1 /*
2 * Copyright (c) 2009, 2025, 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.javac.PreviewFeature;
29 import jdk.internal.misc.PreviewFeatures;
30 import jdk.internal.util.Preconditions;
31 import jdk.internal.vm.annotation.ForceInline;
32
33 import java.util.function.Supplier;
34
35 /**
36 * This class consists of {@code static} utility methods for operating
37 * on objects, or checking certain conditions before operation. These utilities
38 * include {@code null}-safe or {@code null}-tolerant methods for computing the
39 * hash code of an object, returning a string for an object, comparing two
40 * objects, and checking if indexes or sub-range values are out of bounds.
41 *
42 * @since 1.7
43 */
44 public final class Objects {
45 private Objects() {
46 throw new AssertionError("No java.util.Objects instances for you!");
47 }
48
49 /**
50 * {@return {@code true} if the arguments are equal to each other
51 * and {@code false} otherwise}
52 * Consequently, if both arguments are {@code null}, {@code true}
53 * is returned. Otherwise, if the first argument is not {@code
54 * null}, equality is determined by calling the {@link
55 * Object#equals equals} method of the first argument with the
56 * second argument of this method. Otherwise, {@code false} is
57 * returned.
58 *
59 * @param a an object
60 * @param b an object to be compared with {@code a} for equality
61 * @see Object#equals(Object)
62 */
63 public static boolean equals(Object a, Object b) {
64 if (PreviewFeatures.isEnabled()) {
65 // With --enable-preview avoid acmp
66 return (a == null) ? b == null : a.equals(b);
67 } else {
68 return (a == b) || (a != null && a.equals(b));
69 }
70 }
71
72 /**
73 * {@return {@code true} if the arguments are deeply equal to each other
74 * and {@code false} otherwise}
75 *
76 * Two {@code null} values are deeply equal. If both arguments are
77 * arrays, the algorithm in {@link Arrays#deepEquals(Object[],
78 * Object[]) Arrays.deepEquals} is used to determine equality.
79 * Otherwise, equality is determined by using the {@link
80 * Object#equals equals} method of the first argument.
81 *
82 * @param a an object
83 * @param b an object to be compared with {@code a} for deep equality
84 * @see Arrays#deepEquals(Object[], Object[])
85 * @see Objects#equals(Object, Object)
86 */
87 public static boolean deepEquals(Object a, Object b) {
88 if (a == b)
89 return true;
90 else if (a == null || b == null)
91 return false;
92 else
93 return Arrays.deepEquals0(a, b);
94 }
95
96 /**
97 * {@return the hash code of a non-{@code null} argument and 0 for
98 * a {@code null} argument}
99 *
100 * @param o an object
101 * @see Object#hashCode
102 */
103 public static int hashCode(Object o) {
104 return o != null ? o.hashCode() : 0;
105 }
106
107 /**
108 * {@return a hash code for a sequence of input values} The hash
109 * code is generated as if all the input values were placed into an
110 * array, and that array were hashed by calling {@link
111 * Arrays#hashCode(Object[])}.
112 *
113 * <p>This method is useful for implementing {@link
114 * Object#hashCode()} on objects containing multiple fields. For
115 * example, if an object that has three fields, {@code x}, {@code
116 * y}, and {@code z}, one could write:
117 *
118 * <blockquote><pre>
119 * @Override public int hashCode() {
120 * return Objects.hash(x, y, z);
121 * }
122 * </pre></blockquote>
123 *
124 * <b>Warning: When a single object reference is supplied, the returned
125 * value does not equal the hash code of that object reference.</b> This
126 * value can be computed by calling {@link #hashCode(Object)}.
127 *
128 * @param values the values to be hashed
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 * {@return the result of calling {@code toString} for a
138 * non-{@code null} argument and {@code "null"} for a
139 * {@code null} argument}
140 *
141 * @param o an object
142 * @see Object#toString
143 * @see String#valueOf(Object)
144 */
145 public static String toString(Object o) {
146 return String.valueOf(o);
147 }
148
149 /**
150 * {@return the result of calling {@code toString} on the first
151 * argument if the first argument is not {@code null} and the
152 * second argument otherwise}
153 *
154 * @param o an object
155 * @param nullDefault string to return if the first argument is
156 * {@code null}
157 * @see Objects#toString(Object)
158 */
159 public static String toString(Object o, String nullDefault) {
160 return (o != null) ? o.toString() : nullDefault;
161 }
162
163 /**
164 * {@return a string equivalent to the string returned by {@code
165 * Object.toString} if that method and {@code hashCode} are not
166 * overridden}
167 *
168 * @implNote
169 * This method constructs a string for an object without calling
170 * any overridable methods of the object.
171 *
172 * @implSpec
173 * The method returns a string equivalent to:<br>
174 * {@code o.getClass().getName() + "@" + Integer.toHexString(System.identityHashCode(o))}
175 *
176 * @param o an object
177 * @throws NullPointerException if the argument is null
178 * @see Object#toString
179 * @see System#identityHashCode(Object)
180 * @since 19
181 */
182 public static String toIdentityString(Object o) {
183 requireNonNull(o);
184 return o.getClass().getName() + "@" + Integer.toHexString(System.identityHashCode(o));
185 }
186
187 /**
188 * {@return {@code true} if the object is a non-null reference
189 * to an {@linkplain Class#isIdentity() identity object}, otherwise {@code false}}
190 *
191 * @apiNote
192 * If the parameter is {@code null}, there is no object
193 * and hence no class to check for identity; the return is {@code false}.
194 * To test for a {@linkplain Class#isValue() value object} use:
195 * {@snippet type="java" :
196 * if (obj != null && !Objects.hasIdentity(obj)) {
197 * // obj is a non-null value object
198 * }
199 * }
200 * @param obj an object or {@code null}
201 * @since Valhalla
202 */
203 @PreviewFeature(feature = PreviewFeature.Feature.VALUE_OBJECTS)
204 // @IntrinsicCandidate
205 public static boolean hasIdentity(Object obj) {
206 return (obj == null) ? false : obj.getClass().isIdentity();
207 }
208
209 /**
210 * {@return {@code true} if the object is a non-null reference
211 * to a {@linkplain Class#isValue() value object}, otherwise {@code false}}
212 *
213 * @param obj an object or {@code null}
214 * @since Valhalla
215 */
216 @PreviewFeature(feature = PreviewFeature.Feature.VALUE_OBJECTS)
217 // @IntrinsicCandidate
218 public static boolean isValueObject(Object obj) {
219 return (obj == null) ? false : obj.getClass().isValue();
220 }
221
222 /**
223 * Checks that the specified object reference is an identity object.
224 *
225 * @param obj the object reference to check for identity
226 * @param <T> the type of the reference
227 * @return {@code obj} if {@code obj} is an identity object
228 * @throws NullPointerException if {@code obj} is {@code null}
229 * @throws IdentityException if {@code obj} is not an identity object
230 * @since Valhalla
231 */
232 @PreviewFeature(feature = PreviewFeature.Feature.VALUE_OBJECTS)
233 @ForceInline
234 public static <T> T requireIdentity(T obj) {
235 Objects.requireNonNull(obj);
236 if (!hasIdentity(obj))
237 throw new IdentityException(obj.getClass());
238 return obj;
239 }
240
241 /**
242 * Checks that the specified object reference is an identity object.
243 *
244 * @param obj the object reference to check for identity
245 * @param message detail message to be used in the event that an
246 * {@code IdentityException} is thrown; may be null
247 * @param <T> the type of the reference
248 * @return {@code obj} if {@code obj} is an identity object
249 * @throws NullPointerException if {@code obj} is {@code null}
250 * @throws IdentityException if {@code obj} is not an identity object
251 * @since Valhalla
252 */
253 @PreviewFeature(feature = PreviewFeature.Feature.VALUE_OBJECTS)
254 @ForceInline
255 public static <T> T requireIdentity(T obj, String message) {
256 Objects.requireNonNull(obj);
257 if (!hasIdentity(obj))
258 throw new IdentityException(message);
259 return obj;
260 }
261
262 /**
263 * Checks that the specified object reference is an identity object.
264 *
265 * @param obj the object reference to check for identity
266 * @param messageSupplier supplier of the detail message to be
267 * used in the event that an {@code IdentityException} is thrown; may be null
268 * @param <T> the type of the reference
269 * @return {@code obj} if {@code obj} is an identity object
270 * @throws NullPointerException if {@code obj} is {@code null}
271 * @throws IdentityException if {@code obj} is not an identity object
272 * @since Valhalla
273 */
274 @PreviewFeature(feature = PreviewFeature.Feature.VALUE_OBJECTS)
275 @ForceInline
276 public static <T> T requireIdentity(T obj, Supplier<String> messageSupplier) {
277 Objects.requireNonNull(obj);
278 if (!hasIdentity(obj))
279 throw new IdentityException(messageSupplier == null ?
280 null : messageSupplier.get());
281 return obj;
282 }
283
284 /**
285 * {@return 0 if the arguments are identical and {@code
286 * c.compare(a, b)} otherwise}
287 * Consequently, if both arguments are {@code null} 0
288 * is returned.
289 *
290 * <p>Note that if one of the arguments is {@code null}, a {@code
291 * NullPointerException} may or may not be thrown depending on
292 * what ordering policy, if any, the {@link Comparator Comparator}
293 * chooses to have for {@code null} values.
294 *
295 * @param <T> the type of the objects being compared
296 * @param a an object
297 * @param b an object to be compared with {@code a}
298 * @param c the {@code Comparator} to compare the first two arguments
299 * @see Comparable
300 * @see Comparator
301 */
302 public static <T> int compare(T a, T b, Comparator<? super T> c) {
303 return (a == b) ? 0 : c.compare(a, b);
304 }
305
306 /**
307 * Checks that the specified object reference is not {@code null}. This
308 * method is designed primarily for doing parameter validation in methods
309 * and constructors, as demonstrated below:
310 * <blockquote><pre>
311 * public Foo(Bar bar) {
312 * this.bar = Objects.requireNonNull(bar);
313 * }
314 * </pre></blockquote>
315 *
316 * @param obj the object reference to check for nullity
317 * @param <T> the type of the reference
318 * @return {@code obj} if not {@code null}
319 * @throws NullPointerException if {@code obj} is {@code null}
320 */
321 @ForceInline
322 public static <T> T requireNonNull(T obj) {
323 if (obj == null)
324 throw new NullPointerException();
325 return obj;
326 }
327
328 /**
329 * Checks that the specified object reference is not {@code null} and
330 * throws a customized {@link NullPointerException} if it is. This method
331 * is designed primarily for doing parameter validation in methods and
332 * constructors with multiple parameters, as demonstrated below:
333 * <blockquote><pre>
334 * public Foo(Bar bar, Baz baz) {
335 * this.bar = Objects.requireNonNull(bar, "bar must not be null");
336 * this.baz = Objects.requireNonNull(baz, "baz must not be null");
337 * }
338 * </pre></blockquote>
339 *
340 * @param obj the object reference to check for nullity
341 * @param message detail message to be used in the event that a {@code
342 * NullPointerException} is thrown
343 * @param <T> the type of the reference
344 * @return {@code obj} if not {@code null}
345 * @throws NullPointerException if {@code obj} is {@code null}
346 */
347 @ForceInline
348 public static <T> T requireNonNull(T obj, String message) {
349 if (obj == null)
350 throw new NullPointerException(message);
351 return obj;
352 }
353
354 /**
355 * {@return {@code true} if the provided reference is {@code
356 * null}; {@code false} otherwise}
357 *
358 * @apiNote This method exists to be used as a
359 * {@link java.util.function.Predicate}, {@code filter(Objects::isNull)}
360 *
361 * @param obj a reference to be checked against {@code null}
362 *
363 * @see java.util.function.Predicate
364 * @since 1.8
365 */
366 public static boolean isNull(Object obj) {
367 return obj == null;
368 }
369
370 /**
371 * {@return {@code true} if the provided reference is non-{@code null};
372 * {@code false} otherwise}
373 *
374 * @apiNote This method exists to be used as a
375 * {@link java.util.function.Predicate}, {@code filter(Objects::nonNull)}
376 *
377 * @param obj a reference to be checked against {@code null}
378 *
379 * @see java.util.function.Predicate
380 * @since 1.8
381 */
382 public static boolean nonNull(Object obj) {
383 return obj != null;
384 }
385
386 /**
387 * {@return the first argument if it is non-{@code null} and
388 * otherwise the second argument if it is non-{@code null}}
389 *
390 * @param obj an object
391 * @param defaultObj a non-{@code null} object to return if the first argument
392 * is {@code null}
393 * @param <T> the type of the reference
394 * @throws NullPointerException if both {@code obj} is null and
395 * {@code defaultObj} is {@code null}
396 * @since 9
397 */
398 public static <T> T requireNonNullElse(T obj, T defaultObj) {
399 return (obj != null) ? obj : requireNonNull(defaultObj, "defaultObj");
400 }
401
402 /**
403 * {@return the first argument if it is non-{@code null} and
404 * otherwise the value from {@code supplier.get()} if it is
405 * non-{@code null}}
406 *
407 * @param obj an object
408 * @param supplier of a non-{@code null} object to return if the first argument
409 * is {@code null}
410 * @param <T> the type of the first argument and return type
411 * @throws NullPointerException if both {@code obj} is null and
412 * either the {@code supplier} is {@code null} or
413 * the {@code supplier.get()} value is {@code null}
414 * @since 9
415 */
416 public static <T> T requireNonNullElseGet(T obj, Supplier<? extends T> supplier) {
417 return (obj != null) ? obj
418 : requireNonNull(requireNonNull(supplier, "supplier").get(), "supplier.get()");
419 }
420
421 /**
422 * Checks that the specified object reference is not {@code null} and
423 * throws a customized {@link NullPointerException} if it is.
424 *
425 * <p>Unlike the method {@link #requireNonNull(Object, String)},
426 * this method allows creation of the message to be deferred until
427 * after the null check is made. While this may confer a
428 * performance advantage in the non-null case, when deciding to
429 * call this method care should be taken that the costs of
430 * creating the message supplier are less than the cost of just
431 * creating the string message directly.
432 *
433 * @param obj the object reference to check for nullity
434 * @param messageSupplier supplier of the detail message to be
435 * used in the event that a {@code NullPointerException} is thrown
436 * @param <T> the type of the reference
437 * @return {@code obj} if not {@code null}
438 * @throws NullPointerException if {@code obj} is {@code null}
439 * @since 1.8
440 */
441 public static <T> T requireNonNull(T obj, Supplier<String> messageSupplier) {
442 if (obj == null)
443 throw new NullPointerException(messageSupplier == null ?
444 null : messageSupplier.get());
445 return obj;
446 }
447
448 /**
449 * Checks if the {@code index} is within the bounds of the range from
450 * {@code 0} (inclusive) to {@code length} (exclusive).
451 *
452 * <p>The {@code index} is defined to be out of bounds if any of the
453 * following inequalities is true:
454 * <ul>
455 * <li>{@code index < 0}</li>
456 * <li>{@code index >= length}</li>
457 * <li>{@code length < 0}, which is implied from the former inequalities</li>
458 * </ul>
459 *
460 * @param index the index
461 * @param length the upper-bound (exclusive) of the range
462 * @return {@code index} if it is within bounds of the range
463 * @throws IndexOutOfBoundsException if the {@code index} is out of bounds
464 * @since 9
465 */
466 @ForceInline
467 public static
468 int checkIndex(int index, int length) {
469 return Preconditions.checkIndex(index, length, null);
470 }
471
472 /**
473 * Checks if the sub-range from {@code fromIndex} (inclusive) to
474 * {@code toIndex} (exclusive) is within the bounds of range from {@code 0}
475 * (inclusive) to {@code length} (exclusive).
476 *
477 * <p>The sub-range is defined to be out of bounds if any of the following
478 * inequalities is true:
479 * <ul>
480 * <li>{@code fromIndex < 0}</li>
481 * <li>{@code fromIndex > toIndex}</li>
482 * <li>{@code toIndex > length}</li>
483 * <li>{@code length < 0}, which is implied from the former inequalities</li>
484 * </ul>
485 *
486 * @param fromIndex the lower-bound (inclusive) of the sub-range
487 * @param toIndex the upper-bound (exclusive) of the sub-range
488 * @param length the upper-bound (exclusive) the range
489 * @return {@code fromIndex} if the sub-range within bounds of the range
490 * @throws IndexOutOfBoundsException if the sub-range is out of bounds
491 * @since 9
492 */
493 public static
494 int checkFromToIndex(int fromIndex, int toIndex, int length) {
495 return Preconditions.checkFromToIndex(fromIndex, toIndex, length, null);
496 }
497
498 /**
499 * Checks if the sub-range from {@code fromIndex} (inclusive) to
500 * {@code fromIndex + size} (exclusive) is within the bounds of range from
501 * {@code 0} (inclusive) to {@code length} (exclusive).
502 *
503 * <p>The sub-range is defined to be out of bounds if any of the following
504 * inequalities is true:
505 * <ul>
506 * <li>{@code fromIndex < 0}</li>
507 * <li>{@code size < 0}</li>
508 * <li>{@code fromIndex + size > length}, taking into account integer overflow</li>
509 * <li>{@code length < 0}, which is implied from the former inequalities</li>
510 * </ul>
511 *
512 * @param fromIndex the lower-bound (inclusive) of the sub-interval
513 * @param size the size of the sub-range
514 * @param length the upper-bound (exclusive) of the range
515 * @return {@code fromIndex} if the sub-range within bounds of the range
516 * @throws IndexOutOfBoundsException if the sub-range is out of bounds
517 * @since 9
518 */
519 public static
520 int checkFromIndexSize(int fromIndex, int size, int length) {
521 return Preconditions.checkFromIndexSize(fromIndex, size, length, null);
522 }
523
524 /**
525 * Checks if the {@code index} is within the bounds of the range from
526 * {@code 0} (inclusive) to {@code length} (exclusive).
527 *
528 * <p>The {@code index} is defined to be out of bounds if any of the
529 * following inequalities is true:
530 * <ul>
531 * <li>{@code index < 0}</li>
532 * <li>{@code index >= length}</li>
533 * <li>{@code length < 0}, which is implied from the former inequalities</li>
534 * </ul>
535 *
536 * @param index the index
537 * @param length the upper-bound (exclusive) of the range
538 * @return {@code index} if it is within bounds of the range
539 * @throws IndexOutOfBoundsException if the {@code index} is out of bounds
540 * @since 16
541 */
542 @ForceInline
543 public static
544 long checkIndex(long index, long length) {
545 return Preconditions.checkIndex(index, length, null);
546 }
547
548 /**
549 * Checks if the sub-range from {@code fromIndex} (inclusive) to
550 * {@code toIndex} (exclusive) is within the bounds of range from {@code 0}
551 * (inclusive) to {@code length} (exclusive).
552 *
553 * <p>The sub-range is defined to be out of bounds if any of the following
554 * inequalities is true:
555 * <ul>
556 * <li>{@code fromIndex < 0}</li>
557 * <li>{@code fromIndex > toIndex}</li>
558 * <li>{@code toIndex > length}</li>
559 * <li>{@code length < 0}, which is implied from the former inequalities</li>
560 * </ul>
561 *
562 * @param fromIndex the lower-bound (inclusive) of the sub-range
563 * @param toIndex the upper-bound (exclusive) of the sub-range
564 * @param length the upper-bound (exclusive) the range
565 * @return {@code fromIndex} if the sub-range within bounds of the range
566 * @throws IndexOutOfBoundsException if the sub-range is out of bounds
567 * @since 16
568 */
569 public static
570 long checkFromToIndex(long fromIndex, long toIndex, long length) {
571 return Preconditions.checkFromToIndex(fromIndex, toIndex, length, null);
572 }
573
574 /**
575 * Checks if the sub-range from {@code fromIndex} (inclusive) to
576 * {@code fromIndex + size} (exclusive) is within the bounds of range from
577 * {@code 0} (inclusive) to {@code length} (exclusive).
578 *
579 * <p>The sub-range is defined to be out of bounds if any of the following
580 * inequalities is true:
581 * <ul>
582 * <li>{@code fromIndex < 0}</li>
583 * <li>{@code size < 0}</li>
584 * <li>{@code fromIndex + size > length}, taking into account integer overflow</li>
585 * <li>{@code length < 0}, which is implied from the former inequalities</li>
586 * </ul>
587 *
588 * @param fromIndex the lower-bound (inclusive) of the sub-interval
589 * @param size the size of the sub-range
590 * @param length the upper-bound (exclusive) of the range
591 * @return {@code fromIndex} if the sub-range within bounds of the range
592 * @throws IndexOutOfBoundsException if the sub-range is out of bounds
593 * @since 16
594 */
595 public static
596 long checkFromIndexSize(long fromIndex, long size, long length) {
597 return Preconditions.checkFromIndexSize(fromIndex, size, length, null);
598 }
599 }