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 com.google.common.base.Strings.lenientFormat; 022import static java.lang.Float.NEGATIVE_INFINITY; 023import static java.lang.Float.POSITIVE_INFINITY; 024 025import com.google.common.annotations.GwtCompatible; 026import com.google.common.annotations.GwtIncompatible; 027import com.google.common.annotations.J2ktIncompatible; 028import com.google.common.base.Converter; 029import java.io.Serializable; 030import java.util.AbstractList; 031import java.util.Arrays; 032import java.util.Collection; 033import java.util.Collections; 034import java.util.Comparator; 035import java.util.List; 036import java.util.RandomAccess; 037import javax.annotation.CheckForNull; 038 039/** 040 * Static utility methods pertaining to {@code float} primitives, that are not already found in 041 * either {@link Float} or {@link Arrays}. 042 * 043 * <p>See the Guava User Guide article on <a 044 * href="https://github.com/google/guava/wiki/PrimitivesExplained">primitive utilities</a>. 045 * 046 * @author Kevin Bourrillion 047 * @since 1.0 048 */ 049@GwtCompatible(emulated = true) 050@ElementTypesAreNonnullByDefault 051public final class Floats extends FloatsMethodsForWeb { 052 private Floats() {} 053 054 /** 055 * The number of bytes required to represent a primitive {@code float} value. 056 * 057 * <p><b>Java 8 users:</b> use {@link Float#BYTES} instead. 058 * 059 * @since 10.0 060 */ 061 public static final int BYTES = Float.SIZE / Byte.SIZE; 062 063 /** 064 * Returns a hash code for {@code value}; equal to the result of invoking {@code ((Float) 065 * value).hashCode()}. 066 * 067 * <p><b>Java 8 users:</b> use {@link Float#hashCode(float)} instead. 068 * 069 * @param value a primitive {@code float} value 070 * @return a hash code for the value 071 */ 072 public static int hashCode(float value) { 073 // TODO(kevinb): is there a better way, that's still gwt-safe? 074 return ((Float) value).hashCode(); 075 } 076 077 /** 078 * Compares the two specified {@code float} values using {@link Float#compare(float, float)}. You 079 * may prefer to invoke that method directly; this method exists only for consistency with the 080 * other utilities in this package. 081 * 082 * <p><b>Note:</b> this method simply delegates to the JDK method {@link Float#compare}. It is 083 * provided for consistency with the other primitive types, whose compare methods were not added 084 * to the JDK until JDK 7. 085 * 086 * @param a the first {@code float} to compare 087 * @param b the second {@code float} to compare 088 * @return the result of invoking {@link Float#compare(float, float)} 089 */ 090 public static int compare(float a, float b) { 091 return Float.compare(a, b); 092 } 093 094 /** 095 * Returns {@code true} if {@code value} represents a real number. This is equivalent to, but not 096 * necessarily implemented as, {@code !(Float.isInfinite(value) || Float.isNaN(value))}. 097 * 098 * <p><b>Java 8 users:</b> use {@link Float#isFinite(float)} instead. 099 * 100 * @since 10.0 101 */ 102 public static boolean isFinite(float value) { 103 return NEGATIVE_INFINITY < value && value < POSITIVE_INFINITY; 104 } 105 106 /** 107 * Returns {@code true} if {@code target} is present as an element anywhere in {@code array}. Note 108 * that this always returns {@code false} when {@code target} is {@code NaN}. 109 * 110 * @param array an array of {@code float} values, possibly empty 111 * @param target a primitive {@code float} value 112 * @return {@code true} if {@code array[i] == target} for some value of {@code i} 113 */ 114 public static boolean contains(float[] array, float target) { 115 for (float value : array) { 116 if (value == target) { 117 return true; 118 } 119 } 120 return false; 121 } 122 123 /** 124 * Returns the index of the first appearance of the value {@code target} in {@code array}. Note 125 * that this always returns {@code -1} when {@code target} is {@code NaN}. 126 * 127 * @param array an array of {@code float} values, possibly empty 128 * @param target a primitive {@code float} value 129 * @return the least index {@code i} for which {@code array[i] == target}, or {@code -1} if no 130 * such index exists. 131 */ 132 public static int indexOf(float[] array, float target) { 133 return indexOf(array, target, 0, array.length); 134 } 135 136 // TODO(kevinb): consider making this public 137 private static int indexOf(float[] array, float target, int start, int end) { 138 for (int i = start; i < end; i++) { 139 if (array[i] == target) { 140 return i; 141 } 142 } 143 return -1; 144 } 145 146 /** 147 * Returns the start position of the first occurrence of the specified {@code target} within 148 * {@code array}, or {@code -1} if there is no such occurrence. 149 * 150 * <p>More formally, returns the lowest index {@code i} such that {@code Arrays.copyOfRange(array, 151 * i, i + target.length)} contains exactly the same elements as {@code target}. 152 * 153 * <p>Note that this always returns {@code -1} when {@code target} contains {@code NaN}. 154 * 155 * @param array the array to search for the sequence {@code target} 156 * @param target the array to search for as a sub-sequence of {@code array} 157 */ 158 public static int indexOf(float[] array, float[] target) { 159 checkNotNull(array, "array"); 160 checkNotNull(target, "target"); 161 if (target.length == 0) { 162 return 0; 163 } 164 165 outer: 166 for (int i = 0; i < array.length - target.length + 1; i++) { 167 for (int j = 0; j < target.length; j++) { 168 if (array[i + j] != target[j]) { 169 continue outer; 170 } 171 } 172 return i; 173 } 174 return -1; 175 } 176 177 /** 178 * Returns the index of the last appearance of the value {@code target} in {@code array}. Note 179 * that this always returns {@code -1} when {@code target} is {@code NaN}. 180 * 181 * @param array an array of {@code float} values, possibly empty 182 * @param target a primitive {@code float} value 183 * @return the greatest index {@code i} for which {@code array[i] == target}, or {@code -1} if no 184 * such index exists. 185 */ 186 public static int lastIndexOf(float[] array, float target) { 187 return lastIndexOf(array, target, 0, array.length); 188 } 189 190 // TODO(kevinb): consider making this public 191 private static int lastIndexOf(float[] array, float target, int start, int end) { 192 for (int i = end - 1; i >= start; i--) { 193 if (array[i] == target) { 194 return i; 195 } 196 } 197 return -1; 198 } 199 200 /** 201 * Returns the least value present in {@code array}, using the same rules of comparison as {@link 202 * Math#min(float, float)}. 203 * 204 * @param array a <i>nonempty</i> array of {@code float} values 205 * @return the value present in {@code array} that is less than or equal to every other value in 206 * the array 207 * @throws IllegalArgumentException if {@code array} is empty 208 */ 209 @GwtIncompatible( 210 "Available in GWT! Annotation is to avoid conflict with GWT specialization of base class.") 211 public static float min(float... array) { 212 checkArgument(array.length > 0); 213 float min = array[0]; 214 for (int i = 1; i < array.length; i++) { 215 min = Math.min(min, array[i]); 216 } 217 return min; 218 } 219 220 /** 221 * Returns the greatest value present in {@code array}, using the same rules of comparison as 222 * {@link Math#max(float, float)}. 223 * 224 * @param array a <i>nonempty</i> array of {@code float} values 225 * @return the value present in {@code array} that is greater than or equal to every other value 226 * in the array 227 * @throws IllegalArgumentException if {@code array} is empty 228 */ 229 @GwtIncompatible( 230 "Available in GWT! Annotation is to avoid conflict with GWT specialization of base class.") 231 public static float max(float... array) { 232 checkArgument(array.length > 0); 233 float max = array[0]; 234 for (int i = 1; i < array.length; i++) { 235 max = Math.max(max, array[i]); 236 } 237 return max; 238 } 239 240 /** 241 * Returns the value nearest to {@code value} which is within the closed range {@code [min..max]}. 242 * 243 * <p>If {@code value} is within the range {@code [min..max]}, {@code value} is returned 244 * unchanged. If {@code value} is less than {@code min}, {@code min} is returned, and if {@code 245 * value} is greater than {@code max}, {@code max} is returned. 246 * 247 * @param value the {@code float} value to constrain 248 * @param min the lower bound (inclusive) of the range to constrain {@code value} to 249 * @param max the upper bound (inclusive) of the range to constrain {@code value} to 250 * @throws IllegalArgumentException if {@code min > max} 251 * @since 21.0 252 */ 253 public static float constrainToRange(float value, float min, float max) { 254 // avoid auto-boxing by not using Preconditions.checkArgument(); see Guava issue 3984 255 // Reject NaN by testing for the good case (min <= max) instead of the bad (min > max). 256 if (min <= max) { 257 return Math.min(Math.max(value, min), max); 258 } 259 throw new IllegalArgumentException( 260 lenientFormat("min (%s) must be less than or equal to max (%s)", min, max)); 261 } 262 263 /** 264 * Returns the values from each provided array combined into a single array. For example, {@code 265 * concat(new float[] {a, b}, new float[] {}, new float[] {c}} returns the array {@code {a, b, 266 * c}}. 267 * 268 * @param arrays zero or more {@code float} arrays 269 * @return a single array containing all the values from the source arrays, in order 270 */ 271 public static float[] concat(float[]... arrays) { 272 int length = 0; 273 for (float[] array : arrays) { 274 length += array.length; 275 } 276 float[] result = new float[length]; 277 int pos = 0; 278 for (float[] array : arrays) { 279 System.arraycopy(array, 0, result, pos, array.length); 280 pos += array.length; 281 } 282 return result; 283 } 284 285 private static final class FloatConverter extends Converter<String, Float> 286 implements Serializable { 287 static final FloatConverter INSTANCE = new FloatConverter(); 288 289 @Override 290 protected Float doForward(String value) { 291 return Float.valueOf(value); 292 } 293 294 @Override 295 protected String doBackward(Float value) { 296 return value.toString(); 297 } 298 299 @Override 300 public String toString() { 301 return "Floats.stringConverter()"; 302 } 303 304 private Object readResolve() { 305 return INSTANCE; 306 } 307 308 private static final long serialVersionUID = 1; 309 } 310 311 /** 312 * Returns a serializable converter object that converts between strings and floats using {@link 313 * Float#valueOf} and {@link Float#toString()}. 314 * 315 * @since 16.0 316 */ 317 public static Converter<String, Float> stringConverter() { 318 return FloatConverter.INSTANCE; 319 } 320 321 /** 322 * Returns an array containing the same values as {@code array}, but guaranteed to be of a 323 * specified minimum length. If {@code array} already has a length of at least {@code minLength}, 324 * it is returned directly. Otherwise, a new array of size {@code minLength + padding} is 325 * returned, containing the values of {@code array}, and zeroes in the remaining places. 326 * 327 * @param array the source array 328 * @param minLength the minimum length the returned array must guarantee 329 * @param padding an extra amount to "grow" the array by if growth is necessary 330 * @throws IllegalArgumentException if {@code minLength} or {@code padding} is negative 331 * @return an array containing the values of {@code array}, with guaranteed minimum length {@code 332 * minLength} 333 */ 334 public static float[] ensureCapacity(float[] array, int minLength, int padding) { 335 checkArgument(minLength >= 0, "Invalid minLength: %s", minLength); 336 checkArgument(padding >= 0, "Invalid padding: %s", padding); 337 return (array.length < minLength) ? Arrays.copyOf(array, minLength + padding) : array; 338 } 339 340 /** 341 * Returns a string containing the supplied {@code float} values, converted to strings as 342 * specified by {@link Float#toString(float)}, and separated by {@code separator}. For example, 343 * {@code join("-", 1.0f, 2.0f, 3.0f)} returns the string {@code "1.0-2.0-3.0"}. 344 * 345 * <p>Note that {@link Float#toString(float)} formats {@code float} differently in GWT. In the 346 * previous example, it returns the string {@code "1-2-3"}. 347 * 348 * @param separator the text that should appear between consecutive values in the resulting string 349 * (but not at the start or end) 350 * @param array an array of {@code float} values, possibly empty 351 */ 352 public static String join(String separator, float... array) { 353 checkNotNull(separator); 354 if (array.length == 0) { 355 return ""; 356 } 357 358 // For pre-sizing a builder, just get the right order of magnitude 359 StringBuilder builder = new StringBuilder(array.length * 12); 360 builder.append(array[0]); 361 for (int i = 1; i < array.length; i++) { 362 builder.append(separator).append(array[i]); 363 } 364 return builder.toString(); 365 } 366 367 /** 368 * Returns a comparator that compares two {@code float} arrays <a 369 * href="http://en.wikipedia.org/wiki/Lexicographical_order">lexicographically</a>. That is, it 370 * compares, using {@link #compare(float, float)}), the first pair of values that follow any 371 * common prefix, or when one array is a prefix of the other, treats the shorter array as the 372 * lesser. For example, {@code [] < [1.0f] < [1.0f, 2.0f] < [2.0f]}. 373 * 374 * <p>The returned comparator is inconsistent with {@link Object#equals(Object)} (since arrays 375 * support only identity equality), but it is consistent with {@link Arrays#equals(float[], 376 * float[])}. 377 * 378 * @since 2.0 379 */ 380 public static Comparator<float[]> lexicographicalComparator() { 381 return LexicographicalComparator.INSTANCE; 382 } 383 384 private enum LexicographicalComparator implements Comparator<float[]> { 385 INSTANCE; 386 387 @Override 388 public int compare(float[] left, float[] right) { 389 int minLength = Math.min(left.length, right.length); 390 for (int i = 0; i < minLength; i++) { 391 int result = Float.compare(left[i], right[i]); 392 if (result != 0) { 393 return result; 394 } 395 } 396 return left.length - right.length; 397 } 398 399 @Override 400 public String toString() { 401 return "Floats.lexicographicalComparator()"; 402 } 403 } 404 405 /** 406 * Sorts the elements of {@code array} in descending order. 407 * 408 * <p>Note that this method uses the total order imposed by {@link Float#compare}, which treats 409 * all NaN values as equal and 0.0 as greater than -0.0. 410 * 411 * @since 23.1 412 */ 413 public static void sortDescending(float[] array) { 414 checkNotNull(array); 415 sortDescending(array, 0, array.length); 416 } 417 418 /** 419 * Sorts the elements of {@code array} between {@code fromIndex} inclusive and {@code toIndex} 420 * exclusive in descending order. 421 * 422 * <p>Note that this method uses the total order imposed by {@link Float#compare}, which treats 423 * all NaN values as equal and 0.0 as greater than -0.0. 424 * 425 * @since 23.1 426 */ 427 public static void sortDescending(float[] array, int fromIndex, int toIndex) { 428 checkNotNull(array); 429 checkPositionIndexes(fromIndex, toIndex, array.length); 430 Arrays.sort(array, fromIndex, toIndex); 431 reverse(array, fromIndex, toIndex); 432 } 433 434 /** 435 * Reverses the elements of {@code array}. This is equivalent to {@code 436 * Collections.reverse(Floats.asList(array))}, but is likely to be more efficient. 437 * 438 * @since 23.1 439 */ 440 public static void reverse(float[] array) { 441 checkNotNull(array); 442 reverse(array, 0, array.length); 443 } 444 445 /** 446 * Reverses the elements of {@code array} between {@code fromIndex} inclusive and {@code toIndex} 447 * exclusive. This is equivalent to {@code 448 * Collections.reverse(Floats.asList(array).subList(fromIndex, toIndex))}, but is likely to be 449 * more efficient. 450 * 451 * @throws IndexOutOfBoundsException if {@code fromIndex < 0}, {@code toIndex > array.length}, or 452 * {@code toIndex > fromIndex} 453 * @since 23.1 454 */ 455 public static void reverse(float[] array, int fromIndex, int toIndex) { 456 checkNotNull(array); 457 checkPositionIndexes(fromIndex, toIndex, array.length); 458 for (int i = fromIndex, j = toIndex - 1; i < j; i++, j--) { 459 float tmp = array[i]; 460 array[i] = array[j]; 461 array[j] = tmp; 462 } 463 } 464 465 /** 466 * Performs a right rotation of {@code array} of "distance" places, so that the first element is 467 * moved to index "distance", and the element at index {@code i} ends up at index {@code (distance 468 * + i) mod array.length}. This is equivalent to {@code Collections.rotate(Floats.asList(array), 469 * distance)}, but is considerably faster and avoids allocation and garbage collection. 470 * 471 * <p>The provided "distance" may be negative, which will rotate left. 472 * 473 * @since 32.0.0 474 */ 475 public static void rotate(float[] array, int distance) { 476 rotate(array, distance, 0, array.length); 477 } 478 479 /** 480 * Performs a right rotation of {@code array} between {@code fromIndex} inclusive and {@code 481 * toIndex} exclusive. This is equivalent to {@code 482 * Collections.rotate(Floats.asList(array).subList(fromIndex, toIndex), distance)}, but is 483 * considerably faster and avoids allocations and garbage collection. 484 * 485 * <p>The provided "distance" may be negative, which will rotate left. 486 * 487 * @throws IndexOutOfBoundsException if {@code fromIndex < 0}, {@code toIndex > array.length}, or 488 * {@code toIndex > fromIndex} 489 * @since 32.0.0 490 */ 491 public static void rotate(float[] array, int distance, int fromIndex, int toIndex) { 492 // See Ints.rotate for more details about possible algorithms here. 493 checkNotNull(array); 494 checkPositionIndexes(fromIndex, toIndex, array.length); 495 if (array.length <= 1) { 496 return; 497 } 498 499 int length = toIndex - fromIndex; 500 // Obtain m = (-distance mod length), a non-negative value less than "length". This is how many 501 // places left to rotate. 502 int m = -distance % length; 503 m = (m < 0) ? m + length : m; 504 // The current index of what will become the first element of the rotated section. 505 int newFirstIndex = m + fromIndex; 506 if (newFirstIndex == fromIndex) { 507 return; 508 } 509 510 reverse(array, fromIndex, newFirstIndex); 511 reverse(array, newFirstIndex, toIndex); 512 reverse(array, fromIndex, toIndex); 513 } 514 515 /** 516 * Returns an array containing each value of {@code collection}, converted to a {@code float} 517 * value in the manner of {@link Number#floatValue}. 518 * 519 * <p>Elements are copied from the argument collection as if by {@code collection.toArray()}. 520 * Calling this method is as thread-safe as calling that method. 521 * 522 * @param collection a collection of {@code Number} instances 523 * @return an array containing the same values as {@code collection}, in the same order, converted 524 * to primitives 525 * @throws NullPointerException if {@code collection} or any of its elements is null 526 * @since 1.0 (parameter was {@code Collection<Float>} before 12.0) 527 */ 528 public static float[] toArray(Collection<? extends Number> collection) { 529 if (collection instanceof FloatArrayAsList) { 530 return ((FloatArrayAsList) collection).toFloatArray(); 531 } 532 533 Object[] boxedArray = collection.toArray(); 534 int len = boxedArray.length; 535 float[] array = new float[len]; 536 for (int i = 0; i < len; i++) { 537 // checkNotNull for GWT (do not optimize) 538 array[i] = ((Number) checkNotNull(boxedArray[i])).floatValue(); 539 } 540 return array; 541 } 542 543 /** 544 * Returns a fixed-size list backed by the specified array, similar to {@link 545 * Arrays#asList(Object[])}. The list supports {@link List#set(int, Object)}, but any attempt to 546 * set a value to {@code null} will result in a {@link NullPointerException}. 547 * 548 * <p>The returned list maintains the values, but not the identities, of {@code Float} objects 549 * written to or read from it. For example, whether {@code list.get(0) == list.get(0)} is true for 550 * the returned list is unspecified. 551 * 552 * <p>The returned list may have unexpected behavior if it contains {@code NaN}, or if {@code NaN} 553 * is used as a parameter to any of its methods. 554 * 555 * <p>The returned list is serializable. 556 * 557 * @param backingArray the array to back the list 558 * @return a list view of the array 559 */ 560 public static List<Float> asList(float... backingArray) { 561 if (backingArray.length == 0) { 562 return Collections.emptyList(); 563 } 564 return new FloatArrayAsList(backingArray); 565 } 566 567 @GwtCompatible 568 private static class FloatArrayAsList extends AbstractList<Float> 569 implements RandomAccess, Serializable { 570 final float[] array; 571 final int start; 572 final int end; 573 574 FloatArrayAsList(float[] array) { 575 this(array, 0, array.length); 576 } 577 578 FloatArrayAsList(float[] array, int start, int end) { 579 this.array = array; 580 this.start = start; 581 this.end = end; 582 } 583 584 @Override 585 public int size() { 586 return end - start; 587 } 588 589 @Override 590 public boolean isEmpty() { 591 return false; 592 } 593 594 @Override 595 public Float get(int index) { 596 checkElementIndex(index, size()); 597 return array[start + index]; 598 } 599 600 @Override 601 public boolean contains(@CheckForNull Object target) { 602 // Overridden to prevent a ton of boxing 603 return (target instanceof Float) && Floats.indexOf(array, (Float) target, start, end) != -1; 604 } 605 606 @Override 607 public int indexOf(@CheckForNull Object target) { 608 // Overridden to prevent a ton of boxing 609 if (target instanceof Float) { 610 int i = Floats.indexOf(array, (Float) target, start, end); 611 if (i >= 0) { 612 return i - start; 613 } 614 } 615 return -1; 616 } 617 618 @Override 619 public int lastIndexOf(@CheckForNull Object target) { 620 // Overridden to prevent a ton of boxing 621 if (target instanceof Float) { 622 int i = Floats.lastIndexOf(array, (Float) target, start, end); 623 if (i >= 0) { 624 return i - start; 625 } 626 } 627 return -1; 628 } 629 630 @Override 631 public Float set(int index, Float element) { 632 checkElementIndex(index, size()); 633 float oldValue = array[start + index]; 634 // checkNotNull for GWT (do not optimize) 635 array[start + index] = checkNotNull(element); 636 return oldValue; 637 } 638 639 @Override 640 public List<Float> subList(int fromIndex, int toIndex) { 641 int size = size(); 642 checkPositionIndexes(fromIndex, toIndex, size); 643 if (fromIndex == toIndex) { 644 return Collections.emptyList(); 645 } 646 return new FloatArrayAsList(array, start + fromIndex, start + toIndex); 647 } 648 649 @Override 650 public boolean equals(@CheckForNull Object object) { 651 if (object == this) { 652 return true; 653 } 654 if (object instanceof FloatArrayAsList) { 655 FloatArrayAsList that = (FloatArrayAsList) object; 656 int size = size(); 657 if (that.size() != size) { 658 return false; 659 } 660 for (int i = 0; i < size; i++) { 661 if (array[start + i] != that.array[that.start + i]) { 662 return false; 663 } 664 } 665 return true; 666 } 667 return super.equals(object); 668 } 669 670 @Override 671 public int hashCode() { 672 int result = 1; 673 for (int i = start; i < end; i++) { 674 result = 31 * result + Floats.hashCode(array[i]); 675 } 676 return result; 677 } 678 679 @Override 680 public String toString() { 681 StringBuilder builder = new StringBuilder(size() * 12); 682 builder.append('[').append(array[start]); 683 for (int i = start + 1; i < end; i++) { 684 builder.append(", ").append(array[i]); 685 } 686 return builder.append(']').toString(); 687 } 688 689 float[] toFloatArray() { 690 return Arrays.copyOfRange(array, start, end); 691 } 692 693 private static final long serialVersionUID = 0; 694 } 695 696 /** 697 * Parses the specified string as a single-precision floating point value. The ASCII character 698 * {@code '-'} (<code>'\u002D'</code>) is recognized as the minus sign. 699 * 700 * <p>Unlike {@link Float#parseFloat(String)}, this method returns {@code null} instead of 701 * throwing an exception if parsing fails. Valid inputs are exactly those accepted by {@link 702 * Float#valueOf(String)}, except that leading and trailing whitespace is not permitted. 703 * 704 * <p>This implementation is likely to be faster than {@code Float.parseFloat} if many failures 705 * are expected. 706 * 707 * @param string the string representation of a {@code float} value 708 * @return the floating point value represented by {@code string}, or {@code null} if {@code 709 * string} has a length of zero or cannot be parsed as a {@code float} value 710 * @throws NullPointerException if {@code string} is {@code null} 711 * @since 14.0 712 */ 713 @J2ktIncompatible 714 @GwtIncompatible // regular expressions 715 @CheckForNull 716 public static Float tryParse(String string) { 717 if (Doubles.FLOATING_POINT_PATTERN.matcher(string).matches()) { 718 // TODO(lowasser): could be potentially optimized, but only with 719 // extensive testing 720 try { 721 return Float.parseFloat(string); 722 } catch (NumberFormatException e) { 723 // Float.parseFloat has changed specs several times, so fall through 724 // gracefully 725 } 726 } 727 return null; 728 } 729}