001 /*
002 * Copyright (C) 2008 The Guava Authors
003 *
004 * Licensed under the Apache License, Version 2.0 (the "License");
005 * you may not use this file except in compliance with the License.
006 * You may obtain a copy of the License at
007 *
008 * http://www.apache.org/licenses/LICENSE-2.0
009 *
010 * Unless required by applicable law or agreed to in writing, software
011 * distributed under the License is distributed on an "AS IS" BASIS,
012 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
013 * See the License for the specific language governing permissions and
014 * limitations under the License.
015 */
016
017 package com.google.common.primitives;
018
019 import static com.google.common.base.Preconditions.checkArgument;
020 import static com.google.common.base.Preconditions.checkElementIndex;
021 import static com.google.common.base.Preconditions.checkNotNull;
022 import static com.google.common.base.Preconditions.checkPositionIndexes;
023
024 import com.google.common.annotations.GwtCompatible;
025 import com.google.common.annotations.GwtIncompatible;
026
027 import java.io.Serializable;
028 import java.util.AbstractList;
029 import java.util.Arrays;
030 import java.util.Collection;
031 import java.util.Collections;
032 import java.util.Comparator;
033 import java.util.List;
034 import java.util.RandomAccess;
035
036 /**
037 * Static utility methods pertaining to {@code int} primitives, that are not
038 * already found in either {@link Integer} or {@link Arrays}.
039 *
040 * @author Kevin Bourrillion
041 * @since 1.0
042 */
043 @GwtCompatible(emulated = true)
044 public final class Ints {
045 private Ints() {}
046
047 /**
048 * The number of bytes required to represent a primitive {@code int}
049 * value.
050 */
051 public static final int BYTES = Integer.SIZE / Byte.SIZE;
052
053 /**
054 * The largest power of two that can be represented as an {@code int}.
055 *
056 * @since 10.0
057 */
058 public static final int MAX_POWER_OF_TWO = 1 << (Integer.SIZE - 2);
059
060 /**
061 * Returns a hash code for {@code value}; equal to the result of invoking
062 * {@code ((Integer) value).hashCode()}.
063 *
064 * @param value a primitive {@code int} value
065 * @return a hash code for the value
066 */
067 public static int hashCode(int value) {
068 return value;
069 }
070
071 /**
072 * Returns the {@code int} value that is equal to {@code value}, if possible.
073 *
074 * @param value any value in the range of the {@code int} type
075 * @return the {@code int} value that equals {@code value}
076 * @throws IllegalArgumentException if {@code value} is greater than {@link
077 * Integer#MAX_VALUE} or less than {@link Integer#MIN_VALUE}
078 */
079 public static int checkedCast(long value) {
080 int result = (int) value;
081 checkArgument(result == value, "Out of range: %s", value);
082 return result;
083 }
084
085 /**
086 * Returns the {@code int} nearest in value to {@code value}.
087 *
088 * @param value any {@code long} value
089 * @return the same value cast to {@code int} if it is in the range of the
090 * {@code int} type, {@link Integer#MAX_VALUE} if it is too large,
091 * or {@link Integer#MIN_VALUE} if it is too small
092 */
093 public static int saturatedCast(long value) {
094 if (value > Integer.MAX_VALUE) {
095 return Integer.MAX_VALUE;
096 }
097 if (value < Integer.MIN_VALUE) {
098 return Integer.MIN_VALUE;
099 }
100 return (int) value;
101 }
102
103 /**
104 * Compares the two specified {@code int} values. The sign of the value
105 * returned is the same as that of {@code ((Integer) a).compareTo(b)}.
106 *
107 * @param a the first {@code int} to compare
108 * @param b the second {@code int} to compare
109 * @return a negative value if {@code a} is less than {@code b}; a positive
110 * value if {@code a} is greater than {@code b}; or zero if they are equal
111 */
112 public static int compare(int a, int b) {
113 return (a < b) ? -1 : ((a > b) ? 1 : 0);
114 }
115
116 /**
117 * Returns {@code true} if {@code target} is present as an element anywhere in
118 * {@code array}.
119 *
120 * @param array an array of {@code int} values, possibly empty
121 * @param target a primitive {@code int} value
122 * @return {@code true} if {@code array[i] == target} for some value of {@code
123 * i}
124 */
125 public static boolean contains(int[] array, int target) {
126 for (int value : array) {
127 if (value == target) {
128 return true;
129 }
130 }
131 return false;
132 }
133
134 /**
135 * Returns the index of the first appearance of the value {@code target} in
136 * {@code array}.
137 *
138 * @param array an array of {@code int} values, possibly empty
139 * @param target a primitive {@code int} value
140 * @return the least index {@code i} for which {@code array[i] == target}, or
141 * {@code -1} if no such index exists.
142 */
143 public static int indexOf(int[] array, int target) {
144 return indexOf(array, target, 0, array.length);
145 }
146
147 // TODO(kevinb): consider making this public
148 private static int indexOf(
149 int[] array, int target, int start, int end) {
150 for (int i = start; i < end; i++) {
151 if (array[i] == target) {
152 return i;
153 }
154 }
155 return -1;
156 }
157
158 /**
159 * Returns the start position of the first occurrence of the specified {@code
160 * target} within {@code array}, or {@code -1} if there is no such occurrence.
161 *
162 * <p>More formally, returns the lowest index {@code i} such that {@code
163 * java.util.Arrays.copyOfRange(array, i, i + target.length)} contains exactly
164 * the same elements as {@code target}.
165 *
166 * @param array the array to search for the sequence {@code target}
167 * @param target the array to search for as a sub-sequence of {@code array}
168 */
169 public static int indexOf(int[] array, int[] target) {
170 checkNotNull(array, "array");
171 checkNotNull(target, "target");
172 if (target.length == 0) {
173 return 0;
174 }
175
176 outer:
177 for (int i = 0; i < array.length - target.length + 1; i++) {
178 for (int j = 0; j < target.length; j++) {
179 if (array[i + j] != target[j]) {
180 continue outer;
181 }
182 }
183 return i;
184 }
185 return -1;
186 }
187
188 /**
189 * Returns the index of the last appearance of the value {@code target} in
190 * {@code array}.
191 *
192 * @param array an array of {@code int} values, possibly empty
193 * @param target a primitive {@code int} value
194 * @return the greatest index {@code i} for which {@code array[i] == target},
195 * or {@code -1} if no such index exists.
196 */
197 public static int lastIndexOf(int[] array, int target) {
198 return lastIndexOf(array, target, 0, array.length);
199 }
200
201 // TODO(kevinb): consider making this public
202 private static int lastIndexOf(
203 int[] array, int target, int start, int end) {
204 for (int i = end - 1; i >= start; i--) {
205 if (array[i] == target) {
206 return i;
207 }
208 }
209 return -1;
210 }
211
212 /**
213 * Returns the least value present in {@code array}.
214 *
215 * @param array a <i>nonempty</i> array of {@code int} values
216 * @return the value present in {@code array} that is less than or equal to
217 * every other value in the array
218 * @throws IllegalArgumentException if {@code array} is empty
219 */
220 public static int min(int... array) {
221 checkArgument(array.length > 0);
222 int min = array[0];
223 for (int i = 1; i < array.length; i++) {
224 if (array[i] < min) {
225 min = array[i];
226 }
227 }
228 return min;
229 }
230
231 /**
232 * Returns the greatest value present in {@code array}.
233 *
234 * @param array a <i>nonempty</i> array of {@code int} values
235 * @return the value present in {@code array} that is greater than or equal to
236 * every other value in the array
237 * @throws IllegalArgumentException if {@code array} is empty
238 */
239 public static int max(int... array) {
240 checkArgument(array.length > 0);
241 int max = array[0];
242 for (int i = 1; i < array.length; i++) {
243 if (array[i] > max) {
244 max = array[i];
245 }
246 }
247 return max;
248 }
249
250 /**
251 * Returns the values from each provided array combined into a single array.
252 * For example, {@code concat(new int[] {a, b}, new int[] {}, new
253 * int[] {c}} returns the array {@code {a, b, c}}.
254 *
255 * @param arrays zero or more {@code int} arrays
256 * @return a single array containing all the values from the source arrays, in
257 * order
258 */
259 public static int[] concat(int[]... arrays) {
260 int length = 0;
261 for (int[] array : arrays) {
262 length += array.length;
263 }
264 int[] result = new int[length];
265 int pos = 0;
266 for (int[] array : arrays) {
267 System.arraycopy(array, 0, result, pos, array.length);
268 pos += array.length;
269 }
270 return result;
271 }
272
273 /**
274 * Returns a big-endian representation of {@code value} in a 4-element byte
275 * array; equivalent to {@code ByteBuffer.allocate(4).putInt(value).array()}.
276 * For example, the input value {@code 0x12131415} would yield the byte array
277 * {@code {0x12, 0x13, 0x14, 0x15}}.
278 *
279 * <p>If you need to convert and concatenate several values (possibly even of
280 * different types), use a shared {@link java.nio.ByteBuffer} instance, or use
281 * {@link com.google.common.io.ByteStreams#newDataOutput()} to get a growable
282 * buffer.
283 */
284 @GwtIncompatible("doesn't work")
285 public static byte[] toByteArray(int value) {
286 return new byte[] {
287 (byte) (value >> 24),
288 (byte) (value >> 16),
289 (byte) (value >> 8),
290 (byte) value};
291 }
292
293 /**
294 * Returns the {@code int} value whose big-endian representation is stored in
295 * the first 4 bytes of {@code bytes}; equivalent to {@code
296 * ByteBuffer.wrap(bytes).getInt()}. For example, the input byte array {@code
297 * {0x12, 0x13, 0x14, 0x15, 0x33}} would yield the {@code int} value {@code
298 * 0x12131415}.
299 *
300 * <p>Arguably, it's preferable to use {@link java.nio.ByteBuffer}; that
301 * library exposes much more flexibility at little cost in readability.
302 *
303 * @throws IllegalArgumentException if {@code bytes} has fewer than 4 elements
304 */
305 @GwtIncompatible("doesn't work")
306 public static int fromByteArray(byte[] bytes) {
307 checkArgument(bytes.length >= BYTES,
308 "array too small: %s < %s", bytes.length, BYTES);
309 return fromBytes(bytes[0], bytes[1], bytes[2], bytes[3]);
310 }
311
312 /**
313 * Returns the {@code int} value whose byte representation is the given 4
314 * bytes, in big-endian order; equivalent to {@code Ints.fromByteArray(new
315 * byte[] {b1, b2, b3, b4})}.
316 *
317 * @since 7.0
318 */
319 @GwtIncompatible("doesn't work")
320 public static int fromBytes(byte b1, byte b2, byte b3, byte b4) {
321 return b1 << 24 | (b2 & 0xFF) << 16 | (b3 & 0xFF) << 8 | (b4 & 0xFF);
322 }
323
324 /**
325 * Returns an array containing the same values as {@code array}, but
326 * guaranteed to be of a specified minimum length. If {@code array} already
327 * has a length of at least {@code minLength}, it is returned directly.
328 * Otherwise, a new array of size {@code minLength + padding} is returned,
329 * containing the values of {@code array}, and zeroes in the remaining places.
330 *
331 * @param array the source array
332 * @param minLength the minimum length the returned array must guarantee
333 * @param padding an extra amount to "grow" the array by if growth is
334 * necessary
335 * @throws IllegalArgumentException if {@code minLength} or {@code padding} is
336 * negative
337 * @return an array containing the values of {@code array}, with guaranteed
338 * minimum length {@code minLength}
339 */
340 public static int[] ensureCapacity(
341 int[] array, int minLength, int padding) {
342 checkArgument(minLength >= 0, "Invalid minLength: %s", minLength);
343 checkArgument(padding >= 0, "Invalid padding: %s", padding);
344 return (array.length < minLength)
345 ? copyOf(array, minLength + padding)
346 : array;
347 }
348
349 // Arrays.copyOf() requires Java 6
350 private static int[] copyOf(int[] original, int length) {
351 int[] copy = new int[length];
352 System.arraycopy(original, 0, copy, 0, Math.min(original.length, length));
353 return copy;
354 }
355
356 /**
357 * Returns a string containing the supplied {@code int} values separated
358 * by {@code separator}. For example, {@code join("-", 1, 2, 3)} returns
359 * the string {@code "1-2-3"}.
360 *
361 * @param separator the text that should appear between consecutive values in
362 * the resulting string (but not at the start or end)
363 * @param array an array of {@code int} values, possibly empty
364 */
365 public static String join(String separator, int... array) {
366 checkNotNull(separator);
367 if (array.length == 0) {
368 return "";
369 }
370
371 // For pre-sizing a builder, just get the right order of magnitude
372 StringBuilder builder = new StringBuilder(array.length * 5);
373 builder.append(array[0]);
374 for (int i = 1; i < array.length; i++) {
375 builder.append(separator).append(array[i]);
376 }
377 return builder.toString();
378 }
379
380 /**
381 * Returns a comparator that compares two {@code int} arrays
382 * lexicographically. That is, it compares, using {@link
383 * #compare(int, int)}), the first pair of values that follow any
384 * common prefix, or when one array is a prefix of the other, treats the
385 * shorter array as the lesser. For example, {@code [] < [1] < [1, 2] < [2]}.
386 *
387 * <p>The returned comparator is inconsistent with {@link
388 * Object#equals(Object)} (since arrays support only identity equality), but
389 * it is consistent with {@link Arrays#equals(int[], int[])}.
390 *
391 * @see <a href="http://en.wikipedia.org/wiki/Lexicographical_order">
392 * Lexicographical order article at Wikipedia</a>
393 * @since 2.0
394 */
395 public static Comparator<int[]> lexicographicalComparator() {
396 return LexicographicalComparator.INSTANCE;
397 }
398
399 private enum LexicographicalComparator implements Comparator<int[]> {
400 INSTANCE;
401
402 @Override
403 public int compare(int[] left, int[] right) {
404 int minLength = Math.min(left.length, right.length);
405 for (int i = 0; i < minLength; i++) {
406 int result = Ints.compare(left[i], right[i]);
407 if (result != 0) {
408 return result;
409 }
410 }
411 return left.length - right.length;
412 }
413 }
414
415 /**
416 * Copies a collection of {@code Integer} instances into a new array of
417 * primitive {@code int} values.
418 *
419 * <p>Elements are copied from the argument collection as if by {@code
420 * collection.toArray()}. Calling this method is as thread-safe as calling
421 * that method.
422 *
423 * @param collection a collection of {@code Integer} objects
424 * @return an array containing the same values as {@code collection}, in the
425 * same order, converted to primitives
426 * @throws NullPointerException if {@code collection} or any of its elements
427 * is null
428 */
429 public static int[] toArray(Collection<Integer> collection) {
430 if (collection instanceof IntArrayAsList) {
431 return ((IntArrayAsList) collection).toIntArray();
432 }
433
434 Object[] boxedArray = collection.toArray();
435 int len = boxedArray.length;
436 int[] array = new int[len];
437 for (int i = 0; i < len; i++) {
438 // checkNotNull for GWT (do not optimize)
439 array[i] = (Integer) checkNotNull(boxedArray[i]);
440 }
441 return array;
442 }
443
444 /**
445 * Returns a fixed-size list backed by the specified array, similar to {@link
446 * Arrays#asList(Object[])}. The list supports {@link List#set(int, Object)},
447 * but any attempt to set a value to {@code null} will result in a {@link
448 * NullPointerException}.
449 *
450 * <p>The returned list maintains the values, but not the identities, of
451 * {@code Integer} objects written to or read from it. For example, whether
452 * {@code list.get(0) == list.get(0)} is true for the returned list is
453 * unspecified.
454 *
455 * @param backingArray the array to back the list
456 * @return a list view of the array
457 */
458 public static List<Integer> asList(int... backingArray) {
459 if (backingArray.length == 0) {
460 return Collections.emptyList();
461 }
462 return new IntArrayAsList(backingArray);
463 }
464
465 @GwtCompatible
466 private static class IntArrayAsList extends AbstractList<Integer>
467 implements RandomAccess, Serializable {
468 final int[] array;
469 final int start;
470 final int end;
471
472 IntArrayAsList(int[] array) {
473 this(array, 0, array.length);
474 }
475
476 IntArrayAsList(int[] array, int start, int end) {
477 this.array = array;
478 this.start = start;
479 this.end = end;
480 }
481
482 @Override public int size() {
483 return end - start;
484 }
485
486 @Override public boolean isEmpty() {
487 return false;
488 }
489
490 @Override public Integer get(int index) {
491 checkElementIndex(index, size());
492 return array[start + index];
493 }
494
495 @Override public boolean contains(Object target) {
496 // Overridden to prevent a ton of boxing
497 return (target instanceof Integer)
498 && Ints.indexOf(array, (Integer) target, start, end) != -1;
499 }
500
501 @Override public int indexOf(Object target) {
502 // Overridden to prevent a ton of boxing
503 if (target instanceof Integer) {
504 int i = Ints.indexOf(array, (Integer) target, start, end);
505 if (i >= 0) {
506 return i - start;
507 }
508 }
509 return -1;
510 }
511
512 @Override public int lastIndexOf(Object target) {
513 // Overridden to prevent a ton of boxing
514 if (target instanceof Integer) {
515 int i = Ints.lastIndexOf(array, (Integer) target, start, end);
516 if (i >= 0) {
517 return i - start;
518 }
519 }
520 return -1;
521 }
522
523 @Override public Integer set(int index, Integer element) {
524 checkElementIndex(index, size());
525 int oldValue = array[start + index];
526 array[start + index] = checkNotNull(element); // checkNotNull for GWT (do not optimize)
527 return oldValue;
528 }
529
530 @Override public List<Integer> subList(int fromIndex, int toIndex) {
531 int size = size();
532 checkPositionIndexes(fromIndex, toIndex, size);
533 if (fromIndex == toIndex) {
534 return Collections.emptyList();
535 }
536 return new IntArrayAsList(array, start + fromIndex, start + toIndex);
537 }
538
539 @Override public boolean equals(Object object) {
540 if (object == this) {
541 return true;
542 }
543 if (object instanceof IntArrayAsList) {
544 IntArrayAsList that = (IntArrayAsList) object;
545 int size = size();
546 if (that.size() != size) {
547 return false;
548 }
549 for (int i = 0; i < size; i++) {
550 if (array[start + i] != that.array[that.start + i]) {
551 return false;
552 }
553 }
554 return true;
555 }
556 return super.equals(object);
557 }
558
559 @Override public int hashCode() {
560 int result = 1;
561 for (int i = start; i < end; i++) {
562 result = 31 * result + Ints.hashCode(array[i]);
563 }
564 return result;
565 }
566
567 @Override public String toString() {
568 StringBuilder builder = new StringBuilder(size() * 5);
569 builder.append('[').append(array[start]);
570 for (int i = start + 1; i < end; i++) {
571 builder.append(", ").append(array[i]);
572 }
573 return builder.append(']').toString();
574 }
575
576 int[] toIntArray() {
577 // Arrays.copyOfRange() requires Java 6
578 int size = size();
579 int[] result = new int[size];
580 System.arraycopy(array, start, result, 0, size);
581 return result;
582 }
583
584 private static final long serialVersionUID = 0;
585 }
586 }