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 @ForceInline
64 public static boolean equals(Object a, Object b) {
65 if (PreviewFeatures.isEnabled()) {
66 // With --enable-preview avoid acmp
67 return (a == null) ? b == null : a.equals(b);
68 } else {
69 return (a == b) || (a != null && a.equals(b));
70 }
71 }
72
73 /**
74 * {@return {@code true} if the arguments are deeply equal to each other
75 * and {@code false} otherwise}
76 *
77 * Two {@code null} values are deeply equal. If both arguments are
78 * arrays, the algorithm in {@link Arrays#deepEquals(Object[],
79 * Object[]) Arrays.deepEquals} is used to determine equality.
80 * Otherwise, equality is determined by using the {@link
81 * Object#equals equals} method of the first argument.
82 *
83 * @param a an object
84 * @param b an object to be compared with {@code a} for deep equality
85 * @see Arrays#deepEquals(Object[], Object[])
86 * @see Objects#equals(Object, Object)
87 */
88 public static boolean deepEquals(Object a, Object b) {
89 if (a == b)
90 return true;
91 else if (a == null || b == null)
92 return false;
93 else
94 return Arrays.deepEquals0(a, b);
95 }
96
97 /**
98 * {@return the hash code of a non-{@code null} argument and 0 for
99 * a {@code null} argument}
100 *
101 * @param o an object
102 * @see Object#hashCode
103 */
104 public static int hashCode(Object o) {
105 return o != null ? o.hashCode() : 0;
106 }
107
108 /**
109 * {@return a hash code for a sequence of input values} The hash
110 * code is generated as if all the input values were placed into an
111 * array, and that array were hashed by calling {@link
112 * Arrays#hashCode(Object[])}.
113 *
114 * <p>This method is useful for implementing {@link
115 * Object#hashCode()} on objects containing multiple fields. For
116 * example, if an object that has three fields, {@code x}, {@code
117 * y}, and {@code z}, one could write:
118 *
119 * <blockquote><pre>
120 * @Override public int hashCode() {
121 * return Objects.hash(x, y, z);
122 * }
123 * </pre></blockquote>
124 *
125 * <b>Warning: When a single object reference is supplied, the returned
126 * value does not equal the hash code of that object reference.</b> This
127 * value can be computed by calling {@link #hashCode(Object)}.
128 *
129 * @param values the values to be hashed
130 * @see Arrays#hashCode(Object[])
131 * @see List#hashCode
132 */
133 public static int hash(Object... values) {
134 return Arrays.hashCode(values);
135 }
136
137 /**
138 * {@return the result of calling {@code toString} for a
139 * non-{@code null} argument and {@code "null"} for a
140 * {@code null} argument}
141 *
142 * @param o an object
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 * {@return the result of calling {@code toString} on the first
152 * argument if the first argument is not {@code null} and the
153 * second argument otherwise}
154 *
155 * @param o an object
156 * @param nullDefault string to return if the first argument is
157 * {@code null}
158 * @see Objects#toString(Object)
159 */
160 public static String toString(Object o, String nullDefault) {
161 return (o != null) ? o.toString() : nullDefault;
162 }
163
164 /**
165 * {@return a string equivalent to the string returned by {@code
166 * Object.toString} if that method and {@code hashCode} are not
167 * overridden}
168 *
169 * @implNote
170 * This method constructs a string for an object without calling
171 * any overridable methods of the object.
172 *
173 * @implSpec
174 * The method returns a string equivalent to:<br>
175 * {@code o.getClass().getName() + "@" + Integer.toHexString(System.identityHashCode(o))}
176 *
177 * @param o an object
178 * @throws NullPointerException if the argument is null
179 * @see Object#toString
180 * @see System#identityHashCode(Object)
181 * @since 19
182 */
183 public static String toIdentityString(Object o) {
184 requireNonNull(o);
185 return o.getClass().getName() + "@" + Integer.toHexString(System.identityHashCode(o));
186 }
187
188 /**
189 * {@return {@code true} if the object is a non-null reference
190 * to an {@linkplain Class#isIdentity() identity object}, otherwise {@code false}}
191 *
192 * @apiNote
193 * If the parameter is {@code null}, there is no object
194 * and hence no class to check for identity; the return is {@code false}.
195 * To test for a {@linkplain Class#isValue() value object} use:
196 * {@snippet type="java" :
197 * if (obj != null && !Objects.hasIdentity(obj)) {
198 * // obj is a non-null value object
199 * }
200 * }
201 * @param obj an object or {@code null}
202 * @since Valhalla
203 */
204 @PreviewFeature(feature = PreviewFeature.Feature.VALUE_OBJECTS)
205 // @IntrinsicCandidate
206 public static boolean hasIdentity(Object obj) {
207 return (obj == null) ? false : obj.getClass().isIdentity();
208 }
209
210 /**
211 * {@return {@code true} if the object is a non-null reference
212 * to a {@linkplain Class#isValue() value object}, otherwise {@code false}}
213 *
214 * @param obj an object or {@code null}
215 * @since Valhalla
216 */
217 @PreviewFeature(feature = PreviewFeature.Feature.VALUE_OBJECTS)
218 // @IntrinsicCandidate
219 public static boolean isValueObject(Object obj) {
220 return (obj == null) ? false : obj.getClass().isValue();
221 }
222
223 /**
224 * Checks that the specified object reference is an identity object.
225 *
226 * @param obj the object reference to check for identity
227 * @param <T> the type of the reference
228 * @return {@code obj} if {@code obj} is an identity object
229 * @throws NullPointerException if {@code obj} is {@code null}
230 * @throws IdentityException if {@code obj} is not an identity object
231 * @since Valhalla
232 */
233 @PreviewFeature(feature = PreviewFeature.Feature.VALUE_OBJECTS)
234 @ForceInline
235 public static <T> T requireIdentity(T obj) {
236 Objects.requireNonNull(obj);
237 if (!hasIdentity(obj))
238 throw new IdentityException(obj.getClass());
239 return obj;
240 }
241
242 /**
243 * Checks that the specified object reference is an identity object.
244 *
245 * @param obj the object reference to check for identity
246 * @param message detail message to be used in the event that an
247 * {@code IdentityException} is thrown; may be null
248 * @param <T> the type of the reference
249 * @return {@code obj} if {@code obj} is an identity object
250 * @throws NullPointerException if {@code obj} is {@code null}
251 * @throws IdentityException if {@code obj} is not an identity object
252 * @since Valhalla
253 */
254 @PreviewFeature(feature = PreviewFeature.Feature.VALUE_OBJECTS)
255 @ForceInline
256 public static <T> T requireIdentity(T obj, String message) {
257 Objects.requireNonNull(obj);
258 if (!hasIdentity(obj))
259 throw new IdentityException(message);
260 return obj;
261 }
262
263 /**
264 * Checks that the specified object reference is an identity object.
265 *
266 * @param obj the object reference to check for identity
267 * @param messageSupplier supplier of the detail message to be
268 * used in the event that an {@code IdentityException} is thrown; may be null
269 * @param <T> the type of the reference
270 * @return {@code obj} if {@code obj} is an identity object
271 * @throws NullPointerException if {@code obj} is {@code null}
272 * @throws IdentityException if {@code obj} is not an identity object
273 * @since Valhalla
274 */
275 @PreviewFeature(feature = PreviewFeature.Feature.VALUE_OBJECTS)
276 @ForceInline
277 public static <T> T requireIdentity(T obj, Supplier<String> messageSupplier) {
278 Objects.requireNonNull(obj);
279 if (!hasIdentity(obj))
280 throw new IdentityException(messageSupplier == null ?
281 null : messageSupplier.get());
282 return obj;
283 }
284
285 /**
286 * {@return 0 if the arguments are identical and {@code
287 * c.compare(a, b)} otherwise}
288 * Consequently, if both arguments are {@code null} 0
289 * is returned.
290 *
291 * <p>Note that if one of the arguments is {@code null}, a {@code
292 * NullPointerException} may or may not be thrown depending on
293 * what ordering policy, if any, the {@link Comparator Comparator}
294 * chooses to have for {@code null} values.
295 *
296 * @param <T> the type of the objects being compared
297 * @param a an object
298 * @param b an object to be compared with {@code a}
299 * @param c the {@code Comparator} to compare the first two arguments
300 * @see Comparable
301 * @see Comparator
302 */
303 public static <T> int compare(T a, T b, Comparator<? super T> c) {
304 return (a == b) ? 0 : c.compare(a, b);
305 }
306
307 /**
308 * Checks that the specified object reference is not {@code null}. This
309 * method is designed primarily for doing parameter validation in methods
310 * and constructors, as demonstrated below:
311 * <blockquote><pre>
312 * public Foo(Bar bar) {
313 * this.bar = Objects.requireNonNull(bar);
314 * }
315 * </pre></blockquote>
316 *
317 * @param obj the object reference to check for nullity
318 * @param <T> the type of the reference
319 * @return {@code obj} if not {@code null}
320 * @throws NullPointerException if {@code obj} is {@code null}
321 */
322 @ForceInline
323 public static <T> T requireNonNull(T obj) {
324 if (obj == null)
325 throw new NullPointerException();
326 return obj;
327 }
328
329 /**
330 * Checks that the specified object reference is not {@code null} and
331 * throws a customized {@link NullPointerException} if it is. This method
332 * is designed primarily for doing parameter validation in methods and
333 * constructors with multiple parameters, as demonstrated below:
334 * <blockquote><pre>
335 * public Foo(Bar bar, Baz baz) {
336 * this.bar = Objects.requireNonNull(bar, "bar must not be null");
337 * this.baz = Objects.requireNonNull(baz, "baz must not be null");
338 * }
339 * </pre></blockquote>
340 *
341 * @param obj the object reference to check for nullity
342 * @param message detail message to be used in the event that a {@code
343 * NullPointerException} is thrown
344 * @param <T> the type of the reference
345 * @return {@code obj} if not {@code null}
346 * @throws NullPointerException if {@code obj} is {@code null}
347 */
348 @ForceInline
349 public static <T> T requireNonNull(T obj, String message) {
350 if (obj == null)
351 throw new NullPointerException(message);
352 return obj;
353 }
354
355 /**
356 * {@return {@code true} if the provided reference is {@code
357 * null}; {@code false} otherwise}
358 *
359 * @apiNote This method exists to be used as a
360 * {@link java.util.function.Predicate}, {@code filter(Objects::isNull)}
361 *
362 * @param obj a reference to be checked against {@code null}
363 *
364 * @see java.util.function.Predicate
365 * @since 1.8
366 */
367 public static boolean isNull(Object obj) {
368 return obj == null;
369 }
370
371 /**
372 * {@return {@code true} if the provided reference is non-{@code null};
373 * {@code false} otherwise}
374 *
375 * @apiNote This method exists to be used as a
376 * {@link java.util.function.Predicate}, {@code filter(Objects::nonNull)}
377 *
378 * @param obj a reference to be checked against {@code null}
379 *
380 * @see java.util.function.Predicate
381 * @since 1.8
382 */
383 public static boolean nonNull(Object obj) {
384 return obj != null;
385 }
386
387 /**
388 * {@return the first argument if it is non-{@code null} and
389 * otherwise the second argument if it is non-{@code null}}
390 *
391 * @param obj an object
392 * @param defaultObj a non-{@code null} object to return if the first argument
393 * is {@code null}
394 * @param <T> the type of the reference
395 * @throws NullPointerException if both {@code obj} is null and
396 * {@code defaultObj} is {@code null}
397 * @since 9
398 */
399 public static <T> T requireNonNullElse(T obj, T defaultObj) {
400 return (obj != null) ? obj : requireNonNull(defaultObj, "defaultObj");
401 }
402
403 /**
404 * {@return the first argument if it is non-{@code null} and
405 * otherwise the value from {@code supplier.get()} if it is
406 * non-{@code null}}
407 *
408 * @param obj an object
409 * @param supplier of a non-{@code null} object to return if the first argument
410 * is {@code null}
411 * @param <T> the type of the first argument and return type
412 * @throws NullPointerException if both {@code obj} is null and
413 * either the {@code supplier} is {@code null} or
414 * the {@code supplier.get()} value is {@code null}
415 * @since 9
416 */
417 public static <T> T requireNonNullElseGet(T obj, Supplier<? extends T> supplier) {
418 return (obj != null) ? obj
419 : requireNonNull(requireNonNull(supplier, "supplier").get(), "supplier.get()");
420 }
421
422 /**
423 * Checks that the specified object reference is not {@code null} and
424 * throws a customized {@link NullPointerException} if it is.
425 *
426 * <p>Unlike the method {@link #requireNonNull(Object, String)},
427 * this method allows creation of the message to be deferred until
428 * after the null check is made. While this may confer a
429 * performance advantage in the non-null case, when deciding to
430 * call this method care should be taken that the costs of
431 * creating the message supplier are less than the cost of just
432 * creating the string message directly.
433 *
434 * @param obj the object reference to check for nullity
435 * @param messageSupplier supplier of the detail message to be
436 * used in the event that a {@code NullPointerException} is thrown
437 * @param <T> the type of the reference
438 * @return {@code obj} if not {@code null}
439 * @throws NullPointerException if {@code obj} is {@code null}
440 * @since 1.8
441 */
442 public static <T> T requireNonNull(T obj, Supplier<String> messageSupplier) {
443 if (obj == null)
444 throw new NullPointerException(messageSupplier == null ?
445 null : messageSupplier.get());
446 return obj;
447 }
448
449 /**
450 * Checks if the {@code index} is within the bounds of the range from
451 * {@code 0} (inclusive) to {@code length} (exclusive).
452 *
453 * <p>The {@code index} is defined to be out of bounds if any of the
454 * following inequalities is true:
455 * <ul>
456 * <li>{@code index < 0}</li>
457 * <li>{@code index >= length}</li>
458 * <li>{@code length < 0}, which is implied from the former inequalities</li>
459 * </ul>
460 *
461 * @param index the index
462 * @param length the upper-bound (exclusive) of the range
463 * @return {@code index} if it is within bounds of the range
464 * @throws IndexOutOfBoundsException if the {@code index} is out of bounds
465 * @since 9
466 */
467 @ForceInline
468 public static
469 int checkIndex(int index, int length) {
470 return Preconditions.checkIndex(index, length, null);
471 }
472
473 /**
474 * Checks if the sub-range from {@code fromIndex} (inclusive) to
475 * {@code toIndex} (exclusive) is within the bounds of range from {@code 0}
476 * (inclusive) to {@code length} (exclusive).
477 *
478 * <p>The sub-range is defined to be out of bounds if any of the following
479 * inequalities is true:
480 * <ul>
481 * <li>{@code fromIndex < 0}</li>
482 * <li>{@code fromIndex > toIndex}</li>
483 * <li>{@code toIndex > length}</li>
484 * <li>{@code length < 0}, which is implied from the former inequalities</li>
485 * </ul>
486 *
487 * @param fromIndex the lower-bound (inclusive) of the sub-range
488 * @param toIndex the upper-bound (exclusive) of the sub-range
489 * @param length the upper-bound (exclusive) the range
490 * @return {@code fromIndex} if the sub-range within bounds of the range
491 * @throws IndexOutOfBoundsException if the sub-range is out of bounds
492 * @since 9
493 */
494 public static
495 int checkFromToIndex(int fromIndex, int toIndex, int length) {
496 return Preconditions.checkFromToIndex(fromIndex, toIndex, length, null);
497 }
498
499 /**
500 * Checks if the sub-range from {@code fromIndex} (inclusive) to
501 * {@code fromIndex + size} (exclusive) is within the bounds of range from
502 * {@code 0} (inclusive) to {@code length} (exclusive).
503 *
504 * <p>The sub-range is defined to be out of bounds if any of the following
505 * inequalities is true:
506 * <ul>
507 * <li>{@code fromIndex < 0}</li>
508 * <li>{@code size < 0}</li>
509 * <li>{@code fromIndex + size > length}, taking into account integer overflow</li>
510 * <li>{@code length < 0}, which is implied from the former inequalities</li>
511 * </ul>
512 *
513 * @param fromIndex the lower-bound (inclusive) of the sub-interval
514 * @param size the size of the sub-range
515 * @param length the upper-bound (exclusive) of the range
516 * @return {@code fromIndex} if the sub-range within bounds of the range
517 * @throws IndexOutOfBoundsException if the sub-range is out of bounds
518 * @since 9
519 */
520 public static
521 int checkFromIndexSize(int fromIndex, int size, int length) {
522 return Preconditions.checkFromIndexSize(fromIndex, size, length, null);
523 }
524
525 /**
526 * Checks if the {@code index} is within the bounds of the range from
527 * {@code 0} (inclusive) to {@code length} (exclusive).
528 *
529 * <p>The {@code index} is defined to be out of bounds if any of the
530 * following inequalities is true:
531 * <ul>
532 * <li>{@code index < 0}</li>
533 * <li>{@code index >= length}</li>
534 * <li>{@code length < 0}, which is implied from the former inequalities</li>
535 * </ul>
536 *
537 * @param index the index
538 * @param length the upper-bound (exclusive) of the range
539 * @return {@code index} if it is within bounds of the range
540 * @throws IndexOutOfBoundsException if the {@code index} is out of bounds
541 * @since 16
542 */
543 @ForceInline
544 public static
545 long checkIndex(long index, long length) {
546 return Preconditions.checkIndex(index, length, null);
547 }
548
549 /**
550 * Checks if the sub-range from {@code fromIndex} (inclusive) to
551 * {@code toIndex} (exclusive) is within the bounds of range from {@code 0}
552 * (inclusive) to {@code length} (exclusive).
553 *
554 * <p>The sub-range is defined to be out of bounds if any of the following
555 * inequalities is true:
556 * <ul>
557 * <li>{@code fromIndex < 0}</li>
558 * <li>{@code fromIndex > toIndex}</li>
559 * <li>{@code toIndex > length}</li>
560 * <li>{@code length < 0}, which is implied from the former inequalities</li>
561 * </ul>
562 *
563 * @param fromIndex the lower-bound (inclusive) of the sub-range
564 * @param toIndex the upper-bound (exclusive) of the sub-range
565 * @param length the upper-bound (exclusive) the range
566 * @return {@code fromIndex} if the sub-range within bounds of the range
567 * @throws IndexOutOfBoundsException if the sub-range is out of bounds
568 * @since 16
569 */
570 public static
571 long checkFromToIndex(long fromIndex, long toIndex, long length) {
572 return Preconditions.checkFromToIndex(fromIndex, toIndex, length, null);
573 }
574
575 /**
576 * Checks if the sub-range from {@code fromIndex} (inclusive) to
577 * {@code fromIndex + size} (exclusive) is within the bounds of range from
578 * {@code 0} (inclusive) to {@code length} (exclusive).
579 *
580 * <p>The sub-range is defined to be out of bounds if any of the following
581 * inequalities is true:
582 * <ul>
583 * <li>{@code fromIndex < 0}</li>
584 * <li>{@code size < 0}</li>
585 * <li>{@code fromIndex + size > length}, taking into account integer overflow</li>
586 * <li>{@code length < 0}, which is implied from the former inequalities</li>
587 * </ul>
588 *
589 * @param fromIndex the lower-bound (inclusive) of the sub-interval
590 * @param size the size of the sub-range
591 * @param length the upper-bound (exclusive) of the range
592 * @return {@code fromIndex} if the sub-range within bounds of the range
593 * @throws IndexOutOfBoundsException if the sub-range is out of bounds
594 * @since 16
595 */
596 public static
597 long checkFromIndexSize(long fromIndex, long size, long length) {
598 return Preconditions.checkFromIndexSize(fromIndex, size, length, null);
599 }
600 }