1 /*
2 * Copyright (c) 2009, 2022, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation. Oracle designates this
8 * particular file as subject to the "Classpath" exception as provided
9 * by Oracle in the LICENSE file that accompanied this code.
10 *
11 * This code is distributed in the hope that it will be useful, but WITHOUT
12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
14 * version 2 for more details (a copy is included in the LICENSE file that
15 * accompanied this code).
16 *
17 * You should have received a copy of the GNU General Public License version
18 * 2 along with this work; if not, write to the Free Software Foundation,
19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
20 *
21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
22 * or visit www.oracle.com if you need additional information or have any
23 * questions.
24 */
25
26 package java.util;
27
28 import jdk.internal.util.Preconditions;
29 import jdk.internal.vm.annotation.ForceInline;
30
31 import java.util.function.Supplier;
32
33 /**
34 * This class consists of {@code static} utility methods for operating
35 * on objects, or checking certain conditions before operation. These utilities
36 * include {@code null}-safe or {@code null}-tolerant methods for computing the
37 * hash code of an object, returning a string for an object, comparing two
38 * objects, and checking if indexes or sub-range values are out of bounds.
39 *
40 * @since 1.7
41 */
42 public final class Objects {
43 private Objects() {
44 throw new AssertionError("No java.util.Objects instances for you!");
45 }
46
47 /**
48 * Returns {@code true} if the arguments are equal to each other
49 * and {@code false} otherwise.
50 * Consequently, if both arguments are {@code null}, {@code true}
51 * is returned. Otherwise, if the first argument is not {@code
52 * null}, equality is determined by calling the {@link
53 * Object#equals equals} method of the first argument with the
54 * second argument of this method. Otherwise, {@code false} is
55 * returned.
56 *
57 * @param a an object
58 * @param b an object to be compared with {@code a} for equality
59 * @return {@code true} if the arguments are equal to each other
60 * and {@code false} otherwise
61 * @see Object#equals(Object)
62 */
63 public static boolean equals(Object a, Object b) {
64 return (a == b) || (a != null && a.equals(b));
65 }
66
67 /**
68 * Returns {@code true} if the arguments are deeply equal to each other
69 * and {@code false} otherwise.
70 *
71 * Two {@code null} values are deeply equal. If both arguments are
72 * arrays, the algorithm in {@link Arrays#deepEquals(Object[],
73 * Object[]) Arrays.deepEquals} is used to determine equality.
74 * Otherwise, equality is determined by using the {@link
75 * Object#equals equals} method of the first argument.
76 *
77 * @param a an object
78 * @param b an object to be compared with {@code a} for deep equality
79 * @return {@code true} if the arguments are deeply equal to each other
80 * and {@code false} otherwise
81 * @see Arrays#deepEquals(Object[], Object[])
82 * @see Objects#equals(Object, Object)
83 */
84 public static boolean deepEquals(Object a, Object b) {
85 if (a == b)
86 return true;
87 else if (a == null || b == null)
88 return false;
89 else
90 return Arrays.deepEquals0(a, b);
91 }
92
93 /**
94 * Returns the hash code of a non-{@code null} argument and 0 for
95 * a {@code null} argument.
96 *
97 * @param o an object
98 * @return the hash code of a non-{@code null} argument and 0 for
99 * a {@code null} argument
100 * @see Object#hashCode
101 */
102 public static int hashCode(Object o) {
103 return o != null ? o.hashCode() : 0;
104 }
105
106 /**
107 * Generates a hash code for a sequence of input values. The hash
108 * code is generated as if all the input values were placed into an
109 * array, and that array were hashed by calling {@link
110 * Arrays#hashCode(Object[])}.
111 *
112 * <p>This method is useful for implementing {@link
113 * Object#hashCode()} on objects containing multiple fields. For
114 * example, if an object that has three fields, {@code x}, {@code
115 * y}, and {@code z}, one could write:
116 *
117 * <blockquote><pre>
118 * @Override public int hashCode() {
119 * return Objects.hash(x, y, z);
120 * }
121 * </pre></blockquote>
122 *
123 * <b>Warning: When a single object reference is supplied, the returned
124 * value does not equal the hash code of that object reference.</b> This
125 * value can be computed by calling {@link #hashCode(Object)}.
126 *
127 * @param values the values to be hashed
128 * @return a hash value of the sequence of input values
129 * @see Arrays#hashCode(Object[])
130 * @see List#hashCode
131 */
132 public static int hash(Object... values) {
133 return Arrays.hashCode(values);
134 }
135
136 /**
137 * Returns the result of calling {@code toString} for a non-{@code
138 * null} argument and {@code "null"} for a {@code null} argument.
139 *
140 * @param o an object
141 * @return the result of calling {@code toString} for a non-{@code
142 * null} argument and {@code "null"} for a {@code null} argument
143 * @see Object#toString
144 * @see String#valueOf(Object)
145 */
146 public static String toString(Object o) {
147 return String.valueOf(o);
148 }
149
150 /**
151 * Returns the result of calling {@code toString} on the first
152 * argument if the first argument is not {@code null} and returns
153 * the second argument otherwise.
154 *
155 * @param o an object
156 * @param nullDefault string to return if the first argument is
157 * {@code null}
158 * @return the result of calling {@code toString} on the first
159 * argument if it is not {@code null} and the second argument
160 * otherwise.
161 * @see Objects#toString(Object)
162 */
163 public static String toString(Object o, String nullDefault) {
164 return (o != null) ? o.toString() : nullDefault;
165 }
166
167 /**
168 * {@return a string equivalent to the string returned by {@code
169 * Object.toString} if that method and {@code hashCode} are not
170 * overridden}
171 *
172 * @implNote
173 * This method constructs a string for an object without calling
174 * any overridable methods of the object.
175 *
176 * @implSpec
177 * The method returns a string equivalent to:<br>
178 * {@code o.getClass().getName() + "@" + Integer.toHexString(System.identityHashCode(o))}
179 *
180 * @param o an object
181 * @throws NullPointerException if the argument is null
182 * @see Object#toString
183 * @see System#identityHashCode(Object)
184 * @since 19
185 */
186 public static String toIdentityString(Object o) {
187 requireNonNull(o);
188 return o.getClass().getName() + "@" + Integer.toHexString(System.identityHashCode(o));
189 }
190
191 /**
192 * Returns 0 if the arguments are identical and {@code
193 * c.compare(a, b)} otherwise.
194 * Consequently, if both arguments are {@code null} 0
195 * is returned.
196 *
197 * <p>Note that if one of the arguments is {@code null}, a {@code
198 * NullPointerException} may or may not be thrown depending on
199 * what ordering policy, if any, the {@link Comparator Comparator}
200 * chooses to have for {@code null} values.
201 *
202 * @param <T> the type of the objects being compared
203 * @param a an object
204 * @param b an object to be compared with {@code a}
205 * @param c the {@code Comparator} to compare the first two arguments
206 * @return 0 if the arguments are identical and {@code
207 * c.compare(a, b)} otherwise.
208 * @see Comparable
209 * @see Comparator
210 */
211 public static <T> int compare(T a, T b, Comparator<? super T> c) {
212 return (a == b) ? 0 : c.compare(a, b);
213 }
214
215 /**
216 * Checks that the specified object reference is not {@code null}. This
217 * method is designed primarily for doing parameter validation in methods
218 * and constructors, as demonstrated below:
219 * <blockquote><pre>
220 * public Foo(Bar bar) {
221 * this.bar = Objects.requireNonNull(bar);
222 * }
223 * </pre></blockquote>
224 *
225 * @param obj the object reference to check for nullity
226 * @param <T> the type of the reference
227 * @return {@code obj} if not {@code null}
228 * @throws NullPointerException if {@code obj} is {@code null}
229 */
230 @ForceInline
231 public static <T> T requireNonNull(T obj) {
232 if (obj == null)
233 throw new NullPointerException();
234 return obj;
235 }
236
237 /**
238 * Checks that the specified object reference is not {@code null} and
239 * throws a customized {@link NullPointerException} if it is. This method
240 * is designed primarily for doing parameter validation in methods and
241 * constructors with multiple parameters, as demonstrated below:
242 * <blockquote><pre>
243 * public Foo(Bar bar, Baz baz) {
244 * this.bar = Objects.requireNonNull(bar, "bar must not be null");
245 * this.baz = Objects.requireNonNull(baz, "baz must not be null");
246 * }
247 * </pre></blockquote>
248 *
249 * @param obj the object reference to check for nullity
250 * @param message detail message to be used in the event that a {@code
251 * NullPointerException} is thrown
252 * @param <T> the type of the reference
253 * @return {@code obj} if not {@code null}
254 * @throws NullPointerException if {@code obj} is {@code null}
255 */
256 @ForceInline
257 public static <T> T requireNonNull(T obj, String message) {
258 if (obj == null)
259 throw new NullPointerException(message);
260 return obj;
261 }
262
263 /**
264 * Returns {@code true} if the provided reference is {@code null} otherwise
265 * returns {@code false}.
266 *
267 * @apiNote This method exists to be used as a
268 * {@link java.util.function.Predicate}, {@code filter(Objects::isNull)}
269 *
270 * @param obj a reference to be checked against {@code null}
271 * @return {@code true} if the provided reference is {@code null} otherwise
272 * {@code false}
273 *
274 * @see java.util.function.Predicate
275 * @since 1.8
276 */
277 public static boolean isNull(Object obj) {
278 return obj == null;
279 }
280
281 /**
282 * Returns {@code true} if the provided reference is non-{@code null}
283 * otherwise returns {@code false}.
284 *
285 * @apiNote This method exists to be used as a
286 * {@link java.util.function.Predicate}, {@code filter(Objects::nonNull)}
287 *
288 * @param obj a reference to be checked against {@code null}
289 * @return {@code true} if the provided reference is non-{@code null}
290 * otherwise {@code false}
291 *
292 * @see java.util.function.Predicate
293 * @since 1.8
294 */
295 public static boolean nonNull(Object obj) {
296 return obj != null;
297 }
298
299 /**
300 * Returns the first argument if it is non-{@code null} and
301 * otherwise returns the non-{@code null} second argument.
302 *
303 * @param obj an object
304 * @param defaultObj a non-{@code null} object to return if the first argument
305 * is {@code null}
306 * @param <T> the type of the reference
307 * @return the first argument if it is non-{@code null} and
308 * otherwise the second argument if it is non-{@code null}
309 * @throws NullPointerException if both {@code obj} is null and
310 * {@code defaultObj} is {@code null}
311 * @since 9
312 */
313 public static <T> T requireNonNullElse(T obj, T defaultObj) {
314 return (obj != null) ? obj : requireNonNull(defaultObj, "defaultObj");
315 }
316
317 /**
318 * Returns the first argument if it is non-{@code null} and otherwise
319 * returns the non-{@code null} value of {@code supplier.get()}.
320 *
321 * @param obj an object
322 * @param supplier of a non-{@code null} object to return if the first argument
323 * is {@code null}
324 * @param <T> the type of the first argument and return type
325 * @return the first argument if it is non-{@code null} and otherwise
326 * the value from {@code supplier.get()} if it is non-{@code null}
327 * @throws NullPointerException if both {@code obj} is null and
328 * either the {@code supplier} is {@code null} or
329 * the {@code supplier.get()} value is {@code null}
330 * @since 9
331 */
332 public static <T> T requireNonNullElseGet(T obj, Supplier<? extends T> supplier) {
333 return (obj != null) ? obj
334 : requireNonNull(requireNonNull(supplier, "supplier").get(), "supplier.get()");
335 }
336
337 /**
338 * Checks that the specified object reference is not {@code null} and
339 * throws a customized {@link NullPointerException} if it is.
340 *
341 * <p>Unlike the method {@link #requireNonNull(Object, String)},
342 * this method allows creation of the message to be deferred until
343 * after the null check is made. While this may confer a
344 * performance advantage in the non-null case, when deciding to
345 * call this method care should be taken that the costs of
346 * creating the message supplier are less than the cost of just
347 * creating the string message directly.
348 *
349 * @param obj the object reference to check for nullity
350 * @param messageSupplier supplier of the detail message to be
351 * used in the event that a {@code NullPointerException} is thrown
352 * @param <T> the type of the reference
353 * @return {@code obj} if not {@code null}
354 * @throws NullPointerException if {@code obj} is {@code null}
355 * @since 1.8
356 */
357 public static <T> T requireNonNull(T obj, Supplier<String> messageSupplier) {
358 if (obj == null)
359 throw new NullPointerException(messageSupplier == null ?
360 null : messageSupplier.get());
361 return obj;
362 }
363
364 /**
365 * Checks if the {@code index} is within the bounds of the range from
366 * {@code 0} (inclusive) to {@code length} (exclusive).
367 *
368 * <p>The {@code index} is defined to be out of bounds if any of the
369 * following inequalities is true:
370 * <ul>
371 * <li>{@code index < 0}</li>
372 * <li>{@code index >= length}</li>
373 * <li>{@code length < 0}, which is implied from the former inequalities</li>
374 * </ul>
375 *
376 * @param index the index
377 * @param length the upper-bound (exclusive) of the range
378 * @return {@code index} if it is within bounds of the range
379 * @throws IndexOutOfBoundsException if the {@code index} is out of bounds
380 * @since 9
381 */
382 @ForceInline
383 public static
384 int checkIndex(int index, int length) {
385 return Preconditions.checkIndex(index, length, null);
386 }
387
388 /**
389 * Checks if the sub-range from {@code fromIndex} (inclusive) to
390 * {@code toIndex} (exclusive) is within the bounds of range from {@code 0}
391 * (inclusive) to {@code length} (exclusive).
392 *
393 * <p>The sub-range is defined to be out of bounds if any of the following
394 * inequalities is true:
395 * <ul>
396 * <li>{@code fromIndex < 0}</li>
397 * <li>{@code fromIndex > toIndex}</li>
398 * <li>{@code toIndex > length}</li>
399 * <li>{@code length < 0}, which is implied from the former inequalities</li>
400 * </ul>
401 *
402 * @param fromIndex the lower-bound (inclusive) of the sub-range
403 * @param toIndex the upper-bound (exclusive) of the sub-range
404 * @param length the upper-bound (exclusive) the range
405 * @return {@code fromIndex} if the sub-range within bounds of the range
406 * @throws IndexOutOfBoundsException if the sub-range is out of bounds
407 * @since 9
408 */
409 public static
410 int checkFromToIndex(int fromIndex, int toIndex, int length) {
411 return Preconditions.checkFromToIndex(fromIndex, toIndex, length, null);
412 }
413
414 /**
415 * Checks if the sub-range from {@code fromIndex} (inclusive) to
416 * {@code fromIndex + size} (exclusive) is within the bounds of range from
417 * {@code 0} (inclusive) to {@code length} (exclusive).
418 *
419 * <p>The sub-range is defined to be out of bounds if any of the following
420 * inequalities is true:
421 * <ul>
422 * <li>{@code fromIndex < 0}</li>
423 * <li>{@code size < 0}</li>
424 * <li>{@code fromIndex + size > length}, taking into account integer overflow</li>
425 * <li>{@code length < 0}, which is implied from the former inequalities</li>
426 * </ul>
427 *
428 * @param fromIndex the lower-bound (inclusive) of the sub-interval
429 * @param size the size of the sub-range
430 * @param length the upper-bound (exclusive) of the range
431 * @return {@code fromIndex} if the sub-range within bounds of the range
432 * @throws IndexOutOfBoundsException if the sub-range is out of bounds
433 * @since 9
434 */
435 public static
436 int checkFromIndexSize(int fromIndex, int size, int length) {
437 return Preconditions.checkFromIndexSize(fromIndex, size, length, null);
438 }
439
440 /**
441 * Checks if the {@code index} is within the bounds of the range from
442 * {@code 0} (inclusive) to {@code length} (exclusive).
443 *
444 * <p>The {@code index} is defined to be out of bounds if any of the
445 * following inequalities is true:
446 * <ul>
447 * <li>{@code index < 0}</li>
448 * <li>{@code index >= length}</li>
449 * <li>{@code length < 0}, which is implied from the former inequalities</li>
450 * </ul>
451 *
452 * @param index the index
453 * @param length the upper-bound (exclusive) of the range
454 * @return {@code index} if it is within bounds of the range
455 * @throws IndexOutOfBoundsException if the {@code index} is out of bounds
456 * @since 16
457 */
458 @ForceInline
459 public static
460 long checkIndex(long index, long length) {
461 return Preconditions.checkIndex(index, length, null);
462 }
463
464 /**
465 * Checks if the sub-range from {@code fromIndex} (inclusive) to
466 * {@code toIndex} (exclusive) is within the bounds of range from {@code 0}
467 * (inclusive) to {@code length} (exclusive).
468 *
469 * <p>The sub-range is defined to be out of bounds if any of the following
470 * inequalities is true:
471 * <ul>
472 * <li>{@code fromIndex < 0}</li>
473 * <li>{@code fromIndex > toIndex}</li>
474 * <li>{@code toIndex > length}</li>
475 * <li>{@code length < 0}, which is implied from the former inequalities</li>
476 * </ul>
477 *
478 * @param fromIndex the lower-bound (inclusive) of the sub-range
479 * @param toIndex the upper-bound (exclusive) of the sub-range
480 * @param length the upper-bound (exclusive) the range
481 * @return {@code fromIndex} if the sub-range within bounds of the range
482 * @throws IndexOutOfBoundsException if the sub-range is out of bounds
483 * @since 16
484 */
485 public static
486 long checkFromToIndex(long fromIndex, long toIndex, long length) {
487 return Preconditions.checkFromToIndex(fromIndex, toIndex, length, null);
488 }
489
490 /**
491 * Checks if the sub-range from {@code fromIndex} (inclusive) to
492 * {@code fromIndex + size} (exclusive) is within the bounds of range from
493 * {@code 0} (inclusive) to {@code length} (exclusive).
494 *
495 * <p>The sub-range is defined to be out of bounds if any of the following
496 * inequalities is true:
497 * <ul>
498 * <li>{@code fromIndex < 0}</li>
499 * <li>{@code size < 0}</li>
500 * <li>{@code fromIndex + size > length}, taking into account integer overflow</li>
501 * <li>{@code length < 0}, which is implied from the former inequalities</li>
502 * </ul>
503 *
504 * @param fromIndex the lower-bound (inclusive) of the sub-interval
505 * @param size the size of the sub-range
506 * @param length the upper-bound (exclusive) of the range
507 * @return {@code fromIndex} if the sub-range within bounds of the range
508 * @throws IndexOutOfBoundsException if the sub-range is out of bounds
509 * @since 16
510 */
511 public static
512 long checkFromIndexSize(long fromIndex, long size, long length) {
513 return Preconditions.checkFromIndexSize(fromIndex, size, length, null);
514 }
515 }
--- EOF ---