(),
OptionalDouble::isPresent, FindSink.OfDouble::new);
}
/**
* A short-circuiting {@code TerminalOp} that searches for an element in a
* stream pipeline, and terminates when it finds one. Implements both
* find-first (find the first element in the encounter order) and find-any
* (find any element, may not be the first in encounter order.)
*
* @param <T> the output type of the stream pipeline
* @param <O> the result type of the find operation, typically an optional
* type
*/
private static final class FindOp<T, O> implements TerminalOp<T, O> {
private final StreamShape shape;
final boolean mustFindFirst;
final O emptyValue;
final Predicate<O> presentPredicate;
final Supplier<TerminalSink<T, O>> sinkSupplier;
/**
* Constructs a {@code FindOp}.
*
* @param mustFindFirst if true, must find the first element in
* encounter order, otherwise can find any element
* @param shape stream shape of elements to search
* @param emptyValue result value corresponding to "found nothing"
* @param presentPredicate {@code Predicate} on result value
* corresponding to "found something"
* @param sinkSupplier supplier for a {@code TerminalSink} implementing
* the matching functionality
*/
FindOp(boolean mustFindFirst,
StreamShape shape,
O emptyValue,
Predicate<O> presentPredicate,
Supplier<TerminalSink<T, O>> sinkSupplier) {
this.mustFindFirst = mustFindFirst;
this.shape = shape;
this.emptyValue = emptyValue;
this.presentPredicate = presentPredicate;
this.sinkSupplier = sinkSupplier;
}
@Override
public int getOpFlags() {
return StreamOpFlag.IS_SHORT_CIRCUIT | (mustFindFirst ? 0 : StreamOpFlag.NOT_ORDERED);
}
@Override
public StreamShape inputShape() {
return shape;
}
@Override
public <S> O evaluateSequential(PipelineHelper<T> helper,
Spliterator<S> spliterator) {
O result = helper.wrapAndCopyInto(sinkSupplier.get(), spliterator).get();
return result != null ? result : emptyValue;
}
@Override
public <P_IN> O evaluateParallel(PipelineHelper<T> helper,
Spliterator<P_IN> spliterator) {
return new FindTask<>(this, helper, spliterator).invoke();
}
}
/**
* Implementation of @{code TerminalSink} that implements the find
* functionality, requesting cancellation when something has been found
*
* @param <T> The type of input element
* @param <O> The result type, typically an optional type
*/
private static abstract class FindSink<T, O> implements TerminalSink<T, O> {
boolean hasValue;
T value;
FindSink() {} // Avoid creation of special accessor
@Override
public void accept(T value) {
if (!hasValue) {
hasValue = true;
this.value = value;
}
}
@Override
public boolean cancellationRequested() {
return hasValue;
}
/** Specialization of {@code FindSink} for reference streams */
static final class OfRef<T> extends FindSink<T, Optional<T>> {
@Override
public Optional<T> get() {
return hasValue ? Optional.of(value) : null;
}
}
/** Specialization of {@code FindSink} for int streams */
static final class OfInt extends FindSink<Integer, OptionalInt>
implements Sink.OfInt {
@Override
public void accept(int value) {
// Boxing is OK here, since few values will actually flow into the sink
accept((Integer) value);
}
@Override
public OptionalInt get() {
return hasValue ? OptionalInt.of(value) : null;
}
}
/** Specialization of {@code FindSink} for long streams */
static final class OfLong extends FindSink<Long, OptionalLong>
implements Sink.OfLong {
@Override
public void accept(long value) {
// Boxing is OK here, since few values will actually flow into the sink
accept((Long) value);
}
@Override
public OptionalLong get() {
return hasValue ? OptionalLong.of(value) : null;
}
}
/** Specialization of {@code FindSink} for double streams */
static final class OfDouble extends FindSink<Double, OptionalDouble>
implements Sink.OfDouble {
@Override
public void accept(double value) {
// Boxing is OK here, since few values will actually flow into the sink
accept((Double) value);
}
@Override
public OptionalDouble get() {
return hasValue ? OptionalDouble.of(value) : null;
}
}
}
/**
* {@code ForkJoinTask} implementing parallel short-circuiting search
* @param <P_IN> Input element type to the stream pipeline
* @param <P_OUT> Output element type from the stream pipeline
* @param <O> Result type from the find operation
*/
@SuppressWarnings("serial")
private static final class FindTask<P_IN, P_OUT, O>
extends AbstractShortCircuitTask<P_IN, P_OUT, O, FindTask<P_IN, P_OUT, O>> {
private final FindOp<P_OUT, O> op;
FindTask(FindOp<P_OUT, O> op,
PipelineHelper<P_OUT> helper,
Spliterator<P_IN> spliterator) {
super(helper, spliterator);
this.op = op;
}
FindTask(FindTask<P_IN, P_OUT, O> parent, Spliterator<P_IN> spliterator) {
super(parent, spliterator);
this.op = parent.op;
}
@Override
protected FindTask<P_IN, P_OUT, O> makeChild(Spliterator<P_IN> spliterator) {
return new FindTask<>(this, spliterator);
}
@Override
protected O getEmptyResult() {
return op.emptyValue;
}
private void foundResult(O answer) {
if (isLeftmostNode())
shortCircuit(answer);
else
cancelLaterNodes();
}
@Override
protected O doLeaf() {
O result = helper.wrapAndCopyInto(op.sinkSupplier.get(), spliterator).get();
if (!op.mustFindFirst) {
if (result != null)
shortCircuit(result);
return null;
}
else {
if (result != null) {
foundResult(result);
return result;
}
else
return null;
}
}
@Override
public void onCompletion(CountedCompleter<?> caller) {
if (op.mustFindFirst) {
for (FindTask<P_IN, P_OUT, O> child = leftChild, p = null; child != p;
p = child, child = rightChild) {
O result = child.getLocalResult();
if (result != null && op.presentPredicate.test(result)) {
setLocalResult(result);
foundResult(result);
break;
}
}
}
super.onCompletion(caller);
}
}
}