001/* 002 * Copyright (C) 2017 The Guava Authors 003 * 004 * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except 005 * in compliance with the License. You may obtain a copy of the License at 006 * 007 * http://www.apache.org/licenses/LICENSE-2.0 008 * 009 * Unless required by applicable law or agreed to in writing, software distributed under the License 010 * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express 011 * or implied. See the License for the specific language governing permissions and limitations under 012 * the License. 013 */ 014 015package com.google.common.primitives; 016 017import static com.google.common.base.Preconditions.checkArgument; 018import static com.google.common.base.Preconditions.checkNotNull; 019 020import com.google.common.annotations.GwtCompatible; 021import com.google.common.base.Preconditions; 022import com.google.errorprone.annotations.CanIgnoreReturnValue; 023import com.google.errorprone.annotations.Immutable; 024import java.io.Serializable; 025import java.util.AbstractList; 026import java.util.Arrays; 027import java.util.Collection; 028import java.util.List; 029import java.util.RandomAccess; 030import java.util.Spliterator; 031import java.util.Spliterators; 032import java.util.function.DoubleConsumer; 033import java.util.stream.DoubleStream; 034import javax.annotation.CheckForNull; 035 036/** 037 * An immutable array of {@code double} values, with an API resembling {@link List}. 038 * 039 * <p>Advantages compared to {@code double[]}: 040 * 041 * <ul> 042 * <li>All the many well-known advantages of immutability (read <i>Effective Java</i>, third 043 * edition, Item 17). 044 * <li>Has the value-based (not identity-based) {@link #equals}, {@link #hashCode}, and {@link 045 * #toString} behavior you expect. 046 * <li>Offers useful operations beyond just {@code get} and {@code length}, so you don't have to 047 * hunt through classes like {@link Arrays} and {@link Doubles} for them. 048 * <li>Supports a copy-free {@link #subArray} view, so methods that accept this type don't need to 049 * add overloads that accept start and end indexes. 050 * <li>Can be streamed without "breaking the chain": {@code foo.getBarDoubles().stream()...}. 051 * <li>Access to all collection-based utilities via {@link #asList} (though at the cost of 052 * allocating garbage). 053 * </ul> 054 * 055 * <p>Disadvantages compared to {@code double[]}: 056 * 057 * <ul> 058 * <li>Memory footprint has a fixed overhead (about 24 bytes per instance). 059 * <li><i>Some</i> construction use cases force the data to be copied (though several construction 060 * APIs are offered that don't). 061 * <li>Can't be passed directly to methods that expect {@code double[]} (though the most common 062 * utilities do have replacements here). 063 * <li>Dependency on {@code com.google.common} / Guava. 064 * </ul> 065 * 066 * <p>Advantages compared to {@link com.google.common.collect.ImmutableList ImmutableList}{@code 067 * <Double>}: 068 * 069 * <ul> 070 * <li>Improved memory compactness and locality. 071 * <li>Can be queried without allocating garbage. 072 * <li>Access to {@code DoubleStream} features (like {@link DoubleStream#sum}) using {@code 073 * stream()} instead of the awkward {@code stream().mapToDouble(v -> v)}. 074 * </ul> 075 * 076 * <p>Disadvantages compared to {@code ImmutableList<Double>}: 077 * 078 * <ul> 079 * <li>Can't be passed directly to methods that expect {@code Iterable}, {@code Collection}, or 080 * {@code List} (though the most common utilities do have replacements here, and there is a 081 * lazy {@link #asList} view). 082 * </ul> 083 * 084 * @since 22.0 085 */ 086@GwtCompatible 087@Immutable 088@ElementTypesAreNonnullByDefault 089public final class ImmutableDoubleArray implements Serializable { 090 private static final ImmutableDoubleArray EMPTY = new ImmutableDoubleArray(new double[0]); 091 092 /** Returns the empty array. */ 093 public static ImmutableDoubleArray of() { 094 return EMPTY; 095 } 096 097 /** Returns an immutable array containing a single value. */ 098 public static ImmutableDoubleArray of(double e0) { 099 return new ImmutableDoubleArray(new double[] {e0}); 100 } 101 102 /** Returns an immutable array containing the given values, in order. */ 103 public static ImmutableDoubleArray of(double e0, double e1) { 104 return new ImmutableDoubleArray(new double[] {e0, e1}); 105 } 106 107 /** Returns an immutable array containing the given values, in order. */ 108 public static ImmutableDoubleArray of(double e0, double e1, double e2) { 109 return new ImmutableDoubleArray(new double[] {e0, e1, e2}); 110 } 111 112 /** Returns an immutable array containing the given values, in order. */ 113 public static ImmutableDoubleArray of(double e0, double e1, double e2, double e3) { 114 return new ImmutableDoubleArray(new double[] {e0, e1, e2, e3}); 115 } 116 117 /** Returns an immutable array containing the given values, in order. */ 118 public static ImmutableDoubleArray of(double e0, double e1, double e2, double e3, double e4) { 119 return new ImmutableDoubleArray(new double[] {e0, e1, e2, e3, e4}); 120 } 121 122 /** Returns an immutable array containing the given values, in order. */ 123 public static ImmutableDoubleArray of( 124 double e0, double e1, double e2, double e3, double e4, double e5) { 125 return new ImmutableDoubleArray(new double[] {e0, e1, e2, e3, e4, e5}); 126 } 127 128 // TODO(kevinb): go up to 11? 129 130 /** 131 * Returns an immutable array containing the given values, in order. 132 * 133 * <p>The array {@code rest} must not be longer than {@code Integer.MAX_VALUE - 1}. 134 */ 135 // Use (first, rest) so that `of(someDoubleArray)` won't compile (they should use copyOf), which 136 // is okay since we have to copy the just-created array anyway. 137 public static ImmutableDoubleArray of(double first, double... rest) { 138 checkArgument( 139 rest.length <= Integer.MAX_VALUE - 1, "the total number of elements must fit in an int"); 140 double[] array = new double[rest.length + 1]; 141 array[0] = first; 142 System.arraycopy(rest, 0, array, 1, rest.length); 143 return new ImmutableDoubleArray(array); 144 } 145 146 /** Returns an immutable array containing the given values, in order. */ 147 public static ImmutableDoubleArray copyOf(double[] values) { 148 return values.length == 0 149 ? EMPTY 150 : new ImmutableDoubleArray(Arrays.copyOf(values, values.length)); 151 } 152 153 /** Returns an immutable array containing the given values, in order. */ 154 public static ImmutableDoubleArray copyOf(Collection<Double> values) { 155 return values.isEmpty() ? EMPTY : new ImmutableDoubleArray(Doubles.toArray(values)); 156 } 157 158 /** 159 * Returns an immutable array containing the given values, in order. 160 * 161 * <p><b>Performance note:</b> this method delegates to {@link #copyOf(Collection)} if {@code 162 * values} is a {@link Collection}. Otherwise it creates a {@link #builder} and uses {@link 163 * Builder#addAll(Iterable)}, with all the performance implications associated with that. 164 */ 165 public static ImmutableDoubleArray copyOf(Iterable<Double> values) { 166 if (values instanceof Collection) { 167 return copyOf((Collection<Double>) values); 168 } 169 return builder().addAll(values).build(); 170 } 171 172 /** Returns an immutable array containing all the values from {@code stream}, in order. */ 173 public static ImmutableDoubleArray copyOf(DoubleStream stream) { 174 // Note this uses very different growth behavior from copyOf(Iterable) and the builder. 175 double[] array = stream.toArray(); 176 return (array.length == 0) ? EMPTY : new ImmutableDoubleArray(array); 177 } 178 179 /** 180 * Returns a new, empty builder for {@link ImmutableDoubleArray} instances, sized to hold up to 181 * {@code initialCapacity} values without resizing. The returned builder is not thread-safe. 182 * 183 * <p><b>Performance note:</b> When feasible, {@code initialCapacity} should be the exact number 184 * of values that will be added, if that knowledge is readily available. It is better to guess a 185 * value slightly too high than slightly too low. If the value is not exact, the {@link 186 * ImmutableDoubleArray} that is built will very likely occupy more memory than strictly 187 * necessary; to trim memory usage, build using {@code builder.build().trimmed()}. 188 */ 189 public static Builder builder(int initialCapacity) { 190 checkArgument(initialCapacity >= 0, "Invalid initialCapacity: %s", initialCapacity); 191 return new Builder(initialCapacity); 192 } 193 194 /** 195 * Returns a new, empty builder for {@link ImmutableDoubleArray} instances, with a default initial 196 * capacity. The returned builder is not thread-safe. 197 * 198 * <p><b>Performance note:</b> The {@link ImmutableDoubleArray} that is built will very likely 199 * occupy more memory than necessary; to trim memory usage, build using {@code 200 * builder.build().trimmed()}. 201 */ 202 public static Builder builder() { 203 return new Builder(10); 204 } 205 206 /** 207 * A builder for {@link ImmutableDoubleArray} instances; obtained using {@link 208 * ImmutableDoubleArray#builder}. 209 */ 210 public static final class Builder { 211 private double[] array; 212 private int count = 0; // <= array.length 213 214 Builder(int initialCapacity) { 215 array = new double[initialCapacity]; 216 } 217 218 /** 219 * Appends {@code value} to the end of the values the built {@link ImmutableDoubleArray} will 220 * contain. 221 */ 222 @CanIgnoreReturnValue 223 public Builder add(double value) { 224 ensureRoomFor(1); 225 array[count] = value; 226 count += 1; 227 return this; 228 } 229 230 /** 231 * Appends {@code values}, in order, to the end of the values the built {@link 232 * ImmutableDoubleArray} will contain. 233 */ 234 @CanIgnoreReturnValue 235 public Builder addAll(double[] values) { 236 ensureRoomFor(values.length); 237 System.arraycopy(values, 0, array, count, values.length); 238 count += values.length; 239 return this; 240 } 241 242 /** 243 * Appends {@code values}, in order, to the end of the values the built {@link 244 * ImmutableDoubleArray} will contain. 245 */ 246 @CanIgnoreReturnValue 247 public Builder addAll(Iterable<Double> values) { 248 if (values instanceof Collection) { 249 return addAll((Collection<Double>) values); 250 } 251 for (Double value : values) { 252 add(value); 253 } 254 return this; 255 } 256 257 /** 258 * Appends {@code values}, in order, to the end of the values the built {@link 259 * ImmutableDoubleArray} will contain. 260 */ 261 @CanIgnoreReturnValue 262 public Builder addAll(Collection<Double> values) { 263 ensureRoomFor(values.size()); 264 for (Double value : values) { 265 array[count++] = value; 266 } 267 return this; 268 } 269 270 /** 271 * Appends all values from {@code stream}, in order, to the end of the values the built {@link 272 * ImmutableDoubleArray} will contain. 273 */ 274 @CanIgnoreReturnValue 275 public Builder addAll(DoubleStream stream) { 276 Spliterator.OfDouble spliterator = stream.spliterator(); 277 long size = spliterator.getExactSizeIfKnown(); 278 if (size > 0) { // known *and* nonempty 279 ensureRoomFor(Ints.saturatedCast(size)); 280 } 281 spliterator.forEachRemaining((DoubleConsumer) this::add); 282 return this; 283 } 284 285 /** 286 * Appends {@code values}, in order, to the end of the values the built {@link 287 * ImmutableDoubleArray} will contain. 288 */ 289 @CanIgnoreReturnValue 290 public Builder addAll(ImmutableDoubleArray values) { 291 ensureRoomFor(values.length()); 292 System.arraycopy(values.array, values.start, array, count, values.length()); 293 count += values.length(); 294 return this; 295 } 296 297 private void ensureRoomFor(int numberToAdd) { 298 int newCount = count + numberToAdd; // TODO(kevinb): check overflow now? 299 if (newCount > array.length) { 300 array = Arrays.copyOf(array, expandedCapacity(array.length, newCount)); 301 } 302 } 303 304 // Unfortunately this is pasted from ImmutableCollection.Builder. 305 private static int expandedCapacity(int oldCapacity, int minCapacity) { 306 if (minCapacity < 0) { 307 throw new AssertionError("cannot store more than MAX_VALUE elements"); 308 } 309 // careful of overflow! 310 int newCapacity = oldCapacity + (oldCapacity >> 1) + 1; 311 if (newCapacity < minCapacity) { 312 newCapacity = Integer.highestOneBit(minCapacity - 1) << 1; 313 } 314 if (newCapacity < 0) { 315 newCapacity = Integer.MAX_VALUE; // guaranteed to be >= newCapacity 316 } 317 return newCapacity; 318 } 319 320 /** 321 * Returns a new immutable array. The builder can continue to be used after this call, to append 322 * more values and build again. 323 * 324 * <p><b>Performance note:</b> the returned array is backed by the same array as the builder, so 325 * no data is copied as part of this step, but this may occupy more memory than strictly 326 * necessary. To copy the data to a right-sized backing array, use {@code .build().trimmed()}. 327 */ 328 public ImmutableDoubleArray build() { 329 return count == 0 ? EMPTY : new ImmutableDoubleArray(array, 0, count); 330 } 331 } 332 333 // Instance stuff here 334 335 // The array is never mutated after storing in this field and the construction strategies ensure 336 // it doesn't escape this class 337 @SuppressWarnings("Immutable") 338 private final double[] array; 339 340 /* 341 * TODO(kevinb): evaluate the trade-offs of going bimorphic to save these two fields from most 342 * instances. Note that the instances that would get smaller are the right set to care about 343 * optimizing, because the rest have the option of calling `trimmed`. 344 */ 345 346 private final transient int start; // it happens that we only serialize instances where this is 0 347 private final int end; // exclusive 348 349 private ImmutableDoubleArray(double[] array) { 350 this(array, 0, array.length); 351 } 352 353 private ImmutableDoubleArray(double[] array, int start, int end) { 354 this.array = array; 355 this.start = start; 356 this.end = end; 357 } 358 359 /** Returns the number of values in this array. */ 360 public int length() { 361 return end - start; 362 } 363 364 /** Returns {@code true} if there are no values in this array ({@link #length} is zero). */ 365 public boolean isEmpty() { 366 return end == start; 367 } 368 369 /** 370 * Returns the {@code double} value present at the given index. 371 * 372 * @throws IndexOutOfBoundsException if {@code index} is negative, or greater than or equal to 373 * {@link #length} 374 */ 375 public double get(int index) { 376 Preconditions.checkElementIndex(index, length()); 377 return array[start + index]; 378 } 379 380 /** 381 * Returns the smallest index for which {@link #get} returns {@code target}, or {@code -1} if no 382 * such index exists. Values are compared as if by {@link Double#equals}. Equivalent to {@code 383 * asList().indexOf(target)}. 384 */ 385 public int indexOf(double target) { 386 for (int i = start; i < end; i++) { 387 if (areEqual(array[i], target)) { 388 return i - start; 389 } 390 } 391 return -1; 392 } 393 394 /** 395 * Returns the largest index for which {@link #get} returns {@code target}, or {@code -1} if no 396 * such index exists. Values are compared as if by {@link Double#equals}. Equivalent to {@code 397 * asList().lastIndexOf(target)}. 398 */ 399 public int lastIndexOf(double target) { 400 for (int i = end - 1; i >= start; i--) { 401 if (areEqual(array[i], target)) { 402 return i - start; 403 } 404 } 405 return -1; 406 } 407 408 /** 409 * Returns {@code true} if {@code target} is present at any index in this array. Values are 410 * compared as if by {@link Double#equals}. Equivalent to {@code asList().contains(target)}. 411 */ 412 public boolean contains(double target) { 413 return indexOf(target) >= 0; 414 } 415 416 /** Invokes {@code consumer} for each value contained in this array, in order. */ 417 public void forEach(DoubleConsumer consumer) { 418 checkNotNull(consumer); 419 for (int i = start; i < end; i++) { 420 consumer.accept(array[i]); 421 } 422 } 423 424 /** Returns a stream over the values in this array, in order. */ 425 public DoubleStream stream() { 426 return Arrays.stream(array, start, end); 427 } 428 429 /** Returns a new, mutable copy of this array's values, as a primitive {@code double[]}. */ 430 public double[] toArray() { 431 return Arrays.copyOfRange(array, start, end); 432 } 433 434 /** 435 * Returns a new immutable array containing the values in the specified range. 436 * 437 * <p><b>Performance note:</b> The returned array has the same full memory footprint as this one 438 * does (no actual copying is performed). To reduce memory usage, use {@code subArray(start, 439 * end).trimmed()}. 440 */ 441 public ImmutableDoubleArray subArray(int startIndex, int endIndex) { 442 Preconditions.checkPositionIndexes(startIndex, endIndex, length()); 443 return startIndex == endIndex 444 ? EMPTY 445 : new ImmutableDoubleArray(array, start + startIndex, start + endIndex); 446 } 447 448 private Spliterator.OfDouble spliterator() { 449 return Spliterators.spliterator(array, start, end, Spliterator.IMMUTABLE | Spliterator.ORDERED); 450 } 451 452 /** 453 * Returns an immutable <i>view</i> of this array's values as a {@code List}; note that {@code 454 * double} values are boxed into {@link Double} instances on demand, which can be very expensive. 455 * The returned list should be used once and discarded. For any usages beyond that, pass the 456 * returned list to {@link com.google.common.collect.ImmutableList#copyOf(Collection) 457 * ImmutableList.copyOf} and use that list instead. 458 */ 459 public List<Double> asList() { 460 /* 461 * Typically we cache this kind of thing, but much repeated use of this view is a performance 462 * anti-pattern anyway. If we cache, then everyone pays a price in memory footprint even if 463 * they never use this method. 464 */ 465 return new AsList(this); 466 } 467 468 static class AsList extends AbstractList<Double> implements RandomAccess, Serializable { 469 private final ImmutableDoubleArray parent; 470 471 private AsList(ImmutableDoubleArray parent) { 472 this.parent = parent; 473 } 474 475 // inherit: isEmpty, containsAll, toArray x2, iterator, listIterator, stream, forEach, mutations 476 477 @Override 478 public int size() { 479 return parent.length(); 480 } 481 482 @Override 483 public Double get(int index) { 484 return parent.get(index); 485 } 486 487 @Override 488 public boolean contains(@CheckForNull Object target) { 489 return indexOf(target) >= 0; 490 } 491 492 @Override 493 public int indexOf(@CheckForNull Object target) { 494 return target instanceof Double ? parent.indexOf((Double) target) : -1; 495 } 496 497 @Override 498 public int lastIndexOf(@CheckForNull Object target) { 499 return target instanceof Double ? parent.lastIndexOf((Double) target) : -1; 500 } 501 502 @Override 503 public List<Double> subList(int fromIndex, int toIndex) { 504 return parent.subArray(fromIndex, toIndex).asList(); 505 } 506 507 // The default List spliterator is not efficiently splittable 508 @Override 509 public Spliterator<Double> spliterator() { 510 return parent.spliterator(); 511 } 512 513 @Override 514 public boolean equals(@CheckForNull Object object) { 515 if (object instanceof AsList) { 516 AsList that = (AsList) object; 517 return this.parent.equals(that.parent); 518 } 519 // We could delegate to super now but it would still box too much 520 if (!(object instanceof List)) { 521 return false; 522 } 523 List<?> that = (List<?>) object; 524 if (this.size() != that.size()) { 525 return false; 526 } 527 int i = parent.start; 528 // Since `that` is very likely RandomAccess we could avoid allocating this iterator... 529 for (Object element : that) { 530 if (!(element instanceof Double) || !areEqual(parent.array[i++], (Double) element)) { 531 return false; 532 } 533 } 534 return true; 535 } 536 537 // Because we happen to use the same formula. If that changes, just don't override this. 538 @Override 539 public int hashCode() { 540 return parent.hashCode(); 541 } 542 543 @Override 544 public String toString() { 545 return parent.toString(); 546 } 547 } 548 549 /** 550 * Returns {@code true} if {@code object} is an {@code ImmutableDoubleArray} containing the same 551 * values as this one, in the same order. Values are compared as if by {@link Double#equals}. 552 */ 553 @Override 554 public boolean equals(@CheckForNull Object object) { 555 if (object == this) { 556 return true; 557 } 558 if (!(object instanceof ImmutableDoubleArray)) { 559 return false; 560 } 561 ImmutableDoubleArray that = (ImmutableDoubleArray) object; 562 if (this.length() != that.length()) { 563 return false; 564 } 565 for (int i = 0; i < length(); i++) { 566 if (!areEqual(this.get(i), that.get(i))) { 567 return false; 568 } 569 } 570 return true; 571 } 572 573 // Match the behavior of Double.equals() 574 private static boolean areEqual(double a, double b) { 575 return Double.doubleToLongBits(a) == Double.doubleToLongBits(b); 576 } 577 578 /** Returns an unspecified hash code for the contents of this immutable array. */ 579 @Override 580 public int hashCode() { 581 int hash = 1; 582 for (int i = start; i < end; i++) { 583 hash *= 31; 584 hash += Doubles.hashCode(array[i]); 585 } 586 return hash; 587 } 588 589 /** 590 * Returns a string representation of this array in the same form as {@link 591 * Arrays#toString(double[])}, for example {@code "[1, 2, 3]"}. 592 */ 593 @Override 594 public String toString() { 595 if (isEmpty()) { 596 return "[]"; 597 } 598 StringBuilder builder = new StringBuilder(length() * 5); // rough estimate is fine 599 builder.append('[').append(array[start]); 600 601 for (int i = start + 1; i < end; i++) { 602 builder.append(", ").append(array[i]); 603 } 604 builder.append(']'); 605 return builder.toString(); 606 } 607 608 /** 609 * Returns an immutable array containing the same values as {@code this} array. This is logically 610 * a no-op, and in some circumstances {@code this} itself is returned. However, if this instance 611 * is a {@link #subArray} view of a larger array, this method will copy only the appropriate range 612 * of values, resulting in an equivalent array with a smaller memory footprint. 613 */ 614 public ImmutableDoubleArray trimmed() { 615 return isPartialView() ? new ImmutableDoubleArray(toArray()) : this; 616 } 617 618 private boolean isPartialView() { 619 return start > 0 || end < array.length; 620 } 621 622 Object writeReplace() { 623 return trimmed(); 624 } 625 626 Object readResolve() { 627 return isEmpty() ? EMPTY : this; 628 } 629}