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