8164691: Stream specification clarifications for iterate and collect
Reviewed-by: briangoetz, smarks, tvaleev
--- a/jdk/src/java.base/share/classes/java/util/stream/DoubleStream.java Fri Sep 09 14:54:24 2016 -0700
+++ b/jdk/src/java.base/share/classes/java/util/stream/DoubleStream.java Fri Sep 09 14:54:29 2016 -0700
@@ -567,19 +567,23 @@
* <p>This is a <a href="package-summary.html#StreamOps">terminal
* operation</a>.
*
- * @param <R> type of the result
- * @param supplier a function that creates a new result container. For a
- * parallel execution, this function may be called
+ * @param <R> the type of the mutable result container
+ * @param supplier a function that creates a new mutable result container.
+ * For a parallel execution, this function may be called
* multiple times and must return a fresh value each time.
* @param accumulator an <a href="package-summary.html#Associativity">associative</a>,
* <a href="package-summary.html#NonInterference">non-interfering</a>,
* <a href="package-summary.html#Statelessness">stateless</a>
- * function for incorporating an additional element into a result
+ * function that must fold an element into a result
+ * container.
* @param combiner an <a href="package-summary.html#Associativity">associative</a>,
* <a href="package-summary.html#NonInterference">non-interfering</a>,
* <a href="package-summary.html#Statelessness">stateless</a>
- * function for combining two values, which must be
- * compatible with the accumulator function
+ * function that accepts two partial result containers
+ * and merges them, which must be compatible with the
+ * accumulator function. The combiner function must fold
+ * the elements from the second result container into the
+ * first result container.
* @return the result of the reduction
* @see Stream#collect(Supplier, BiConsumer, BiConsumer)
*/
@@ -947,6 +951,12 @@
* position {@code n}, will be the result of applying the function {@code f}
* to the element at position {@code n - 1}.
*
+ * <p>The action of applying {@code f} for one element
+ * <a href="../concurrent/package-summary.html#MemoryVisibility"><i>happens-before</i></a>
+ * the action of applying {@code f} for subsequent elements. For any given
+ * element the action may be performed in whatever thread the library
+ * chooses.
+ *
* @param seed the initial element
* @param f a function to be applied to the previous element to produce
* a new element
@@ -978,37 +988,44 @@
/**
* Returns a sequential ordered {@code DoubleStream} produced by iterative
- * application of a function to an initial element, conditioned on
- * satisfying the supplied predicate. The stream terminates as soon as
- * the predicate returns false.
+ * application of the given {@code next} function to an initial element,
+ * conditioned on satisfying the given {@code hasNext} predicate. The
+ * stream terminates as soon as the {@code hasNext} predicate returns false.
*
- * <p>
- * {@code DoubleStream.iterate} should produce the same sequence of
- * elements as produced by the corresponding for-loop:
+ * <p>{@code DoubleStream.iterate} should produce the same sequence of elements as
+ * produced by the corresponding for-loop:
* <pre>{@code
- * for (double index=seed; predicate.test(index); index = f.applyAsDouble(index)) {
+ * for (double index=seed; hasNext.test(index); index = next.applyAsDouble(index)) {
* ...
* }
* }</pre>
*
- * <p>
- * The resulting sequence may be empty if the predicate does not hold on
- * the seed value. Otherwise the first element will be the supplied seed
- * value, the next element (if present) will be the result of applying the
- * function f to the seed value, and so on iteratively until the predicate
- * indicates that the stream should terminate.
+ * <p>The resulting sequence may be empty if the {@code hasNext} predicate
+ * does not hold on the seed value. Otherwise the first element will be the
+ * supplied {@code seed} value, the next element (if present) will be the
+ * result of applying the {@code next} function to the {@code seed} value,
+ * and so on iteratively until the {@code hasNext} predicate indicates that
+ * the stream should terminate.
+ *
+ * <p>The action of applying the {@code hasNext} predicate to an element
+ * <a href="../concurrent/package-summary.html#MemoryVisibility"><i>happens-before</i></a>
+ * the action of applying the {@code next} function to that element. The
+ * action of applying the {@code next} function for one element
+ * <i>happens-before</i> the action of applying the {@code hasNext}
+ * predicate for subsequent elements. For any given element an action may
+ * be performed in whatever thread the library chooses.
*
* @param seed the initial element
- * @param predicate a predicate to apply to elements to determine when the
- * stream must terminate.
- * @param f a function to be applied to the previous element to produce
- * a new element
+ * @param hasNext a predicate to apply to elements to determine when the
+ * stream must terminate.
+ * @param next a function to be applied to the previous element to produce
+ * a new element
* @return a new sequential {@code DoubleStream}
* @since 9
*/
- public static DoubleStream iterate(double seed, DoublePredicate predicate, DoubleUnaryOperator f) {
- Objects.requireNonNull(f);
- Objects.requireNonNull(predicate);
+ public static DoubleStream iterate(double seed, DoublePredicate hasNext, DoubleUnaryOperator next) {
+ Objects.requireNonNull(next);
+ Objects.requireNonNull(hasNext);
Spliterator.OfDouble spliterator = new Spliterators.AbstractDoubleSpliterator(Long.MAX_VALUE,
Spliterator.ORDERED | Spliterator.IMMUTABLE | Spliterator.NONNULL) {
double prev;
@@ -1021,12 +1038,12 @@
return false;
double t;
if (started)
- t = f.applyAsDouble(prev);
+ t = next.applyAsDouble(prev);
else {
t = seed;
started = true;
}
- if (!predicate.test(t)) {
+ if (!hasNext.test(t)) {
finished = true;
return false;
}
@@ -1040,10 +1057,10 @@
if (finished)
return;
finished = true;
- double t = started ? f.applyAsDouble(prev) : seed;
- while (predicate.test(t)) {
+ double t = started ? next.applyAsDouble(prev) : seed;
+ while (hasNext.test(t)) {
action.accept(t);
- t = f.applyAsDouble(t);
+ t = next.applyAsDouble(t);
}
}
};
--- a/jdk/src/java.base/share/classes/java/util/stream/IntStream.java Fri Sep 09 14:54:24 2016 -0700
+++ b/jdk/src/java.base/share/classes/java/util/stream/IntStream.java Fri Sep 09 14:54:29 2016 -0700
@@ -562,19 +562,23 @@
* <p>This is a <a href="package-summary.html#StreamOps">terminal
* operation</a>.
*
- * @param <R> type of the result
- * @param supplier a function that creates a new result container. For a
- * parallel execution, this function may be called
+ * @param <R> the type of the mutable result container
+ * @param supplier a function that creates a new mutable result container.
+ * For a parallel execution, this function may be called
* multiple times and must return a fresh value each time.
* @param accumulator an <a href="package-summary.html#Associativity">associative</a>,
* <a href="package-summary.html#NonInterference">non-interfering</a>,
* <a href="package-summary.html#Statelessness">stateless</a>
- * function for incorporating an additional element into a result
+ * function that must fold an element into a result
+ * container.
* @param combiner an <a href="package-summary.html#Associativity">associative</a>,
* <a href="package-summary.html#NonInterference">non-interfering</a>,
* <a href="package-summary.html#Statelessness">stateless</a>
- * function for combining two values, which must be
- * compatible with the accumulator function
+ * function that accepts two partial result containers
+ * and merges them, which must be compatible with the
+ * accumulator function. The combiner function must fold
+ * the elements from the second result container into the
+ * first result container.
* @return the result of the reduction
* @see Stream#collect(Supplier, BiConsumer, BiConsumer)
*/
@@ -887,6 +891,12 @@
* {@code n}, will be the result of applying the function {@code f} to the
* element at position {@code n - 1}.
*
+ * <p>The action of applying {@code f} for one element
+ * <a href="../concurrent/package-summary.html#MemoryVisibility"><i>happens-before</i></a>
+ * the action of applying {@code f} for subsequent elements. For any given
+ * element the action may be performed in whatever thread the library
+ * chooses.
+ *
* @param seed the initial element
* @param f a function to be applied to the previous element to produce
* a new element
@@ -918,37 +928,44 @@
/**
* Returns a sequential ordered {@code IntStream} produced by iterative
- * application of a function to an initial element, conditioned on
- * satisfying the supplied predicate. The stream terminates as soon as
- * the predicate returns false.
+ * application of the given {@code next} function to an initial element,
+ * conditioned on satisfying the given {@code hasNext} predicate. The
+ * stream terminates as soon as the {@code hasNext} predicate returns false.
*
- * <p>
- * {@code IntStream.iterate} should produce the same sequence of elements
- * as produced by the corresponding for-loop:
+ * <p>{@code IntStream.iterate} should produce the same sequence of elements as
+ * produced by the corresponding for-loop:
* <pre>{@code
- * for (int index=seed; predicate.test(index); index = f.applyAsInt(index)) {
+ * for (int index=seed; hasNext.test(index); index = next.applyAsInt(index)) {
* ...
* }
* }</pre>
*
- * <p>
- * The resulting sequence may be empty if the predicate does not hold on
- * the seed value. Otherwise the first element will be the supplied seed
- * value, the next element (if present) will be the result of applying the
- * function f to the seed value, and so on iteratively until the predicate
- * indicates that the stream should terminate.
+ * <p>The resulting sequence may be empty if the {@code hasNext} predicate
+ * does not hold on the seed value. Otherwise the first element will be the
+ * supplied {@code seed} value, the next element (if present) will be the
+ * result of applying the {@code next} function to the {@code seed} value,
+ * and so on iteratively until the {@code hasNext} predicate indicates that
+ * the stream should terminate.
+ *
+ * <p>The action of applying the {@code hasNext} predicate to an element
+ * <a href="../concurrent/package-summary.html#MemoryVisibility"><i>happens-before</i></a>
+ * the action of applying the {@code next} function to that element. The
+ * action of applying the {@code next} function for one element
+ * <i>happens-before</i> the action of applying the {@code hasNext}
+ * predicate for subsequent elements. For any given element an action may
+ * be performed in whatever thread the library chooses.
*
* @param seed the initial element
- * @param predicate a predicate to apply to elements to determine when the
- * stream must terminate.
- * @param f a function to be applied to the previous element to produce
- * a new element
+ * @param hasNext a predicate to apply to elements to determine when the
+ * stream must terminate.
+ * @param next a function to be applied to the previous element to produce
+ * a new element
* @return a new sequential {@code IntStream}
* @since 9
*/
- public static IntStream iterate(int seed, IntPredicate predicate, IntUnaryOperator f) {
- Objects.requireNonNull(f);
- Objects.requireNonNull(predicate);
+ public static IntStream iterate(int seed, IntPredicate hasNext, IntUnaryOperator next) {
+ Objects.requireNonNull(next);
+ Objects.requireNonNull(hasNext);
Spliterator.OfInt spliterator = new Spliterators.AbstractIntSpliterator(Long.MAX_VALUE,
Spliterator.ORDERED | Spliterator.IMMUTABLE | Spliterator.NONNULL) {
int prev;
@@ -961,12 +978,12 @@
return false;
int t;
if (started)
- t = f.applyAsInt(prev);
+ t = next.applyAsInt(prev);
else {
t = seed;
started = true;
}
- if (!predicate.test(t)) {
+ if (!hasNext.test(t)) {
finished = true;
return false;
}
@@ -980,10 +997,10 @@
if (finished)
return;
finished = true;
- int t = started ? f.applyAsInt(prev) : seed;
- while (predicate.test(t)) {
+ int t = started ? next.applyAsInt(prev) : seed;
+ while (hasNext.test(t)) {
action.accept(t);
- t = f.applyAsInt(t);
+ t = next.applyAsInt(t);
}
}
};
--- a/jdk/src/java.base/share/classes/java/util/stream/LongStream.java Fri Sep 09 14:54:24 2016 -0700
+++ b/jdk/src/java.base/share/classes/java/util/stream/LongStream.java Fri Sep 09 14:54:29 2016 -0700
@@ -564,19 +564,23 @@
* <p>This is a <a href="package-summary.html#StreamOps">terminal
* operation</a>.
*
- * @param <R> type of the result
- * @param supplier a function that creates a new result container. For a
- * parallel execution, this function may be called
+ * @param <R> the type of the mutable result container
+ * @param supplier a function that creates a new mutable result container.
+ * For a parallel execution, this function may be called
* multiple times and must return a fresh value each time.
* @param accumulator an <a href="package-summary.html#Associativity">associative</a>,
* <a href="package-summary.html#NonInterference">non-interfering</a>,
* <a href="package-summary.html#Statelessness">stateless</a>
- * function for incorporating an additional element into a result
+ * function that must fold an element into a result
+ * container.
* @param combiner an <a href="package-summary.html#Associativity">associative</a>,
* <a href="package-summary.html#NonInterference">non-interfering</a>,
* <a href="package-summary.html#Statelessness">stateless</a>
- * function for combining two values, which must be
- * compatible with the accumulator function
+ * function that accepts two partial result containers
+ * and merges them, which must be compatible with the
+ * accumulator function. The combiner function must fold
+ * the elements from the second result container into the
+ * first result container.
* @return the result of the reduction
* @see Stream#collect(Supplier, BiConsumer, BiConsumer)
*/
@@ -877,6 +881,12 @@
* {@code n}, will be the result of applying the function {@code f} to the
* element at position {@code n - 1}.
*
+ * <p>The action of applying {@code f} for one element
+ * <a href="../concurrent/package-summary.html#MemoryVisibility"><i>happens-before</i></a>
+ * the action of applying {@code f} for subsequent elements. For any given
+ * element the action may be performed in whatever thread the library
+ * chooses.
+ *
* @param seed the initial element
* @param f a function to be applied to the previous element to produce
* a new element
@@ -908,37 +918,44 @@
/**
* Returns a sequential ordered {@code LongStream} produced by iterative
- * application of a function to an initial element, conditioned on
- * satisfying the supplied predicate. The stream terminates as soon as
- * the predicate returns false.
+ * application of the given {@code next} function to an initial element,
+ * conditioned on satisfying the given {@code hasNext} predicate. The
+ * stream terminates as soon as the {@code hasNext} predicate returns false.
*
- * <p>
- * {@code LongStream.iterate} should produce the same sequence of elements
- * as produced by the corresponding for-loop:
+ * <p>{@code LongStream.iterate} should produce the same sequence of elements as
+ * produced by the corresponding for-loop:
* <pre>{@code
- * for (long index=seed; predicate.test(index); index = f.applyAsLong(index)) {
+ * for (long index=seed; hasNext.test(index); index = next.applyAsLong(index)) {
* ...
* }
* }</pre>
*
- * <p>
- * The resulting sequence may be empty if the predicate does not hold on
- * the seed value. Otherwise the first element will be the supplied seed
- * value, the next element (if present) will be the result of applying the
- * function f to the seed value, and so on iteratively until the predicate
- * indicates that the stream should terminate.
+ * <p>The resulting sequence may be empty if the {@code hasNext} predicate
+ * does not hold on the seed value. Otherwise the first element will be the
+ * supplied {@code seed} value, the next element (if present) will be the
+ * result of applying the {@code next} function to the {@code seed} value,
+ * and so on iteratively until the {@code hasNext} predicate indicates that
+ * the stream should terminate.
+ *
+ * <p>The action of applying the {@code hasNext} predicate to an element
+ * <a href="../concurrent/package-summary.html#MemoryVisibility"><i>happens-before</i></a>
+ * the action of applying the {@code next} function to that element. The
+ * action of applying the {@code next} function for one element
+ * <i>happens-before</i> the action of applying the {@code hasNext}
+ * predicate for subsequent elements. For any given element an action may
+ * be performed in whatever thread the library chooses.
*
* @param seed the initial element
- * @param predicate a predicate to apply to elements to determine when the
- * stream must terminate.
- * @param f a function to be applied to the previous element to produce
- * a new element
+ * @param hasNext a predicate to apply to elements to determine when the
+ * stream must terminate.
+ * @param next a function to be applied to the previous element to produce
+ * a new element
* @return a new sequential {@code LongStream}
* @since 9
*/
- public static LongStream iterate(long seed, LongPredicate predicate, LongUnaryOperator f) {
- Objects.requireNonNull(f);
- Objects.requireNonNull(predicate);
+ public static LongStream iterate(long seed, LongPredicate hasNext, LongUnaryOperator next) {
+ Objects.requireNonNull(next);
+ Objects.requireNonNull(hasNext);
Spliterator.OfLong spliterator = new Spliterators.AbstractLongSpliterator(Long.MAX_VALUE,
Spliterator.ORDERED | Spliterator.IMMUTABLE | Spliterator.NONNULL) {
long prev;
@@ -951,12 +968,12 @@
return false;
long t;
if (started)
- t = f.applyAsLong(prev);
+ t = next.applyAsLong(prev);
else {
t = seed;
started = true;
}
- if (!predicate.test(t)) {
+ if (!hasNext.test(t)) {
finished = true;
return false;
}
@@ -970,10 +987,10 @@
if (finished)
return;
finished = true;
- long t = started ? f.applyAsLong(prev) : seed;
- while (predicate.test(t)) {
+ long t = started ? next.applyAsLong(prev) : seed;
+ while (hasNext.test(t)) {
action.accept(t);
- t = f.applyAsLong(t);
+ t = next.applyAsLong(t);
}
}
};
--- a/jdk/src/java.base/share/classes/java/util/stream/Stream.java Fri Sep 09 14:54:24 2016 -0700
+++ b/jdk/src/java.base/share/classes/java/util/stream/Stream.java Fri Sep 09 14:54:29 2016 -0700
@@ -882,19 +882,23 @@
* .toString();
* }</pre>
*
- * @param <R> type of the result
- * @param supplier a function that creates a new result container. For a
- * parallel execution, this function may be called
+ * @param <R> the type of the mutable result container
+ * @param supplier a function that creates a new mutable result container.
+ * For a parallel execution, this function may be called
* multiple times and must return a fresh value each time.
* @param accumulator an <a href="package-summary.html#Associativity">associative</a>,
* <a href="package-summary.html#NonInterference">non-interfering</a>,
* <a href="package-summary.html#Statelessness">stateless</a>
- * function for incorporating an additional element into a result
+ * function that must fold an element into a result
+ * container.
* @param combiner an <a href="package-summary.html#Associativity">associative</a>,
* <a href="package-summary.html#NonInterference">non-interfering</a>,
* <a href="package-summary.html#Statelessness">stateless</a>
- * function for combining two values, which must be
- * compatible with the accumulator function
+ * function that accepts two partial result containers
+ * and merges them, which must be compatible with the
+ * accumulator function. The combiner function must fold
+ * the elements from the second result container into the
+ * first result container.
* @return the result of the reduction
*/
<R> R collect(Supplier<R> supplier,
@@ -1194,6 +1198,12 @@
* {@code n}, will be the result of applying the function {@code f} to the
* element at position {@code n - 1}.
*
+ * <p>The action of applying {@code f} for one element
+ * <a href="../concurrent/package-summary.html#MemoryVisibility"><i>happens-before</i></a>
+ * the action of applying {@code f} for subsequent elements. For any given
+ * element the action may be performed in whatever thread the library
+ * chooses.
+ *
* @param <T> the type of stream elements
* @param seed the initial element
* @param f a function to be applied to the previous element to produce
@@ -1226,38 +1236,45 @@
/**
* Returns a sequential ordered {@code Stream} produced by iterative
- * application of a function to an initial element, conditioned on
- * satisfying the supplied predicate. The stream terminates as soon as
- * the predicate returns false.
+ * application of the given {@code next} function to an initial element,
+ * conditioned on satisfying the given {@code hasNext} predicate. The
+ * stream terminates as soon as the {@code hasNext} predicate returns false.
*
- * <p>
- * {@code Stream.iterate} should produce the same sequence of elements as
+ * <p>{@code Stream.iterate} should produce the same sequence of elements as
* produced by the corresponding for-loop:
* <pre>{@code
- * for (T index=seed; predicate.test(index); index = f.apply(index)) {
+ * for (T index=seed; hasNext.test(index); index = next.apply(index)) {
* ...
* }
* }</pre>
*
- * <p>
- * The resulting sequence may be empty if the predicate does not hold on
- * the seed value. Otherwise the first element will be the supplied seed
- * value, the next element (if present) will be the result of applying the
- * function f to the seed value, and so on iteratively until the predicate
- * indicates that the stream should terminate.
+ * <p>The resulting sequence may be empty if the {@code hasNext} predicate
+ * does not hold on the seed value. Otherwise the first element will be the
+ * supplied {@code seed} value, the next element (if present) will be the
+ * result of applying the {@code next} function to the {@code seed} value,
+ * and so on iteratively until the {@code hasNext} predicate indicates that
+ * the stream should terminate.
+ *
+ * <p>The action of applying the {@code hasNext} predicate to an element
+ * <a href="../concurrent/package-summary.html#MemoryVisibility"><i>happens-before</i></a>
+ * the action of applying the {@code next} function to that element. The
+ * action of applying the {@code next} function for one element
+ * <i>happens-before</i> the action of applying the {@code hasNext}
+ * predicate for subsequent elements. For any given element an action may
+ * be performed in whatever thread the library chooses.
*
* @param <T> the type of stream elements
* @param seed the initial element
- * @param predicate a predicate to apply to elements to determine when the
- * stream must terminate.
- * @param f a function to be applied to the previous element to produce
- * a new element
+ * @param hasNext a predicate to apply to elements to determine when the
+ * stream must terminate.
+ * @param next a function to be applied to the previous element to produce
+ * a new element
* @return a new sequential {@code Stream}
* @since 9
*/
- public static<T> Stream<T> iterate(T seed, Predicate<? super T> predicate, UnaryOperator<T> f) {
- Objects.requireNonNull(f);
- Objects.requireNonNull(predicate);
+ public static<T> Stream<T> iterate(T seed, Predicate<? super T> hasNext, UnaryOperator<T> next) {
+ Objects.requireNonNull(next);
+ Objects.requireNonNull(hasNext);
Spliterator<T> spliterator = new Spliterators.AbstractSpliterator<>(Long.MAX_VALUE,
Spliterator.ORDERED | Spliterator.IMMUTABLE) {
T prev;
@@ -1270,12 +1287,12 @@
return false;
T t;
if (started)
- t = f.apply(prev);
+ t = next.apply(prev);
else {
t = seed;
started = true;
}
- if (!predicate.test(t)) {
+ if (!hasNext.test(t)) {
prev = null;
finished = true;
return false;
@@ -1290,11 +1307,11 @@
if (finished)
return;
finished = true;
- T t = started ? f.apply(prev) : seed;
+ T t = started ? next.apply(prev) : seed;
prev = null;
- while (predicate.test(t)) {
+ while (hasNext.test(t)) {
action.accept(t);
- t = f.apply(t);
+ t = next.apply(t);
}
}
};