File: Collections.drv

package info (click to toggle)
libfastutil-java 8.5.15%2Bdfsg-1
  • links: PTS, VCS
  • area: main
  • in suites: forky, sid, trixie
  • size: 4,076 kB
  • sloc: java: 19,670; sh: 1,188; makefile: 473; xml: 354
file content (624 lines) | stat: -rw-r--r-- 22,266 bytes parent folder | download
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
/*
 * Copyright (C) 2002-2024 Sebastiano Vigna
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */


package PACKAGE;

import java.util.Collection;
import java.util.Objects;
import java.util.function.Consumer;

#if KEYS_BYTE_CHAR_SHORT_FLOAT
import WIDENED_PACKAGE.KEY_WIDENED_ITERATOR;
import WIDENED_PACKAGE.WIDENED_ITERATORS;
import WIDENED_PACKAGE.KEY_WIDENED_SPLITERATOR;
import WIDENED_PACKAGE.WIDENED_SPLITERATORS;
#elif ! KEY_CLASS_Boolean
import java.util.concurrent.atomic.AtomicInteger;
import java.util.function.IntFunction;
import java.util.function.Supplier;
#endif

#if ! KEYS_REFERENCE
import it.unimi.dsi.fastutil.objects.ObjectArrays;
#else
import java.util.function.Predicate;
#endif

/** A class providing static methods and objects that do useful things with type-specific collections.
 *
 * @see java.util.Collections
 */

public final class COLLECTIONS {

	private COLLECTIONS() {}

#if KEYS_PRIMITIVE && !KEY_TYPE_Boolean
	/* Only in the EmptyCollection class, where performance is critical, do we override the
	 * deprecated, Object based functional methods. For the rest, we just override the
	 * non-deprecated type-specific method, and let the default method from the interface
	 * filter into that. This is an extra method call and lambda creation, but it isn't worth
	 * complexifying the code generation for a case that is already marked as being inefficient.
	 */
#endif

	/** An immutable class representing an empty type-specific collection.
	 *
	 * <p>This class may be useful to implement your own in case you subclass
	 * a type-specific collection.
	 */

	public abstract static class EmptyCollection KEY_GENERIC extends ABSTRACT_COLLECTION KEY_GENERIC {
		protected EmptyCollection() {}

		@Override
		public boolean contains(KEY_TYPE k) { return false; }

		@Override
		public Object[] toArray() { return ObjectArrays.EMPTY_ARRAY; }

		@Override
		public <T> T[] toArray(T[] array) {
			if (array.length > 0) array[0] = null;
			return array;
		}

		@Override
		SUPPRESS_WARNINGS_KEY_UNCHECKED
		public KEY_BIDI_ITERATOR KEY_GENERIC iterator() { return ITERATORS.EMPTY_ITERATOR; }

		@Override
		SUPPRESS_WARNINGS_KEY_UNCHECKED
		public KEY_SPLITERATOR KEY_GENERIC spliterator() { return SPLITERATORS.EMPTY_SPLITERATOR; }

		@Override
		public int size() { return 0; }

		@Override
		public void clear() {}

		@Override
		public int hashCode() { return 0; }

		@Override
		public boolean equals(Object o) {
			if (o == this) return true;
			if (! (o instanceof Collection)) return false;
			return ((Collection<?>)o).isEmpty();
		}

		DEPRECATED_IF_KEYS_PRIMITIVE
		@Override
		public void forEach(final Consumer<? super KEY_GENERIC_CLASS> action) { }

		@Override
		public boolean containsAll(final Collection<?> c) { return c.isEmpty(); }

		@Override
		public boolean addAll(final Collection<? extends KEY_GENERIC_CLASS> c) { throw new UnsupportedOperationException(); }

		@Override
		public boolean removeAll(final Collection<?> c) { throw new UnsupportedOperationException(); }

		@Override
		public boolean retainAll(final Collection<?> c) { throw new UnsupportedOperationException(); }

#if KEYS_PRIMITIVE
		@Deprecated
#endif
		@Override
		public boolean removeIf(final java.util.function.Predicate<? super KEY_GENERIC_CLASS> filter) {
			Objects.requireNonNull(filter);
			return false;
		}
#if KEYS_PRIMITIVE

		@Override
		public KEY_TYPE[] TO_KEY_ARRAY() { return ARRAYS.EMPTY_ARRAY; }

		/* {@inheritDoc}
		 * @deprecated Please use {@code toArray()} instead&mdash;this method is redundant and will be removed in the future.
		 */
		@Deprecated
		@Override
		public KEY_TYPE[] TO_KEY_ARRAY(KEY_TYPE[] a) { return a; }

		@Override
		public void forEach(final METHOD_ARG_KEY_CONSUMER action) { }

		@Override
		public boolean containsAll(final COLLECTION c) { return c.isEmpty(); }

		@Override
		public boolean addAll(final COLLECTION c) { throw new UnsupportedOperationException(); }

		@Override
		public boolean removeAll(final COLLECTION c) { throw new UnsupportedOperationException(); }

		@Override
		public boolean retainAll(final COLLECTION c) { throw new UnsupportedOperationException(); }

		@Override
		public boolean removeIf(final METHOD_ARG_PREDICATE filter) {
			Objects.requireNonNull(filter);
			return false;
		}

#if KEYS_BYTE_CHAR_SHORT_FLOAT
		@Override
		public KEY_WIDENED_ITERATOR KEY_WIDENED_ITERATOR_METHOD() { return WIDENED_ITERATORS.EMPTY_ITERATOR; }

		@Override
		public KEY_WIDENED_SPLITERATOR KEY_WIDENED_SPLITERATOR_METHOD() { return WIDENED_SPLITERATORS.EMPTY_SPLITERATOR; }
#endif

#endif

	}


	/** A synchronized wrapper class for collections. */

	static class SynchronizedCollection KEY_GENERIC implements COLLECTION KEY_GENERIC, java.io.Serializable {

		private static final long serialVersionUID = -7046029254386353129L;

		protected final COLLECTION KEY_GENERIC collection;
		protected final Object sync;

		protected SynchronizedCollection(final COLLECTION KEY_GENERIC c, final Object sync) {
			this.collection = Objects.requireNonNull(c);
			this.sync = sync;
		}

		protected SynchronizedCollection(final COLLECTION KEY_GENERIC c) {
			this.collection = Objects.requireNonNull(c);
			this.sync = this;
		}

		@Override
		public boolean add(final KEY_GENERIC_TYPE k) { synchronized(sync) { return collection.add(k); } }

		@Override
		public boolean contains(final KEY_TYPE k) { synchronized(sync) { return collection.contains(k); } }

		@Override
		public boolean REMOVE(final KEY_TYPE k) { synchronized(sync) { return collection.REMOVE(k); } }

		@Override
		public int size() { synchronized(sync) { return collection.size(); } }

		@Override
		public boolean isEmpty() { synchronized(sync) { return collection.isEmpty(); } }

		@Override
		public KEY_TYPE[] TO_KEY_ARRAY() { synchronized(sync) { return collection.TO_KEY_ARRAY(); } }

#if KEYS_PRIMITIVE
		@Override
		public Object[] toArray() { synchronized(sync) { return collection.toArray(); } }

		/* {@inheritDoc}
		 * @deprecated Please use {@code toArray()} instead&mdash;this method is redundant and will be removed in the future.
		 */
		@Deprecated
		@Override
		public KEY_TYPE[] TO_KEY_ARRAY(final KEY_TYPE[] a) { return toArray(a); }

		@Override
		public KEY_TYPE[] toArray(final KEY_TYPE[] a) { synchronized(sync) { return collection.toArray(a); } }

		@Override
		public boolean addAll(final COLLECTION c) { synchronized(sync) { return collection.addAll(c); } }

		@Override
		public boolean containsAll(final COLLECTION c) { synchronized(sync) { return collection.containsAll(c); } }

		@Override
		public boolean removeAll(final COLLECTION c) { synchronized(sync) { return collection.removeAll(c); } }

		@Override
		public boolean retainAll(final COLLECTION c) { synchronized(sync) { return collection.retainAll(c); } }

		@Override
		@Deprecated
		public boolean add(final KEY_GENERIC_CLASS k) { synchronized(sync) { return collection.add(k); } }

		@Override
		@Deprecated
		public boolean contains(final Object k) { synchronized(sync) { return collection.contains(k); } }

		@Override
		@Deprecated
		public boolean remove(final Object k) { synchronized(sync) { return collection.remove(k); } }

#if defined JDK_PRIMITIVE_ITERATOR
		@Override
		public KEY_WIDENED_ITERATOR KEY_WIDENED_ITERATOR_METHOD() { return collection.KEY_WIDENED_ITERATOR_METHOD(); }

		@Override
		public KEY_WIDENED_SPLITERATOR KEY_WIDENED_SPLITERATOR_METHOD() { return collection.KEY_WIDENED_SPLITERATOR_METHOD(); }
#endif

#if defined JDK_PRIMITIVE_STREAM
		@Override
		public JDK_PRIMITIVE_STREAM KEY_WIDENED_STREAM_METHOD() { return collection.KEY_WIDENED_STREAM_METHOD(); }

		@Override
		public JDK_PRIMITIVE_STREAM KEY_WIDENED_PARALLEL_STREAM_METHOD() { return collection.KEY_WIDENED_PARALLEL_STREAM_METHOD(); }
#endif
#endif

		@Override
		public <T> T[] toArray(final T[] a) { synchronized(sync) { return collection.toArray(a); } }

		@Override
		public KEY_ITERATOR KEY_GENERIC iterator() { return collection.iterator(); }

		@Override
		public KEY_SPLITERATOR KEY_GENERIC spliterator() { return collection.spliterator(); }

#if defined JDK_PRIMITIVE_STREAM
		@Deprecated
#endif
		@Override
		public java.util.stream.Stream <KEY_GENERIC_CLASS> stream() { return collection.stream(); }

#if defined JDK_PRIMITIVE_STREAM
		@Deprecated
#endif
		@Override
		public java.util.stream.Stream <KEY_GENERIC_CLASS> parallelStream() { return collection.parallelStream(); }

		@Override
		public void forEach(final METHOD_ARG_KEY_CONSUMER action) { synchronized(sync) { collection.forEach(action); } }

		@Override
		public boolean addAll(final Collection<? extends KEY_GENERIC_CLASS> c) { synchronized(sync) { return collection.addAll(c); } }

		@Override
		public boolean containsAll(final Collection<?> c) { synchronized(sync) { return collection.containsAll(c); } }

		@Override
		public boolean removeAll(final Collection<?> c) { synchronized(sync) { return collection.removeAll(c); } }

		@Override
		public boolean retainAll(final Collection<?> c) { synchronized(sync) { return collection.retainAll(c); } }

		@Override
		public boolean removeIf(final METHOD_ARG_PREDICATE filter) { synchronized(sync) { return collection.removeIf(filter); } }

		@Override
		public void clear() { synchronized(sync) { collection.clear(); } }

		@Override
		public String toString() { synchronized(sync) { return collection.toString(); } }

		@Override
		public int hashCode() { synchronized(sync) { return collection.hashCode(); } }

		@Override
		public boolean equals(final Object o) { if (o == this) return true; synchronized(sync) { return collection.equals(o); } }

		private void writeObject(java.io.ObjectOutputStream s) throws java.io.IOException {
			synchronized(sync) { s.defaultWriteObject(); }
		}
	}


	/** Returns a synchronized collection backed by the specified collection.
	 *
	 * @param c the collection to be wrapped in a synchronized collection.
	 * @return a synchronized view of the specified collection.
	 * @see java.util.Collections#synchronizedCollection(Collection)
	 */
	public static KEY_GENERIC COLLECTION KEY_GENERIC synchronize(final COLLECTION KEY_GENERIC c) { return new SynchronizedCollection KEY_GENERIC_DIAMOND(c); }

	/** Returns a synchronized collection backed by the specified collection, using an assigned object to synchronize.
	 *
	 * @param c the collection to be wrapped in a synchronized collection.
	 * @param sync an object that will be used to synchronize the list access.
	 * @return a synchronized view of the specified collection.
	 * @see java.util.Collections#synchronizedCollection(Collection)
	 */

	public static KEY_GENERIC COLLECTION KEY_GENERIC synchronize(final COLLECTION KEY_GENERIC c, final Object sync) { return new SynchronizedCollection KEY_GENERIC_DIAMOND(c, sync); }


	/** An unmodifiable wrapper class for collections. */

	static class UnmodifiableCollection KEY_GENERIC implements COLLECTION KEY_GENERIC, java.io.Serializable {

		private static final long serialVersionUID = -7046029254386353129L;

		protected final COLLECTION KEY_EXTENDS_GENERIC collection;

		protected UnmodifiableCollection(final COLLECTION KEY_EXTENDS_GENERIC c) {
			this.collection = Objects.requireNonNull(c);
		}

		@Override
		public boolean add(final KEY_GENERIC_TYPE k) { throw new UnsupportedOperationException(); }

		@Override
		public boolean REMOVE(final KEY_TYPE k) { throw new UnsupportedOperationException(); }

		@Override
		public int size() { return collection.size(); }

		@Override
		public boolean isEmpty() { return collection.isEmpty(); }

		@Override
		public boolean contains(final KEY_TYPE o) { return collection.contains(o); }

		@Override
		public KEY_ITERATOR KEY_GENERIC iterator() { return ITERATORS.unmodifiable(collection.iterator()); }

		@Override
#if KEYS_PRIMITIVE
		public KEY_SPLITERATOR KEY_GENERIC spliterator() { return collection.spliterator(); }
#else
		@SuppressWarnings("unchecked")
		public KEY_SPLITERATOR KEY_GENERIC spliterator() { return (KEY_SPLITERATOR KEY_GENERIC)collection.spliterator(); }
#endif

#if defined JDK_PRIMITIVE_STREAM
		@Deprecated
#endif
		@Override
#if KEYS_PRIMITIVE
		public java.util.stream.Stream <KEY_GENERIC_CLASS> stream() { return collection.stream(); }
#else
		@SuppressWarnings("unchecked")
		public java.util.stream.Stream <KEY_GENERIC_CLASS> stream() { return (java.util.stream.Stream <KEY_GENERIC_CLASS>)collection.stream(); }
#endif

#if defined JDK_PRIMITIVE_STREAM
		@Deprecated
#endif
		@Override
#if KEYS_PRIMITIVE
		public java.util.stream.Stream <KEY_GENERIC_CLASS> parallelStream() { return collection.parallelStream(); }
#else
		@SuppressWarnings("unchecked")
		public java.util.stream.Stream <KEY_GENERIC_CLASS> parallelStream() { return (java.util.stream.Stream <KEY_GENERIC_CLASS>)collection.parallelStream(); }
#endif

		@Override
		public void clear() { throw new UnsupportedOperationException(); }

		@Override
		public <T> T[] toArray(final T[] a) { return collection.toArray(a); }

		@Override
		public Object[] toArray() { return collection.toArray(); }

		@Override
		public void forEach(final METHOD_ARG_KEY_CONSUMER action) { collection.forEach(action); }

		@Override
		public boolean containsAll(Collection<?> c) { return collection.containsAll(c); }

		@Override
		public boolean addAll(Collection<? extends KEY_GENERIC_CLASS> c) { throw new UnsupportedOperationException(); }

		@Override
		public boolean removeAll(Collection<?> c) { throw new UnsupportedOperationException(); }

		@Override
		public boolean retainAll(Collection<?> c) { throw new UnsupportedOperationException(); }

		@Override
		public boolean removeIf(final METHOD_ARG_PREDICATE filter) { throw new UnsupportedOperationException(); }

#if KEYS_PRIMITIVE
		@Override
		@Deprecated
		public boolean add(final KEY_GENERIC_CLASS k) { throw new UnsupportedOperationException(); }

		@Override
		@Deprecated
		public boolean contains(final Object k) { return collection.contains(k); }

		@Override
		@Deprecated
		public boolean remove(final Object k) { throw new UnsupportedOperationException(); }

		@Override
		public KEY_TYPE[] TO_KEY_ARRAY() { return collection.TO_KEY_ARRAY(); }

		/* {@inheritDoc}
		 * @deprecated Please use {@code toArray()} instead&mdash;this method is redundant.
		 */
		@Deprecated
		@Override
		public KEY_TYPE[] TO_KEY_ARRAY(final KEY_TYPE[] a) { return toArray(a); }

		@Override
		public KEY_TYPE[] toArray(final KEY_TYPE[] a) { return collection.toArray(a); }

		@Override
		public boolean containsAll(COLLECTION c) { return collection.containsAll(c); }

		@Override
		public boolean addAll(COLLECTION c) { throw new UnsupportedOperationException(); }

		@Override
		public boolean removeAll(COLLECTION c) { throw new UnsupportedOperationException(); }

		@Override
		public boolean retainAll(COLLECTION c) { throw new UnsupportedOperationException(); }

#if defined JDK_PRIMITIVE_ITERATOR
		@Override
		public KEY_WIDENED_ITERATOR KEY_WIDENED_ITERATOR_METHOD() { return collection.KEY_WIDENED_ITERATOR_METHOD(); }

		@Override
		public KEY_WIDENED_SPLITERATOR KEY_WIDENED_SPLITERATOR_METHOD() { return collection.KEY_WIDENED_SPLITERATOR_METHOD(); }
#endif

#if defined JDK_PRIMITIVE_STREAM
		@Override
		public JDK_PRIMITIVE_STREAM KEY_WIDENED_STREAM_METHOD() { return collection.KEY_WIDENED_STREAM_METHOD(); }

		@Override
		public JDK_PRIMITIVE_STREAM KEY_WIDENED_PARALLEL_STREAM_METHOD() { return collection.KEY_WIDENED_PARALLEL_STREAM_METHOD(); }
#endif
#endif

		@Override
		public String toString() { return collection.toString(); }

		@Override
		public int hashCode() { return collection.hashCode(); }

		@Override
		public boolean equals(final Object o) { if (o == this) return true; return collection.equals(o); }
	}


	/** Returns an unmodifiable collection backed by the specified collection.
	 *
	 * @param c the collection to be wrapped in an unmodifiable collection.
	 * @return an unmodifiable view of the specified collection.
	 * @see java.util.Collections#unmodifiableCollection(Collection)
	 */
	public static KEY_GENERIC COLLECTION KEY_GENERIC unmodifiable(final COLLECTION KEY_EXTENDS_GENERIC c) { return new UnmodifiableCollection KEY_GENERIC_DIAMOND(c); }

	/** A collection wrapper class for iterables. */

	public static class IterableCollection KEY_GENERIC extends ABSTRACT_COLLECTION KEY_GENERIC implements java.io.Serializable {

		private static final long serialVersionUID = -7046029254386353129L;

		protected final KEY_ITERABLE KEY_GENERIC iterable;

		protected IterableCollection(final KEY_ITERABLE KEY_GENERIC iterable) {
			this.iterable = Objects.requireNonNull(iterable);
		}

		@Override
		public int size() {
			long size = iterable.spliterator().getExactSizeIfKnown();
			if (size >= 0) return (int)Math.min(Integer.MAX_VALUE, size);
			int c = 0;
			final KEY_ITERATOR KEY_GENERIC iterator = iterator();
			while(iterator.hasNext()) {
				iterator.NEXT_KEY();
				c++;
			}

			return c;
		}

		@Override
		public boolean isEmpty() { return ! iterable.iterator().hasNext(); }

		@Override
		public KEY_ITERATOR KEY_GENERIC iterator() { return iterable.iterator(); }

		@Override
		public KEY_SPLITERATOR KEY_GENERIC spliterator() { return iterable.spliterator(); }

#if defined JDK_PRIMITIVE_ITERATOR && KEYS_PRIMITIVE
		@Override
		public KEY_WIDENED_ITERATOR KEY_WIDENED_ITERATOR_METHOD() { return iterable.KEY_WIDENED_ITERATOR_METHOD() ; }

		@Override
		public KEY_WIDENED_SPLITERATOR KEY_WIDENED_SPLITERATOR_METHOD() { return iterable.KEY_WIDENED_SPLITERATOR_METHOD() ; }
#endif
	}


	/** Returns an unmodifiable collection backed by the specified iterable.
	 *
	 * @param iterable the iterable object to be wrapped in an unmodifiable collection.
	 * @return an unmodifiable collection view of the specified iterable.
	 */
	public static KEY_GENERIC COLLECTION KEY_GENERIC asCollection(final KEY_ITERABLE KEY_GENERIC iterable) {
		if (iterable instanceof COLLECTION) return (COLLECTION KEY_GENERIC)iterable;
		// TODO test for Collection but not our collection, and make a wrapper for it.
		return new IterableCollection KEY_GENERIC_DIAMOND(iterable);
	}

#if KEYS_INT_LONG_DOUBLE || KEYS_REFERENCE  // Currently used for the collector methods, which only exist for the "first-class" primitives and object types.
	/** Helper class for size decreasing size estimation.
	 *
	 * <p>Used to implement {@code toXWithExpectedSize} to prevent allocating a data structure big enough for the full stream in every thread, when only one thread
	 * (typically the first one) is going to need to "see" all of it at some point.
	 *
	 * <p>Currently set to always assume a roughly split-by-two strategy from the {@link java.util.Spliterator} backing the
	 * {@link java.util.stream.Stream} (or primitive equivalent). This may perform worse for {@code Spliterator}s that don't
	 * (for example the ones that wrap an {@link java.util.Iterator} as a {@code Spliterator}). This is quite rare in practice however.
	 * But note that even in such cases, this would <em>still</em> perform no worse (modulo some trivial amount) then the default
	 * "flat size for every list" method of combining.
	 * A way to detect such cases and use a different size estimation strategy may come in the future.
	 *
	 * <p>See the {@linkplain #SizeDecreasingSupplier constructor} for requirements of the {@link #builder} functor.
	 */
	static class SizeDecreasingSupplier<
#if KEYS_REFERENCE
			K,
#endif
			C extends COLLECTION KEY_GENERIC> implements Supplier<C> {
		static final int RECOMMENDED_MIN_SIZE = 8;

		final AtomicInteger suppliedCount = new AtomicInteger(0);
		final int expectedFinalSize;
		final IntFunction<C> builder;

		/**
		 * Construct this {@link SizeDecreasingSupplier}.
		 *
		 * @param expectedFinalSize The expected size of the entire remaining contents of the {@code Stream}
		 *   and thus what size the Collection holding the final results should try to be preallocated to.
		 * @param builder the builder function.
		 *   <p>The input integer will be the size of the collection to preallocate.
		 *   <p>It is recommended that you allocate a minimum size if the given {@code size} is small.
		 *     {@link #RECOMMENDED_MIN_SIZE} gives a good enough ballpark for most cases.
		 *   <p>The subclass is free to use the default constructor for the Collection construction
		 *     instead of the {@code size} given
		 *     if {@code size} falls below the default size used for the default initial capacity for
		 *     that Collection implementation. Often such default constructors contain additional
		 *     optimizations that giving an explicit initial capacity would not do (even if given
		 *     the default capacity as the initial capacity explicitly).
		 *   <p>{@link Supplier#get() get()} of the {@link IntFunction} must return non-{@code null}.
		 */
		SizeDecreasingSupplier(int expectedFinalSize, IntFunction<C> builder) {
			this.expectedFinalSize = expectedFinalSize;
			this.builder = builder;
		}

		// This method may be worth pulling into a shared superclass.
		@Override
		public C get() {
			// The "correct" splitting (assuming split by two) would be
			// expectedFinalSize / floor(ln_2(++suppliedCount)). But that seems too much trouble to be worth it.
			// Instead we will take a simple harmonically decreasing ratio (1, 1/2, 1/3, 1/4)
			//
			// Round up int math (to round up, not down) adapted from https://stackoverflow.com/a/503201.
			int expectedNeededNextSize = 1 + ((expectedFinalSize - 1) / suppliedCount.incrementAndGet());
			if (expectedNeededNextSize < 0) {
				// Overflow (and weird below zero results) failsafe
				expectedNeededNextSize = RECOMMENDED_MIN_SIZE;
			}
			return builder.apply(expectedNeededNextSize);
		}
	}
#endif  // KEYS_INT_LONG_DOUBLE || KEYS_REFERENCE
}