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A library jar that provides APIs for Applications written for the Google Android Platform.
/*
* 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.Objects;
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.BiConsumer;
import java.util.function.BiFunction;
import java.util.function.BinaryOperator;
import java.util.function.DoubleBinaryOperator;
import java.util.function.IntBinaryOperator;
import java.util.function.LongBinaryOperator;
import java.util.function.ObjDoubleConsumer;
import java.util.function.ObjIntConsumer;
import java.util.function.ObjLongConsumer;
import java.util.function.Supplier;
/**
* Factory for creating instances of {@code TerminalOp} that implement
* reductions.
*
* @since 1.8
*/
final class ReduceOps {
private ReduceOps() { }
/**
* Constructs a {@code TerminalOp} that implements a functional reduce on
* reference values.
*
* @param the type of the input elements
* @param the type of the result
* @param seed the identity element for the reduction
* @param reducer the accumulating function that incorporates an additional
* input element into the result
* @param combiner the combining function that combines two intermediate
* results
* @return a {@code TerminalOp} implementing the reduction
*/
public static TerminalOp
makeRef(U seed, BiFunction reducer, BinaryOperator combiner) {
Objects.requireNonNull(reducer);
Objects.requireNonNull(combiner);
class ReducingSink extends Box implements AccumulatingSink {
@Override
public void begin(long size) {
state = seed;
}
@Override
public void accept(T t) {
state = reducer.apply(state, t);
}
@Override
public void combine(ReducingSink other) {
state = combiner.apply(state, other.state);
}
}
return new ReduceOp(StreamShape.REFERENCE) {
@Override
public ReducingSink makeSink() {
return new ReducingSink();
}
};
}
/**
* Constructs a {@code TerminalOp} that implements a functional reduce on
* reference values producing an optional reference result.
*
* @param The type of the input elements, and the type of the result
* @param operator The reducing function
* @return A {@code TerminalOp} implementing the reduction
*/
public static TerminalOp>
makeRef(BinaryOperator operator) {
Objects.requireNonNull(operator);
class ReducingSink
implements AccumulatingSink, ReducingSink> {
private boolean empty;
private T state;
public void begin(long size) {
empty = true;
state = null;
}
@Override
public void accept(T t) {
if (empty) {
empty = false;
state = t;
} else {
state = operator.apply(state, t);
}
}
@Override
public Optional get() {
return empty ? Optional.empty() : Optional.of(state);
}
@Override
public void combine(ReducingSink other) {
if (!other.empty)
accept(other.state);
}
}
return new ReduceOp, ReducingSink>(StreamShape.REFERENCE) {
@Override
public ReducingSink makeSink() {
return new ReducingSink();
}
};
}
/**
* Constructs a {@code TerminalOp} that implements a mutable reduce on
* reference values.
*
* @param the type of the input elements
* @param the type of the intermediate reduction result
* @param collector a {@code Collector} defining the reduction
* @return a {@code ReduceOp} implementing the reduction
*/
public static TerminalOp
makeRef(Collector collector) {
Supplier supplier = Objects.requireNonNull(collector).supplier();
BiConsumer accumulator = collector.accumulator();
BinaryOperator combiner = collector.combiner();
class ReducingSink extends Box
implements AccumulatingSink {
@Override
public void begin(long size) {
state = supplier.get();
}
@Override
public void accept(T t) {
accumulator.accept(state, t);
}
@Override
public void combine(ReducingSink other) {
state = combiner.apply(state, other.state);
}
}
return new ReduceOp(StreamShape.REFERENCE) {
@Override
public ReducingSink makeSink() {
return new ReducingSink();
}
@Override
public int getOpFlags() {
return collector.characteristics().contains(Collector.Characteristics.UNORDERED)
? StreamOpFlag.NOT_ORDERED
: 0;
}
};
}
/**
* Constructs a {@code TerminalOp} that implements a mutable reduce on
* reference values.
*
* @param the type of the input elements
* @param the type of the result
* @param seedFactory a factory to produce a new base accumulator
* @param accumulator a function to incorporate an element into an
* accumulator
* @param reducer a function to combine an accumulator into another
* @return a {@code TerminalOp} implementing the reduction
*/
public static TerminalOp
makeRef(Supplier seedFactory,
BiConsumer accumulator,
BiConsumer reducer) {
Objects.requireNonNull(seedFactory);
Objects.requireNonNull(accumulator);
Objects.requireNonNull(reducer);
class ReducingSink extends Box
implements AccumulatingSink {
@Override
public void begin(long size) {
state = seedFactory.get();
}
@Override
public void accept(T t) {
accumulator.accept(state, t);
}
@Override
public void combine(ReducingSink other) {
reducer.accept(state, other.state);
}
}
return new ReduceOp(StreamShape.REFERENCE) {
@Override
public ReducingSink makeSink() {
return new ReducingSink();
}
};
}
/**
* Constructs a {@code TerminalOp} that implements a functional reduce on
* {@code int} values.
*
* @param identity the identity for the combining function
* @param operator the combining function
* @return a {@code TerminalOp} implementing the reduction
*/
public static TerminalOp
makeInt(int identity, IntBinaryOperator operator) {
Objects.requireNonNull(operator);
class ReducingSink
implements AccumulatingSink, Sink.OfInt {
private int state;
@Override
public void begin(long size) {
state = identity;
}
@Override
public void accept(int t) {
state = operator.applyAsInt(state, t);
}
@Override
public Integer get() {
return state;
}
@Override
public void combine(ReducingSink other) {
accept(other.state);
}
}
return new ReduceOp(StreamShape.INT_VALUE) {
@Override
public ReducingSink makeSink() {
return new ReducingSink();
}
};
}
/**
* Constructs a {@code TerminalOp} that implements a functional reduce on
* {@code int} values, producing an optional integer result.
*
* @param operator the combining function
* @return a {@code TerminalOp} implementing the reduction
*/
public static TerminalOp
makeInt(IntBinaryOperator operator) {
Objects.requireNonNull(operator);
class ReducingSink
implements AccumulatingSink, Sink.OfInt {
private boolean empty;
private int state;
public void begin(long size) {
empty = true;
state = 0;
}
@Override
public void accept(int t) {
if (empty) {
empty = false;
state = t;
}
else {
state = operator.applyAsInt(state, t);
}
}
@Override
public OptionalInt get() {
return empty ? OptionalInt.empty() : OptionalInt.of(state);
}
@Override
public void combine(ReducingSink other) {
if (!other.empty)
accept(other.state);
}
}
return new ReduceOp(StreamShape.INT_VALUE) {
@Override
public ReducingSink makeSink() {
return new ReducingSink();
}
};
}
/**
* Constructs a {@code TerminalOp} that implements a mutable reduce on
* {@code int} values.
*
* @param The type of the result
* @param supplier a factory to produce a new accumulator of the result type
* @param accumulator a function to incorporate an int into an
* accumulator
* @param combiner a function to combine an accumulator into another
* @return A {@code ReduceOp} implementing the reduction
*/
public static TerminalOp
makeInt(Supplier supplier,
ObjIntConsumer accumulator,
BinaryOperator combiner) {
Objects.requireNonNull(supplier);
Objects.requireNonNull(accumulator);
Objects.requireNonNull(combiner);
class ReducingSink extends Box
implements AccumulatingSink, Sink.OfInt {
@Override
public void begin(long size) {
state = supplier.get();
}
@Override
public void accept(int t) {
accumulator.accept(state, t);
}
@Override
public void combine(ReducingSink other) {
state = combiner.apply(state, other.state);
}
}
return new ReduceOp(StreamShape.INT_VALUE) {
@Override
public ReducingSink makeSink() {
return new ReducingSink();
}
};
}
/**
* Constructs a {@code TerminalOp} that implements a functional reduce on
* {@code long} values.
*
* @param identity the identity for the combining function
* @param operator the combining function
* @return a {@code TerminalOp} implementing the reduction
*/
public static TerminalOp
makeLong(long identity, LongBinaryOperator operator) {
Objects.requireNonNull(operator);
class ReducingSink
implements AccumulatingSink, Sink.OfLong {
private long state;
@Override
public void begin(long size) {
state = identity;
}
@Override
public void accept(long t) {
state = operator.applyAsLong(state, t);
}
@Override
public Long get() {
return state;
}
@Override
public void combine(ReducingSink other) {
accept(other.state);
}
}
return new ReduceOp(StreamShape.LONG_VALUE) {
@Override
public ReducingSink makeSink() {
return new ReducingSink();
}
};
}
/**
* Constructs a {@code TerminalOp} that implements a functional reduce on
* {@code long} values, producing an optional long result.
*
* @param operator the combining function
* @return a {@code TerminalOp} implementing the reduction
*/
public static TerminalOp
makeLong(LongBinaryOperator operator) {
Objects.requireNonNull(operator);
class ReducingSink
implements AccumulatingSink, Sink.OfLong {
private boolean empty;
private long state;
public void begin(long size) {
empty = true;
state = 0;
}
@Override
public void accept(long t) {
if (empty) {
empty = false;
state = t;
}
else {
state = operator.applyAsLong(state, t);
}
}
@Override
public OptionalLong get() {
return empty ? OptionalLong.empty() : OptionalLong.of(state);
}
@Override
public void combine(ReducingSink other) {
if (!other.empty)
accept(other.state);
}
}
return new ReduceOp(StreamShape.LONG_VALUE) {
@Override
public ReducingSink makeSink() {
return new ReducingSink();
}
};
}
/**
* Constructs a {@code TerminalOp} that implements a mutable reduce on
* {@code long} values.
*
* @param the type of the result
* @param supplier a factory to produce a new accumulator of the result type
* @param accumulator a function to incorporate an int into an
* accumulator
* @param combiner a function to combine an accumulator into another
* @return a {@code TerminalOp} implementing the reduction
*/
public static TerminalOp
makeLong(Supplier supplier,
ObjLongConsumer accumulator,
BinaryOperator combiner) {
Objects.requireNonNull(supplier);
Objects.requireNonNull(accumulator);
Objects.requireNonNull(combiner);
class ReducingSink extends Box
implements AccumulatingSink, Sink.OfLong {
@Override
public void begin(long size) {
state = supplier.get();
}
@Override
public void accept(long t) {
accumulator.accept(state, t);
}
@Override
public void combine(ReducingSink other) {
state = combiner.apply(state, other.state);
}
}
return new ReduceOp(StreamShape.LONG_VALUE) {
@Override
public ReducingSink makeSink() {
return new ReducingSink();
}
};
}
/**
* Constructs a {@code TerminalOp} that implements a functional reduce on
* {@code double} values.
*
* @param identity the identity for the combining function
* @param operator the combining function
* @return a {@code TerminalOp} implementing the reduction
*/
public static TerminalOp
makeDouble(double identity, DoubleBinaryOperator operator) {
Objects.requireNonNull(operator);
class ReducingSink
implements AccumulatingSink, Sink.OfDouble {
private double state;
@Override
public void begin(long size) {
state = identity;
}
@Override
public void accept(double t) {
state = operator.applyAsDouble(state, t);
}
@Override
public Double get() {
return state;
}
@Override
public void combine(ReducingSink other) {
accept(other.state);
}
}
return new ReduceOp(StreamShape.DOUBLE_VALUE) {
@Override
public ReducingSink makeSink() {
return new ReducingSink();
}
};
}
/**
* Constructs a {@code TerminalOp} that implements a functional reduce on
* {@code double} values, producing an optional double result.
*
* @param operator the combining function
* @return a {@code TerminalOp} implementing the reduction
*/
public static TerminalOp
makeDouble(DoubleBinaryOperator operator) {
Objects.requireNonNull(operator);
class ReducingSink
implements AccumulatingSink, Sink.OfDouble {
private boolean empty;
private double state;
public void begin(long size) {
empty = true;
state = 0;
}
@Override
public void accept(double t) {
if (empty) {
empty = false;
state = t;
}
else {
state = operator.applyAsDouble(state, t);
}
}
@Override
public OptionalDouble get() {
return empty ? OptionalDouble.empty() : OptionalDouble.of(state);
}
@Override
public void combine(ReducingSink other) {
if (!other.empty)
accept(other.state);
}
}
return new ReduceOp(StreamShape.DOUBLE_VALUE) {
@Override
public ReducingSink makeSink() {
return new ReducingSink();
}
};
}
/**
* Constructs a {@code TerminalOp} that implements a mutable reduce on
* {@code double} values.
*
* @param the type of the result
* @param supplier a factory to produce a new accumulator of the result type
* @param accumulator a function to incorporate an int into an
* accumulator
* @param combiner a function to combine an accumulator into another
* @return a {@code TerminalOp} implementing the reduction
*/
public static TerminalOp
makeDouble(Supplier supplier,
ObjDoubleConsumer accumulator,
BinaryOperator combiner) {
Objects.requireNonNull(supplier);
Objects.requireNonNull(accumulator);
Objects.requireNonNull(combiner);
class ReducingSink extends Box
implements AccumulatingSink, Sink.OfDouble {
@Override
public void begin(long size) {
state = supplier.get();
}
@Override
public void accept(double t) {
accumulator.accept(state, t);
}
@Override
public void combine(ReducingSink other) {
state = combiner.apply(state, other.state);
}
}
return new ReduceOp(StreamShape.DOUBLE_VALUE) {
@Override
public ReducingSink makeSink() {
return new ReducingSink();
}
};
}
/**
* A type of {@code TerminalSink} that implements an associative reducing
* operation on elements of type {@code T} and producing a result of type
* {@code R}.
*
* @param the type of input element to the combining operation
* @param the result type
* @param the type of the {@code AccumulatingSink}.
*/
private interface AccumulatingSink>
extends TerminalSink {
public void combine(K other);
}
/**
* State box for a single state element, used as a base class for
* {@code AccumulatingSink} instances
*
* @param The type of the state element
*/
private static abstract class Box {
U state;
Box() {} // Avoid creation of special accessor
public U get() {
return state;
}
}
/**
* A {@code TerminalOp} that evaluates a stream pipeline and sends the
* output into an {@code AccumulatingSink}, which performs a reduce
* operation. The {@code AccumulatingSink} must represent an associative
* reducing operation.
*
* @param the output type of the stream pipeline
* @param the result type of the reducing operation
* @param the type of the {@code AccumulatingSink}
*/
private static abstract class ReduceOp>
implements TerminalOp {
private final StreamShape inputShape;
/**
* Create a {@code ReduceOp} of the specified stream shape which uses
* the specified {@code Supplier} to create accumulating sinks.
*
* @param shape The shape of the stream pipeline
*/
ReduceOp(StreamShape shape) {
inputShape = shape;
}
public abstract S makeSink();
@Override
public StreamShape inputShape() {
return inputShape;
}
@Override
public R evaluateSequential(PipelineHelper helper,
Spliterator spliterator) {
return helper.wrapAndCopyInto(makeSink(), spliterator).get();
}
@Override
public R evaluateParallel(PipelineHelper helper,
Spliterator spliterator) {
return new ReduceTask<>(this, helper, spliterator).invoke().get();
}
}
/**
* A {@code ForkJoinTask} for performing a parallel reduce operation.
*/
@SuppressWarnings("serial")
private static final class ReduceTask>
extends AbstractTask> {
private final ReduceOp op;
ReduceTask(ReduceOp op,
PipelineHelper helper,
Spliterator spliterator) {
super(helper, spliterator);
this.op = op;
}
ReduceTask(ReduceTask parent,
Spliterator spliterator) {
super(parent, spliterator);
this.op = parent.op;
}
@Override
protected ReduceTask makeChild(Spliterator spliterator) {
return new ReduceTask<>(this, spliterator);
}
@Override
protected S doLeaf() {
return helper.wrapAndCopyInto(op.makeSink(), spliterator);
}
@Override
public void onCompletion(CountedCompleter caller) {
if (!isLeaf()) {
S leftResult = leftChild.getLocalResult();
leftResult.combine(rightChild.getLocalResult());
setLocalResult(leftResult);
}
// GC spliterator, left and right child
super.onCompletion(caller);
}
}
}