--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/jdk/src/java.base/share/classes/java/util/stream/ReduceOps.java Sun Aug 17 15:54:13 2014 +0100
@@ -0,0 +1,761 @@
+/*
+ * 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 <T> the type of the input elements
+ * @param <U> 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 <T, U> TerminalOp<T, U>
+ makeRef(U seed, BiFunction<U, ? super T, U> reducer, BinaryOperator<U> combiner) {
+ Objects.requireNonNull(reducer);
+ Objects.requireNonNull(combiner);
+ class ReducingSink extends Box<U> implements AccumulatingSink<T, U, ReducingSink> {
+ @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<T, U, ReducingSink>(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 <T> 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 <T> TerminalOp<T, Optional<T>>
+ makeRef(BinaryOperator<T> operator) {
+ Objects.requireNonNull(operator);
+ class ReducingSink
+ implements AccumulatingSink<T, Optional<T>, 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<T> get() {
+ return empty ? Optional.empty() : Optional.of(state);
+ }
+
+ @Override
+ public void combine(ReducingSink other) {
+ if (!other.empty)
+ accept(other.state);
+ }
+ }
+ return new ReduceOp<T, Optional<T>, ReducingSink>(StreamShape.REFERENCE) {
+ @Override
+ public ReducingSink makeSink() {
+ return new ReducingSink();
+ }
+ };
+ }
+
+ /**
+ * Constructs a {@code TerminalOp} that implements a mutable reduce on
+ * reference values.
+ *
+ * @param <T> the type of the input elements
+ * @param <I> the type of the intermediate reduction result
+ * @param collector a {@code Collector} defining the reduction
+ * @return a {@code ReduceOp} implementing the reduction
+ */
+ public static <T, I> TerminalOp<T, I>
+ makeRef(Collector<? super T, I, ?> collector) {
+ Supplier<I> supplier = Objects.requireNonNull(collector).supplier();
+ BiConsumer<I, ? super T> accumulator = collector.accumulator();
+ BinaryOperator<I> combiner = collector.combiner();
+ class ReducingSink extends Box<I>
+ implements AccumulatingSink<T, I, ReducingSink> {
+ @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<T, I, ReducingSink>(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 <T> the type of the input elements
+ * @param <R> 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 <T, R> TerminalOp<T, R>
+ makeRef(Supplier<R> seedFactory,
+ BiConsumer<R, ? super T> accumulator,
+ BiConsumer<R,R> reducer) {
+ Objects.requireNonNull(seedFactory);
+ Objects.requireNonNull(accumulator);
+ Objects.requireNonNull(reducer);
+ class ReducingSink extends Box<R>
+ implements AccumulatingSink<T, R, ReducingSink> {
+ @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<T, R, ReducingSink>(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<Integer, Integer>
+ makeInt(int identity, IntBinaryOperator operator) {
+ Objects.requireNonNull(operator);
+ class ReducingSink
+ implements AccumulatingSink<Integer, Integer, ReducingSink>, 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<Integer, Integer, ReducingSink>(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<Integer, OptionalInt>
+ makeInt(IntBinaryOperator operator) {
+ Objects.requireNonNull(operator);
+ class ReducingSink
+ implements AccumulatingSink<Integer, OptionalInt, ReducingSink>, 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<Integer, OptionalInt, ReducingSink>(StreamShape.INT_VALUE) {
+ @Override
+ public ReducingSink makeSink() {
+ return new ReducingSink();
+ }
+ };
+ }
+
+ /**
+ * Constructs a {@code TerminalOp} that implements a mutable reduce on
+ * {@code int} values.
+ *
+ * @param <R> 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 <R> TerminalOp<Integer, R>
+ makeInt(Supplier<R> supplier,
+ ObjIntConsumer<R> accumulator,
+ BinaryOperator<R> combiner) {
+ Objects.requireNonNull(supplier);
+ Objects.requireNonNull(accumulator);
+ Objects.requireNonNull(combiner);
+ class ReducingSink extends Box<R>
+ implements AccumulatingSink<Integer, R, ReducingSink>, 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<Integer, R, ReducingSink>(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<Long, Long>
+ makeLong(long identity, LongBinaryOperator operator) {
+ Objects.requireNonNull(operator);
+ class ReducingSink
+ implements AccumulatingSink<Long, Long, ReducingSink>, 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<Long, Long, ReducingSink>(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<Long, OptionalLong>
+ makeLong(LongBinaryOperator operator) {
+ Objects.requireNonNull(operator);
+ class ReducingSink
+ implements AccumulatingSink<Long, OptionalLong, ReducingSink>, 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<Long, OptionalLong, ReducingSink>(StreamShape.LONG_VALUE) {
+ @Override
+ public ReducingSink makeSink() {
+ return new ReducingSink();
+ }
+ };
+ }
+
+ /**
+ * Constructs a {@code TerminalOp} that implements a mutable reduce on
+ * {@code long} values.
+ *
+ * @param <R> 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 <R> TerminalOp<Long, R>
+ makeLong(Supplier<R> supplier,
+ ObjLongConsumer<R> accumulator,
+ BinaryOperator<R> combiner) {
+ Objects.requireNonNull(supplier);
+ Objects.requireNonNull(accumulator);
+ Objects.requireNonNull(combiner);
+ class ReducingSink extends Box<R>
+ implements AccumulatingSink<Long, R, ReducingSink>, 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<Long, R, ReducingSink>(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<Double, Double>
+ makeDouble(double identity, DoubleBinaryOperator operator) {
+ Objects.requireNonNull(operator);
+ class ReducingSink
+ implements AccumulatingSink<Double, Double, ReducingSink>, 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<Double, Double, ReducingSink>(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<Double, OptionalDouble>
+ makeDouble(DoubleBinaryOperator operator) {
+ Objects.requireNonNull(operator);
+ class ReducingSink
+ implements AccumulatingSink<Double, OptionalDouble, ReducingSink>, 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<Double, OptionalDouble, ReducingSink>(StreamShape.DOUBLE_VALUE) {
+ @Override
+ public ReducingSink makeSink() {
+ return new ReducingSink();
+ }
+ };
+ }
+
+ /**
+ * Constructs a {@code TerminalOp} that implements a mutable reduce on
+ * {@code double} values.
+ *
+ * @param <R> 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 <R> TerminalOp<Double, R>
+ makeDouble(Supplier<R> supplier,
+ ObjDoubleConsumer<R> accumulator,
+ BinaryOperator<R> combiner) {
+ Objects.requireNonNull(supplier);
+ Objects.requireNonNull(accumulator);
+ Objects.requireNonNull(combiner);
+ class ReducingSink extends Box<R>
+ implements AccumulatingSink<Double, R, ReducingSink>, 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<Double, R, ReducingSink>(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 <T> the type of input element to the combining operation
+ * @param <R> the result type
+ * @param <K> the type of the {@code AccumulatingSink}.
+ */
+ private interface AccumulatingSink<T, R, K extends AccumulatingSink<T, R, K>>
+ extends TerminalSink<T, R> {
+ public void combine(K other);
+ }
+
+ /**
+ * State box for a single state element, used as a base class for
+ * {@code AccumulatingSink} instances
+ *
+ * @param <U> The type of the state element
+ */
+ private static abstract class Box<U> {
+ 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 <T> the output type of the stream pipeline
+ * @param <R> the result type of the reducing operation
+ * @param <S> the type of the {@code AccumulatingSink}
+ */
+ private static abstract class ReduceOp<T, R, S extends AccumulatingSink<T, R, S>>
+ implements TerminalOp<T, R> {
+ 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 <P_IN> R evaluateSequential(PipelineHelper<T> helper,
+ Spliterator<P_IN> spliterator) {
+ return helper.wrapAndCopyInto(makeSink(), spliterator).get();
+ }
+
+ @Override
+ public <P_IN> R evaluateParallel(PipelineHelper<T> helper,
+ Spliterator<P_IN> 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<P_IN, P_OUT, R,
+ S extends AccumulatingSink<P_OUT, R, S>>
+ extends AbstractTask<P_IN, P_OUT, S, ReduceTask<P_IN, P_OUT, R, S>> {
+ private final ReduceOp<P_OUT, R, S> op;
+
+ ReduceTask(ReduceOp<P_OUT, R, S> op,
+ PipelineHelper<P_OUT> helper,
+ Spliterator<P_IN> spliterator) {
+ super(helper, spliterator);
+ this.op = op;
+ }
+
+ ReduceTask(ReduceTask<P_IN, P_OUT, R, S> parent,
+ Spliterator<P_IN> spliterator) {
+ super(parent, spliterator);
+ this.op = parent.op;
+ }
+
+ @Override
+ protected ReduceTask<P_IN, P_OUT, R, S> makeChild(Spliterator<P_IN> 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);
+ }
+ }
+}