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.misc.ValhallaFeatures;
29 import jdk.internal.util.Preconditions;
30 import jdk.internal.vm.annotation.ForceInline;
31 import jdk.internal.misc.Unsafe;
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 * Returns {@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 * @return {@code true} if the arguments are equal to each other
62 * and {@code false} otherwise
63 * @see Object#equals(Object)
64 */
65 public static boolean equals(Object a, Object b) {
66 return (a == b) || (a != null && a.equals(b));
67 }
68
69 /**
70 * Returns {@code true} if the arguments are deeply equal to each other
71 * and {@code false} otherwise.
72 *
73 * Two {@code null} values are deeply equal. If both arguments are
74 * arrays, the algorithm in {@link Arrays#deepEquals(Object[],
75 * Object[]) Arrays.deepEquals} is used to determine equality.
76 * Otherwise, equality is determined by using the {@link
77 * Object#equals equals} method of the first argument.
78 *
79 * @param a an object
80 * @param b an object to be compared with {@code a} for deep equality
81 * @return {@code true} if the arguments are deeply equal to each other
82 * and {@code false} otherwise
83 * @see Arrays#deepEquals(Object[], Object[])
84 * @see Objects#equals(Object, Object)
85 */
86 public static boolean deepEquals(Object a, Object b) {
87 if (a == b)
88 return true;
89 else if (a == null || b == null)
90 return false;
91 else
92 return Arrays.deepEquals0(a, b);
93 }
94
95 /**
96 * Returns the hash code of a non-{@code null} argument and 0 for
97 * a {@code null} argument.
98 *
99 * @param o an object
100 * @return the hash code of a non-{@code null} argument and 0 for
101 * a {@code null} argument
102 * @see Object#hashCode
103 */
104 public static int hashCode(Object o) {
105 return o != null ? o.hashCode() : 0;
106 }
107
108 /**
109 * Generates 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 * @return a hash value of the sequence of input values
131 * @see Arrays#hashCode(Object[])
132 * @see List#hashCode
133 */
134 public static int hash(Object... values) {
135 return Arrays.hashCode(values);
136 }
137
138 /**
139 * Returns the result of calling {@code toString} for a non-{@code
140 * null} argument and {@code "null"} for a {@code null} argument.
141 *
142 * @param o an object
143 * @return the result of calling {@code toString} for a non-{@code
144 * null} argument and {@code "null"} for a {@code null} argument
145 * @see Object#toString
146 * @see String#valueOf(Object)
147 */
148 public static String toString(Object o) {
149 return String.valueOf(o);
150 }
151
152 /**
153 * Returns the result of calling {@code toString} on the first
154 * argument if the first argument is not {@code null} and returns
155 * the second argument otherwise.
156 *
157 * @param o an object
158 * @param nullDefault string to return if the first argument is
159 * {@code null}
160 * @return the result of calling {@code toString} on the first
161 * argument if it is not {@code null} and the second argument
162 * otherwise.
163 * @see Objects#toString(Object)
164 */
165 public static String toString(Object o, String nullDefault) {
166 return (o != null) ? o.toString() : nullDefault;
167 }
168
169 /**
170 * {@return a string equivalent to the string returned by {@code
171 * Object.toString} if that method and {@code hashCode} are not
172 * overridden}
173 *
174 * @implNote
175 * This method constructs a string for an object without calling
176 * any overridable methods of the object.
177 *
178 * @implSpec
179 * The method returns a string equivalent to:<br>
180 * {@code o.getClass().getName() + "@" + Integer.toHexString(System.identityHashCode(o))}
181 *
182 * @param o an object
183 * @throws NullPointerException if the argument is null
184 * @see Object#toString
185 * @see System#identityHashCode(Object)
186 * @since 19
187 */
188 public static String toIdentityString(Object o) {
189 requireNonNull(o);
190 return o.getClass().getName() + "@" + Integer.toHexString(System.identityHashCode(o));
191 }
192
193 /**
194 * {@return {@code true} if the specified object reference is an identity object, otherwise {@code false}}
195 *
196 * @param obj an object
197 * @throws NullPointerException if {@code obj} is {@code null}
198 */
199 // @IntrinsicCandidate
200 public static boolean isIdentityObject(Object obj) {
201 requireNonNull(obj);
202 return obj.getClass().isIdentity() || // Before Valhalla all classes are identity classes
203 obj.getClass() == Object.class;
204 }
205
206 /**
207 * Checks that the specified object reference is an identity object.
208 *
209 * @param obj the object reference to check for identity
210 * @param <T> the type of the reference
211 * @return {@code obj} if {@code obj} is an identity object
212 * @throws NullPointerException if {@code obj} is {@code null}
213 * @throws IdentityException if {@code obj} is not an identity object
214 * @since Valhalla
215 */
216 @ForceInline
217 public static <T> T requireIdentity(T obj) {
218 Objects.requireNonNull(obj);
219 if (!isIdentityObject(obj))
220 throw new IdentityException(obj.getClass());
221 return obj;
222 }
223
224 /**
225 * Checks that the specified object reference is an identity object.
226 *
227 * @param obj the object reference to check for identity
228 * @param message detail message to be used in the event that an
229 * {@code IdentityException} is thrown; may be null
230 * @param <T> the type of the reference
231 * @return {@code obj} if {@code obj} is an identity object
232 * @throws NullPointerException if {@code obj} is {@code null}
233 * @throws IdentityException if {@code obj} is not an identity object
234 * @since Valhalla
235 */
236 @ForceInline
237 public static <T> T requireIdentity(T obj, String message) {
238 Objects.requireNonNull(obj);
239 if (!isIdentityObject(obj))
240 throw new IdentityException(message);
241 return obj;
242 }
243
244 /**
245 * Checks that the specified object reference is an identity object.
246 *
247 * @param obj the object reference to check for identity
248 * @param messageSupplier supplier of the detail message to be
249 * used in the event that an {@code IdentityException} is thrown; may be null
250 * @param <T> the type of the reference
251 * @return {@code obj} if {@code obj} is an identity object
252 * @throws NullPointerException if {@code obj} is {@code null}
253 * @throws IdentityException if {@code obj} is not an identity object
254 * @since Valhalla
255 */
256 @ForceInline
257 public static <T> T requireIdentity(T obj, Supplier<String> messageSupplier) {
258 Objects.requireNonNull(obj);
259 if (!isIdentityObject(obj))
260 throw new IdentityException(messageSupplier == null ?
261 null : messageSupplier.get());
262 return obj;
263 }
264
265 /**
266 * Returns 0 if the arguments are identical and {@code
267 * c.compare(a, b)} otherwise.
268 * Consequently, if both arguments are {@code null} 0
269 * is returned.
270 *
271 * <p>Note that if one of the arguments is {@code null}, a {@code
272 * NullPointerException} may or may not be thrown depending on
273 * what ordering policy, if any, the {@link Comparator Comparator}
274 * chooses to have for {@code null} values.
275 *
276 * @param <T> the type of the objects being compared
277 * @param a an object
278 * @param b an object to be compared with {@code a}
279 * @param c the {@code Comparator} to compare the first two arguments
280 * @return 0 if the arguments are identical and {@code
281 * c.compare(a, b)} otherwise.
282 * @see Comparable
283 * @see Comparator
284 */
285 public static <T> int compare(T a, T b, Comparator<? super T> c) {
286 return (a == b) ? 0 : c.compare(a, b);
287 }
288
289 /**
290 * Checks that the specified object reference is not {@code null}. This
291 * method is designed primarily for doing parameter validation in methods
292 * and constructors, as demonstrated below:
293 * <blockquote><pre>
294 * public Foo(Bar bar) {
295 * this.bar = Objects.requireNonNull(bar);
296 * }
297 * </pre></blockquote>
298 *
299 * @param obj the object reference to check for nullity
300 * @param <T> the type of the reference
301 * @return {@code obj} if not {@code null}
302 * @throws NullPointerException if {@code obj} is {@code null}
303 */
304 @ForceInline
305 public static <T> T requireNonNull(T obj) {
306 if (obj == null)
307 throw new NullPointerException();
308 return obj;
309 }
310
311 /**
312 * Checks that the specified object reference is not {@code null} and
313 * throws a customized {@link NullPointerException} if it is. This method
314 * is designed primarily for doing parameter validation in methods and
315 * constructors with multiple parameters, as demonstrated below:
316 * <blockquote><pre>
317 * public Foo(Bar bar, Baz baz) {
318 * this.bar = Objects.requireNonNull(bar, "bar must not be null");
319 * this.baz = Objects.requireNonNull(baz, "baz must not be null");
320 * }
321 * </pre></blockquote>
322 *
323 * @param obj the object reference to check for nullity
324 * @param message detail message to be used in the event that a {@code
325 * NullPointerException} is thrown
326 * @param <T> the type of the reference
327 * @return {@code obj} if not {@code null}
328 * @throws NullPointerException if {@code obj} is {@code null}
329 */
330 @ForceInline
331 public static <T> T requireNonNull(T obj, String message) {
332 if (obj == null)
333 throw new NullPointerException(message);
334 return obj;
335 }
336
337 /**
338 * Returns {@code true} if the provided reference is {@code null} otherwise
339 * returns {@code false}.
340 *
341 * @apiNote This method exists to be used as a
342 * {@link java.util.function.Predicate}, {@code filter(Objects::isNull)}
343 *
344 * @param obj a reference to be checked against {@code null}
345 * @return {@code true} if the provided reference is {@code null} otherwise
346 * {@code false}
347 *
348 * @see java.util.function.Predicate
349 * @since 1.8
350 */
351 public static boolean isNull(Object obj) {
352 return obj == null;
353 }
354
355 /**
356 * Returns {@code true} if the provided reference is non-{@code null}
357 * otherwise returns {@code false}.
358 *
359 * @apiNote This method exists to be used as a
360 * {@link java.util.function.Predicate}, {@code filter(Objects::nonNull)}
361 *
362 * @param obj a reference to be checked against {@code null}
363 * @return {@code true} if the provided reference is non-{@code null}
364 * otherwise {@code false}
365 *
366 * @see java.util.function.Predicate
367 * @since 1.8
368 */
369 public static boolean nonNull(Object obj) {
370 return obj != null;
371 }
372
373 /**
374 * Returns the first argument if it is non-{@code null} and
375 * otherwise returns the non-{@code null} second argument.
376 *
377 * @param obj an object
378 * @param defaultObj a non-{@code null} object to return if the first argument
379 * is {@code null}
380 * @param <T> the type of the reference
381 * @return the first argument if it is non-{@code null} and
382 * otherwise the second argument if it is non-{@code null}
383 * @throws NullPointerException if both {@code obj} is null and
384 * {@code defaultObj} is {@code null}
385 * @since 9
386 */
387 public static <T> T requireNonNullElse(T obj, T defaultObj) {
388 return (obj != null) ? obj : requireNonNull(defaultObj, "defaultObj");
389 }
390
391 /**
392 * Returns the first argument if it is non-{@code null} and otherwise
393 * returns the non-{@code null} value of {@code supplier.get()}.
394 *
395 * @param obj an object
396 * @param supplier of a non-{@code null} object to return if the first argument
397 * is {@code null}
398 * @param <T> the type of the first argument and return type
399 * @return the first argument if it is non-{@code null} and otherwise
400 * the value from {@code supplier.get()} if it is non-{@code null}
401 * @throws NullPointerException if both {@code obj} is null and
402 * either the {@code supplier} is {@code null} or
403 * the {@code supplier.get()} value is {@code null}
404 * @since 9
405 */
406 public static <T> T requireNonNullElseGet(T obj, Supplier<? extends T> supplier) {
407 return (obj != null) ? obj
408 : requireNonNull(requireNonNull(supplier, "supplier").get(), "supplier.get()");
409 }
410
411 /**
412 * Checks that the specified object reference is not {@code null} and
413 * throws a customized {@link NullPointerException} if it is.
414 *
415 * <p>Unlike the method {@link #requireNonNull(Object, String)},
416 * this method allows creation of the message to be deferred until
417 * after the null check is made. While this may confer a
418 * performance advantage in the non-null case, when deciding to
419 * call this method care should be taken that the costs of
420 * creating the message supplier are less than the cost of just
421 * creating the string message directly.
422 *
423 * @param obj the object reference to check for nullity
424 * @param messageSupplier supplier of the detail message to be
425 * used in the event that a {@code NullPointerException} is thrown
426 * @param <T> the type of the reference
427 * @return {@code obj} if not {@code null}
428 * @throws NullPointerException if {@code obj} is {@code null}
429 * @since 1.8
430 */
431 public static <T> T requireNonNull(T obj, Supplier<String> messageSupplier) {
432 if (obj == null)
433 throw new NullPointerException(messageSupplier == null ?
434 null : messageSupplier.get());
435 return obj;
436 }
437
438 /**
439 * Checks if the {@code index} is within the bounds of the range from
440 * {@code 0} (inclusive) to {@code length} (exclusive).
441 *
442 * <p>The {@code index} is defined to be out of bounds if any of the
443 * following inequalities is true:
444 * <ul>
445 * <li>{@code index < 0}</li>
446 * <li>{@code index >= length}</li>
447 * <li>{@code length < 0}, which is implied from the former inequalities</li>
448 * </ul>
449 *
450 * @param index the index
451 * @param length the upper-bound (exclusive) of the range
452 * @return {@code index} if it is within bounds of the range
453 * @throws IndexOutOfBoundsException if the {@code index} is out of bounds
454 * @since 9
455 */
456 @ForceInline
457 public static
458 int checkIndex(int index, int length) {
459 return Preconditions.checkIndex(index, length, null);
460 }
461
462 /**
463 * Checks if the sub-range from {@code fromIndex} (inclusive) to
464 * {@code toIndex} (exclusive) is within the bounds of range from {@code 0}
465 * (inclusive) to {@code length} (exclusive).
466 *
467 * <p>The sub-range is defined to be out of bounds if any of the following
468 * inequalities is true:
469 * <ul>
470 * <li>{@code fromIndex < 0}</li>
471 * <li>{@code fromIndex > toIndex}</li>
472 * <li>{@code toIndex > length}</li>
473 * <li>{@code length < 0}, which is implied from the former inequalities</li>
474 * </ul>
475 *
476 * @param fromIndex the lower-bound (inclusive) of the sub-range
477 * @param toIndex the upper-bound (exclusive) of the sub-range
478 * @param length the upper-bound (exclusive) the range
479 * @return {@code fromIndex} if the sub-range within bounds of the range
480 * @throws IndexOutOfBoundsException if the sub-range is out of bounds
481 * @since 9
482 */
483 public static
484 int checkFromToIndex(int fromIndex, int toIndex, int length) {
485 return Preconditions.checkFromToIndex(fromIndex, toIndex, length, null);
486 }
487
488 /**
489 * Checks if the sub-range from {@code fromIndex} (inclusive) to
490 * {@code fromIndex + size} (exclusive) is within the bounds of range from
491 * {@code 0} (inclusive) to {@code length} (exclusive).
492 *
493 * <p>The sub-range is defined to be out of bounds if any of the following
494 * inequalities is true:
495 * <ul>
496 * <li>{@code fromIndex < 0}</li>
497 * <li>{@code size < 0}</li>
498 * <li>{@code fromIndex + size > length}, taking into account integer overflow</li>
499 * <li>{@code length < 0}, which is implied from the former inequalities</li>
500 * </ul>
501 *
502 * @param fromIndex the lower-bound (inclusive) of the sub-interval
503 * @param size the size of the sub-range
504 * @param length the upper-bound (exclusive) of the range
505 * @return {@code fromIndex} if the sub-range within bounds of the range
506 * @throws IndexOutOfBoundsException if the sub-range is out of bounds
507 * @since 9
508 */
509 public static
510 int checkFromIndexSize(int fromIndex, int size, int length) {
511 return Preconditions.checkFromIndexSize(fromIndex, size, length, null);
512 }
513
514 /**
515 * Return the size of the object in the heap.
516 *
517 * @param o an object
518 * @return the objects's size
519 * @since Valhalla
520 */
521 public static long getObjectSize(Object o) {
522 return Unsafe.getUnsafe().getObjectSize(o);
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 }