001/* 002 * Copyright (C) 2008 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.checkElementIndex; 019import static com.google.common.base.Preconditions.checkNotNull; 020import static com.google.common.base.Preconditions.checkPositionIndexes; 021import static java.lang.Float.NEGATIVE_INFINITY; 022import static java.lang.Float.POSITIVE_INFINITY; 023 024import com.google.common.annotations.Beta; 025import com.google.common.annotations.GwtCompatible; 026import com.google.common.annotations.GwtIncompatible; 027import com.google.common.base.Converter; 028import java.io.Serializable; 029import java.util.AbstractList; 030import java.util.Arrays; 031import java.util.Collection; 032import java.util.Collections; 033import java.util.Comparator; 034import java.util.List; 035import java.util.RandomAccess; 036import org.checkerframework.checker.nullness.qual.Nullable; 037 038/** 039 * Static utility methods pertaining to {@code float} primitives, that are not already found in 040 * either {@link Float} or {@link Arrays}. 041 * 042 * <p>See the Guava User Guide article on <a 043 * href="https://github.com/google/guava/wiki/PrimitivesExplained">primitive utilities</a>. 044 * 045 * @author Kevin Bourrillion 046 * @since 1.0 047 */ 048@GwtCompatible(emulated = true) 049public final class Floats { 050 private Floats() {} 051 052 /** 053 * The number of bytes required to represent a primitive {@code float} value. 054 * 055 * <p><b>Java 8 users:</b> use {@link Float#BYTES} instead. 056 * 057 * @since 10.0 058 */ 059 public static final int BYTES = Float.SIZE / Byte.SIZE; 060 061 /** 062 * Returns a hash code for {@code value}; equal to the result of invoking {@code ((Float) 063 * value).hashCode()}. 064 * 065 * <p><b>Java 8 users:</b> use {@link Float#hashCode(float)} instead. 066 * 067 * @param value a primitive {@code float} value 068 * @return a hash code for the value 069 */ 070 public static int hashCode(float value) { 071 // TODO(kevinb): is there a better way, that's still gwt-safe? 072 return ((Float) value).hashCode(); 073 } 074 075 /** 076 * Compares the two specified {@code float} values using {@link Float#compare(float, float)}. You 077 * may prefer to invoke that method directly; this method exists only for consistency with the 078 * other utilities in this package. 079 * 080 * <p><b>Note:</b> this method simply delegates to the JDK method {@link Float#compare}. It is 081 * provided for consistency with the other primitive types, whose compare methods were not added 082 * to the JDK until JDK 7. 083 * 084 * @param a the first {@code float} to compare 085 * @param b the second {@code float} to compare 086 * @return the result of invoking {@link Float#compare(float, float)} 087 */ 088 public static int compare(float a, float b) { 089 return Float.compare(a, b); 090 } 091 092 /** 093 * Returns {@code true} if {@code value} represents a real number. This is equivalent to, but not 094 * necessarily implemented as, {@code !(Float.isInfinite(value) || Float.isNaN(value))}. 095 * 096 * <p><b>Java 8 users:</b> use {@link Float#isFinite(float)} instead. 097 * 098 * @since 10.0 099 */ 100 public static boolean isFinite(float value) { 101 return NEGATIVE_INFINITY < value && value < POSITIVE_INFINITY; 102 } 103 104 /** 105 * Returns {@code true} if {@code target} is present as an element anywhere in {@code array}. Note 106 * that this always returns {@code false} when {@code target} is {@code NaN}. 107 * 108 * @param array an array of {@code float} values, possibly empty 109 * @param target a primitive {@code float} value 110 * @return {@code true} if {@code array[i] == target} for some value of {@code i} 111 */ 112 public static boolean contains(float[] array, float target) { 113 for (float value : array) { 114 if (value == target) { 115 return true; 116 } 117 } 118 return false; 119 } 120 121 /** 122 * Returns the index of the first appearance of the value {@code target} in {@code array}. Note 123 * that this always returns {@code -1} when {@code target} is {@code NaN}. 124 * 125 * @param array an array of {@code float} values, possibly empty 126 * @param target a primitive {@code float} value 127 * @return the least index {@code i} for which {@code array[i] == target}, or {@code -1} if no 128 * such index exists. 129 */ 130 public static int indexOf(float[] array, float target) { 131 return indexOf(array, target, 0, array.length); 132 } 133 134 // TODO(kevinb): consider making this public 135 private static int indexOf(float[] array, float target, int start, int end) { 136 for (int i = start; i < end; i++) { 137 if (array[i] == target) { 138 return i; 139 } 140 } 141 return -1; 142 } 143 144 /** 145 * Returns the start position of the first occurrence of the specified {@code target} within 146 * {@code array}, or {@code -1} if there is no such occurrence. 147 * 148 * <p>More formally, returns the lowest index {@code i} such that {@code Arrays.copyOfRange(array, 149 * i, i + target.length)} contains exactly the same elements as {@code target}. 150 * 151 * <p>Note that this always returns {@code -1} when {@code target} contains {@code NaN}. 152 * 153 * @param array the array to search for the sequence {@code target} 154 * @param target the array to search for as a sub-sequence of {@code array} 155 */ 156 public static int indexOf(float[] array, float[] target) { 157 checkNotNull(array, "array"); 158 checkNotNull(target, "target"); 159 if (target.length == 0) { 160 return 0; 161 } 162 163 outer: 164 for (int i = 0; i < array.length - target.length + 1; i++) { 165 for (int j = 0; j < target.length; j++) { 166 if (array[i + j] != target[j]) { 167 continue outer; 168 } 169 } 170 return i; 171 } 172 return -1; 173 } 174 175 /** 176 * Returns the index of the last appearance of the value {@code target} in {@code array}. Note 177 * that this always returns {@code -1} when {@code target} is {@code NaN}. 178 * 179 * @param array an array of {@code float} values, possibly empty 180 * @param target a primitive {@code float} value 181 * @return the greatest index {@code i} for which {@code array[i] == target}, or {@code -1} if no 182 * such index exists. 183 */ 184 public static int lastIndexOf(float[] array, float target) { 185 return lastIndexOf(array, target, 0, array.length); 186 } 187 188 // TODO(kevinb): consider making this public 189 private static int lastIndexOf(float[] array, float target, int start, int end) { 190 for (int i = end - 1; i >= start; i--) { 191 if (array[i] == target) { 192 return i; 193 } 194 } 195 return -1; 196 } 197 198 /** 199 * Returns the least value present in {@code array}, using the same rules of comparison as {@link 200 * Math#min(float, float)}. 201 * 202 * @param array a <i>nonempty</i> array of {@code float} values 203 * @return the value present in {@code array} that is less than or equal to every other value in 204 * the array 205 * @throws IllegalArgumentException if {@code array} is empty 206 */ 207 public static float min(float... array) { 208 checkArgument(array.length > 0); 209 float min = array[0]; 210 for (int i = 1; i < array.length; i++) { 211 min = Math.min(min, array[i]); 212 } 213 return min; 214 } 215 216 /** 217 * Returns the greatest value present in {@code array}, using the same rules of comparison as 218 * {@link Math#max(float, float)}. 219 * 220 * @param array a <i>nonempty</i> array of {@code float} values 221 * @return the value present in {@code array} that is greater than or equal to every other value 222 * in the array 223 * @throws IllegalArgumentException if {@code array} is empty 224 */ 225 public static float max(float... array) { 226 checkArgument(array.length > 0); 227 float max = array[0]; 228 for (int i = 1; i < array.length; i++) { 229 max = Math.max(max, array[i]); 230 } 231 return max; 232 } 233 234 /** 235 * Returns the value nearest to {@code value} which is within the closed range {@code [min..max]}. 236 * 237 * <p>If {@code value} is within the range {@code [min..max]}, {@code value} is returned 238 * unchanged. If {@code value} is less than {@code min}, {@code min} is returned, and if {@code 239 * value} is greater than {@code max}, {@code max} is returned. 240 * 241 * @param value the {@code float} value to constrain 242 * @param min the lower bound (inclusive) of the range to constrain {@code value} to 243 * @param max the upper bound (inclusive) of the range to constrain {@code value} to 244 * @throws IllegalArgumentException if {@code min > max} 245 * @since 21.0 246 */ 247 @Beta 248 public static float constrainToRange(float value, float min, float max) { 249 checkArgument(min <= max, "min (%s) must be less than or equal to max (%s)", min, max); 250 return Math.min(Math.max(value, min), max); 251 } 252 253 /** 254 * Returns the values from each provided array combined into a single array. For example, {@code 255 * concat(new float[] {a, b}, new float[] {}, new float[] {c}} returns the array {@code {a, b, 256 * c}}. 257 * 258 * @param arrays zero or more {@code float} arrays 259 * @return a single array containing all the values from the source arrays, in order 260 */ 261 public static float[] concat(float[]... arrays) { 262 int length = 0; 263 for (float[] array : arrays) { 264 length += array.length; 265 } 266 float[] result = new float[length]; 267 int pos = 0; 268 for (float[] array : arrays) { 269 System.arraycopy(array, 0, result, pos, array.length); 270 pos += array.length; 271 } 272 return result; 273 } 274 275 private static final class FloatConverter extends Converter<String, Float> 276 implements Serializable { 277 static final FloatConverter INSTANCE = new FloatConverter(); 278 279 @Override 280 protected Float doForward(String value) { 281 return Float.valueOf(value); 282 } 283 284 @Override 285 protected String doBackward(Float value) { 286 return value.toString(); 287 } 288 289 @Override 290 public String toString() { 291 return "Floats.stringConverter()"; 292 } 293 294 private Object readResolve() { 295 return INSTANCE; 296 } 297 298 private static final long serialVersionUID = 1; 299 } 300 301 /** 302 * Returns a serializable converter object that converts between strings and floats using {@link 303 * Float#valueOf} and {@link Float#toString()}. 304 * 305 * @since 16.0 306 */ 307 @Beta 308 public static Converter<String, Float> stringConverter() { 309 return FloatConverter.INSTANCE; 310 } 311 312 /** 313 * Returns an array containing the same values as {@code array}, but guaranteed to be of a 314 * specified minimum length. If {@code array} already has a length of at least {@code minLength}, 315 * it is returned directly. Otherwise, a new array of size {@code minLength + padding} is 316 * returned, containing the values of {@code array}, and zeroes in the remaining places. 317 * 318 * @param array the source array 319 * @param minLength the minimum length the returned array must guarantee 320 * @param padding an extra amount to "grow" the array by if growth is necessary 321 * @throws IllegalArgumentException if {@code minLength} or {@code padding} is negative 322 * @return an array containing the values of {@code array}, with guaranteed minimum length {@code 323 * minLength} 324 */ 325 public static float[] ensureCapacity(float[] array, int minLength, int padding) { 326 checkArgument(minLength >= 0, "Invalid minLength: %s", minLength); 327 checkArgument(padding >= 0, "Invalid padding: %s", padding); 328 return (array.length < minLength) ? Arrays.copyOf(array, minLength + padding) : array; 329 } 330 331 /** 332 * Returns a string containing the supplied {@code float} values, converted to strings as 333 * specified by {@link Float#toString(float)}, and separated by {@code separator}. For example, 334 * {@code join("-", 1.0f, 2.0f, 3.0f)} returns the string {@code "1.0-2.0-3.0"}. 335 * 336 * <p>Note that {@link Float#toString(float)} formats {@code float} differently in GWT. In the 337 * previous example, it returns the string {@code "1-2-3"}. 338 * 339 * @param separator the text that should appear between consecutive values in the resulting string 340 * (but not at the start or end) 341 * @param array an array of {@code float} values, possibly empty 342 */ 343 public static String join(String separator, float... array) { 344 checkNotNull(separator); 345 if (array.length == 0) { 346 return ""; 347 } 348 349 // For pre-sizing a builder, just get the right order of magnitude 350 StringBuilder builder = new StringBuilder(array.length * 12); 351 builder.append(array[0]); 352 for (int i = 1; i < array.length; i++) { 353 builder.append(separator).append(array[i]); 354 } 355 return builder.toString(); 356 } 357 358 /** 359 * Returns a comparator that compares two {@code float} arrays <a 360 * href="http://en.wikipedia.org/wiki/Lexicographical_order">lexicographically</a>. That is, it 361 * compares, using {@link #compare(float, float)}), the first pair of values that follow any 362 * common prefix, or when one array is a prefix of the other, treats the shorter array as the 363 * lesser. For example, {@code [] < [1.0f] < [1.0f, 2.0f] < [2.0f]}. 364 * 365 * <p>The returned comparator is inconsistent with {@link Object#equals(Object)} (since arrays 366 * support only identity equality), but it is consistent with {@link Arrays#equals(float[], 367 * float[])}. 368 * 369 * @since 2.0 370 */ 371 public static Comparator<float[]> lexicographicalComparator() { 372 return LexicographicalComparator.INSTANCE; 373 } 374 375 private enum LexicographicalComparator implements Comparator<float[]> { 376 INSTANCE; 377 378 @Override 379 public int compare(float[] left, float[] right) { 380 int minLength = Math.min(left.length, right.length); 381 for (int i = 0; i < minLength; i++) { 382 int result = Float.compare(left[i], right[i]); 383 if (result != 0) { 384 return result; 385 } 386 } 387 return left.length - right.length; 388 } 389 390 @Override 391 public String toString() { 392 return "Floats.lexicographicalComparator()"; 393 } 394 } 395 396 /** 397 * Sorts the elements of {@code array} in descending order. 398 * 399 * <p>Note that this method uses the total order imposed by {@link Float#compare}, which treats 400 * all NaN values as equal and 0.0 as greater than -0.0. 401 * 402 * @since 23.1 403 */ 404 public static void sortDescending(float[] array) { 405 checkNotNull(array); 406 sortDescending(array, 0, array.length); 407 } 408 409 /** 410 * Sorts the elements of {@code array} between {@code fromIndex} inclusive and {@code toIndex} 411 * exclusive in descending order. 412 * 413 * <p>Note that this method uses the total order imposed by {@link Float#compare}, which treats 414 * all NaN values as equal and 0.0 as greater than -0.0. 415 * 416 * @since 23.1 417 */ 418 public static void sortDescending(float[] array, int fromIndex, int toIndex) { 419 checkNotNull(array); 420 checkPositionIndexes(fromIndex, toIndex, array.length); 421 Arrays.sort(array, fromIndex, toIndex); 422 reverse(array, fromIndex, toIndex); 423 } 424 425 /** 426 * Reverses the elements of {@code array}. This is equivalent to {@code 427 * Collections.reverse(Floats.asList(array))}, but is likely to be more efficient. 428 * 429 * @since 23.1 430 */ 431 public static void reverse(float[] array) { 432 checkNotNull(array); 433 reverse(array, 0, array.length); 434 } 435 436 /** 437 * Reverses the elements of {@code array} between {@code fromIndex} inclusive and {@code toIndex} 438 * exclusive. This is equivalent to {@code 439 * Collections.reverse(Floats.asList(array).subList(fromIndex, toIndex))}, but is likely to be 440 * more efficient. 441 * 442 * @throws IndexOutOfBoundsException if {@code fromIndex < 0}, {@code toIndex > array.length}, or 443 * {@code toIndex > fromIndex} 444 * @since 23.1 445 */ 446 public static void reverse(float[] array, int fromIndex, int toIndex) { 447 checkNotNull(array); 448 checkPositionIndexes(fromIndex, toIndex, array.length); 449 for (int i = fromIndex, j = toIndex - 1; i < j; i++, j--) { 450 float tmp = array[i]; 451 array[i] = array[j]; 452 array[j] = tmp; 453 } 454 } 455 456 /** 457 * Returns an array containing each value of {@code collection}, converted to a {@code float} 458 * value in the manner of {@link Number#floatValue}. 459 * 460 * <p>Elements are copied from the argument collection as if by {@code collection.toArray()}. 461 * Calling this method is as thread-safe as calling that method. 462 * 463 * @param collection a collection of {@code Number} instances 464 * @return an array containing the same values as {@code collection}, in the same order, converted 465 * to primitives 466 * @throws NullPointerException if {@code collection} or any of its elements is null 467 * @since 1.0 (parameter was {@code Collection<Float>} before 12.0) 468 */ 469 public static float[] toArray(Collection<? extends Number> collection) { 470 if (collection instanceof FloatArrayAsList) { 471 return ((FloatArrayAsList) collection).toFloatArray(); 472 } 473 474 Object[] boxedArray = collection.toArray(); 475 int len = boxedArray.length; 476 float[] array = new float[len]; 477 for (int i = 0; i < len; i++) { 478 // checkNotNull for GWT (do not optimize) 479 array[i] = ((Number) checkNotNull(boxedArray[i])).floatValue(); 480 } 481 return array; 482 } 483 484 /** 485 * Returns a fixed-size list backed by the specified array, similar to {@link 486 * Arrays#asList(Object[])}. The list supports {@link List#set(int, Object)}, but any attempt to 487 * set a value to {@code null} will result in a {@link NullPointerException}. 488 * 489 * <p>The returned list maintains the values, but not the identities, of {@code Float} objects 490 * written to or read from it. For example, whether {@code list.get(0) == list.get(0)} is true for 491 * the returned list is unspecified. 492 * 493 * <p>The returned list may have unexpected behavior if it contains {@code NaN}, or if {@code NaN} 494 * is used as a parameter to any of its methods. 495 * 496 * @param backingArray the array to back the list 497 * @return a list view of the array 498 */ 499 public static List<Float> asList(float... backingArray) { 500 if (backingArray.length == 0) { 501 return Collections.emptyList(); 502 } 503 return new FloatArrayAsList(backingArray); 504 } 505 506 @GwtCompatible 507 private static class FloatArrayAsList extends AbstractList<Float> 508 implements RandomAccess, Serializable { 509 final float[] array; 510 final int start; 511 final int end; 512 513 FloatArrayAsList(float[] array) { 514 this(array, 0, array.length); 515 } 516 517 FloatArrayAsList(float[] array, int start, int end) { 518 this.array = array; 519 this.start = start; 520 this.end = end; 521 } 522 523 @Override 524 public int size() { 525 return end - start; 526 } 527 528 @Override 529 public boolean isEmpty() { 530 return false; 531 } 532 533 @Override 534 public Float get(int index) { 535 checkElementIndex(index, size()); 536 return array[start + index]; 537 } 538 539 @Override 540 public boolean contains(Object target) { 541 // Overridden to prevent a ton of boxing 542 return (target instanceof Float) && Floats.indexOf(array, (Float) target, start, end) != -1; 543 } 544 545 @Override 546 public int indexOf(Object target) { 547 // Overridden to prevent a ton of boxing 548 if (target instanceof Float) { 549 int i = Floats.indexOf(array, (Float) target, start, end); 550 if (i >= 0) { 551 return i - start; 552 } 553 } 554 return -1; 555 } 556 557 @Override 558 public int lastIndexOf(Object target) { 559 // Overridden to prevent a ton of boxing 560 if (target instanceof Float) { 561 int i = Floats.lastIndexOf(array, (Float) target, start, end); 562 if (i >= 0) { 563 return i - start; 564 } 565 } 566 return -1; 567 } 568 569 @Override 570 public Float set(int index, Float element) { 571 checkElementIndex(index, size()); 572 float oldValue = array[start + index]; 573 // checkNotNull for GWT (do not optimize) 574 array[start + index] = checkNotNull(element); 575 return oldValue; 576 } 577 578 @Override 579 public List<Float> subList(int fromIndex, int toIndex) { 580 int size = size(); 581 checkPositionIndexes(fromIndex, toIndex, size); 582 if (fromIndex == toIndex) { 583 return Collections.emptyList(); 584 } 585 return new FloatArrayAsList(array, start + fromIndex, start + toIndex); 586 } 587 588 @Override 589 public boolean equals(@Nullable Object object) { 590 if (object == this) { 591 return true; 592 } 593 if (object instanceof FloatArrayAsList) { 594 FloatArrayAsList that = (FloatArrayAsList) object; 595 int size = size(); 596 if (that.size() != size) { 597 return false; 598 } 599 for (int i = 0; i < size; i++) { 600 if (array[start + i] != that.array[that.start + i]) { 601 return false; 602 } 603 } 604 return true; 605 } 606 return super.equals(object); 607 } 608 609 @Override 610 public int hashCode() { 611 int result = 1; 612 for (int i = start; i < end; i++) { 613 result = 31 * result + Floats.hashCode(array[i]); 614 } 615 return result; 616 } 617 618 @Override 619 public String toString() { 620 StringBuilder builder = new StringBuilder(size() * 12); 621 builder.append('[').append(array[start]); 622 for (int i = start + 1; i < end; i++) { 623 builder.append(", ").append(array[i]); 624 } 625 return builder.append(']').toString(); 626 } 627 628 float[] toFloatArray() { 629 return Arrays.copyOfRange(array, start, end); 630 } 631 632 private static final long serialVersionUID = 0; 633 } 634 635 /** 636 * Parses the specified string as a single-precision floating point value. The ASCII character 637 * {@code '-'} (<code>'\u002D'</code>) is recognized as the minus sign. 638 * 639 * <p>Unlike {@link Float#parseFloat(String)}, this method returns {@code null} instead of 640 * throwing an exception if parsing fails. Valid inputs are exactly those accepted by {@link 641 * Float#valueOf(String)}, except that leading and trailing whitespace is not permitted. 642 * 643 * <p>This implementation is likely to be faster than {@code Float.parseFloat} if many failures 644 * are expected. 645 * 646 * @param string the string representation of a {@code float} value 647 * @return the floating point value represented by {@code string}, or {@code null} if {@code 648 * string} has a length of zero or cannot be parsed as a {@code float} value 649 * @since 14.0 650 */ 651 @Beta 652 @GwtIncompatible // regular expressions 653 public static @Nullable Float tryParse(String string) { 654 if (Doubles.FLOATING_POINT_PATTERN.matcher(string).matches()) { 655 // TODO(lowasser): could be potentially optimized, but only with 656 // extensive testing 657 try { 658 return Float.parseFloat(string); 659 } catch (NumberFormatException e) { 660 // Float.parseFloat has changed specs several times, so fall through 661 // gracefully 662 } 663 } 664 return null; 665 } 666}