archive/jdk
1
0
Fork 0
mirror of https://github.com/openjdk/jdk.git synced 2025-08-28 15:24:43 +02:00
Code Issues Projects Releases Packages Wiki Activity Actions

8072727: add variation of Stream.iterate() that's finite

Browse source 
Reviewed-by: psandoz, briangoetz
This commit is contained in:
Tagir F. Valeev 2016-03-03 10:06:16 +01:00
parent 2255be0267
commit 90adb4174f
10 changed files with 462 additions and 53 deletions
Download patch file Download diff file Expand all files Collapse all files

100
jdk/src/java.base/share/classes/java/util/stream/IntStream.java
View file

@ -1,5 +1,5 @@
/*
* Copyright (c) 2012, 2015, Oracle and/or its affiliates. All rights reserved.
* Copyright (c) 2012, 2016, 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
@ -885,28 +885,104 @@ public interface IntStream extends BaseStream<Integer, IntStream> {
* @param seed the initial element
* @param f a function to be applied to the previous element to produce
* a new element
* @return A new sequential {@code IntStream}
* @return a new sequential {@code IntStream}
*/
public static IntStream iterate(final int seed, final IntUnaryOperator f) {
Objects.requireNonNull(f);
final PrimitiveIterator.OfInt iterator = new PrimitiveIterator.OfInt() {
int t = seed;
Spliterator.OfInt spliterator = new Spliterators.AbstractIntSpliterator(Long.MAX_VALUE,
Spliterator.ORDERED | Spliterator.IMMUTABLE | Spliterator.NONNULL) {
int prev;
boolean started;
@Override
public boolean hasNext() {
public boolean tryAdvance(IntConsumer action) {
Objects.requireNonNull(action);
int t;
if (started)
t = f.applyAsInt(prev);
else {
t = seed;
started = true;
}
action.accept(prev = t);
return true;
}
};
return StreamSupport.intStream(spliterator, false);
}
/**
* 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.
*
* <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.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.
*
* @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
* @return a new sequential {@code IntStream}
* @since 9
*/
public static IntStream iterate(int seed, IntPredicate predicate, IntUnaryOperator f) {
Objects.requireNonNull(f);
Objects.requireNonNull(predicate);
Spliterator.OfInt spliterator = new Spliterators.AbstractIntSpliterator(Long.MAX_VALUE,
Spliterator.ORDERED | Spliterator.IMMUTABLE | Spliterator.NONNULL) {
int prev;
boolean started, finished;
@Override
public boolean tryAdvance(IntConsumer action) {
Objects.requireNonNull(action);
if (finished)
return false;
int t;
if (started)
t = f.applyAsInt(prev);
else {
t = seed;
started = true;
}
if (!predicate.test(t)) {
finished = true;
return false;
}
action.accept(prev = t);
return true;
}
@Override
public int nextInt() {
int v = t;
t = f.applyAsInt(t);
return v;
public void forEachRemaining(IntConsumer action) {
Objects.requireNonNull(action);
if (finished)
return;
finished = true;
int t = started ? f.applyAsInt(prev) : seed;
while (predicate.test(t)) {
action.accept(t);
t = f.applyAsInt(t);
}
}
};
return StreamSupport.intStream(Spliterators.spliteratorUnknownSize(
iterator,
Spliterator.ORDERED | Spliterator.IMMUTABLE | Spliterator.NONNULL), false);
return StreamSupport.intStream(spliterator, false);
}
/**