1 /*
2 * Copyright (c) 2009, 2023, 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.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 * {@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 return (a == b) || (a != null && a.equals(b));
65 }
66
67 /**
68 * {@return {@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 * @see Arrays#deepEquals(Object[], Object[])
80 * @see Objects#equals(Object, Object)
81 */
82 public static boolean deepEquals(Object a, Object b) {
83 if (a == b)
84 return true;
85 else if (a == null || b == null)
86 return false;
87 else
88 return Arrays.deepEquals0(a, b);
89 }
90
91 /**
92 * {@return the hash code of a non-{@code null} argument and 0 for
93 * a {@code null} argument}
94 *
95 * @param o an object
96 * @see Object#hashCode
97 */
98 public static int hashCode(Object o) {
99 return o != null ? o.hashCode() : 0;
100 }
101
102 /**
103 * {@return a hash code for a sequence of input values} The hash
104 * code is generated as if all the input values were placed into an
105 * array, and that array were hashed by calling {@link
106 * Arrays#hashCode(Object[])}.
107 *
108 * <p>This method is useful for implementing {@link
109 * Object#hashCode()} on objects containing multiple fields. For
110 * example, if an object that has three fields, {@code x}, {@code
111 * y}, and {@code z}, one could write:
112 *
113 * <blockquote><pre>
114 * @Override public int hashCode() {
115 * return Objects.hash(x, y, z);
116 * }
117 * </pre></blockquote>
118 *
119 * <b>Warning: When a single object reference is supplied, the returned
120 * value does not equal the hash code of that object reference.</b> This
121 * value can be computed by calling {@link #hashCode(Object)}.
122 *
123 * @param values the values to be hashed
124 * @see Arrays#hashCode(Object[])
125 * @see List#hashCode
126 */
127 public static int hash(Object... values) {
128 return Arrays.hashCode(values);
129 }
130
131 /**
132 * {@return the result of calling {@code toString} for a
133 * non-{@code null} argument and {@code "null"} for a
134 * {@code null} argument}
135 *
136 * @param o an object
137 * @see Object#toString
138 * @see String#valueOf(Object)
139 */
140 public static String toString(Object o) {
141 return String.valueOf(o);
142 }
143
144 /**
145 * {@return the result of calling {@code toString} on the first
146 * argument if the first argument is not {@code null} and the
147 * second argument otherwise}
148 *
149 * @param o an object
150 * @param nullDefault string to return if the first argument is
151 * {@code null}
152 * @see Objects#toString(Object)
153 */
154 public static String toString(Object o, String nullDefault) {
155 return (o != null) ? o.toString() : nullDefault;
156 }
157
158 /**
159 * {@return a string equivalent to the string returned by {@code
160 * Object.toString} if that method and {@code hashCode} are not
161 * overridden}
162 *
163 * @implNote
164 * This method constructs a string for an object without calling
165 * any overridable methods of the object.
166 *
167 * @implSpec
168 * The method returns a string equivalent to:<br>
169 * {@code o.getClass().getName() + "@" + Integer.toHexString(System.identityHashCode(o))}
170 *
171 * @param o an object
172 * @throws NullPointerException if the argument is null
173 * @see Object#toString
174 * @see System#identityHashCode(Object)
175 * @since 19
176 */
177 public static String toIdentityString(Object o) {
178 requireNonNull(o);
179 return o.getClass().getName() + "@" + Integer.toHexString(System.identityHashCode(o));
180 }
181
182 /**
183 * {@return {@code true} if the specified object reference is an identity object,
184 * otherwise {@code false}}
185 *
186 * @param obj an object
187 * @throws NullPointerException if {@code obj} is {@code null}
188 * @since Valhalla
189 */
190 @PreviewFeature(feature = PreviewFeature.Feature.VALUE_OBJECTS)
191 // @IntrinsicCandidate
192 public static boolean hasIdentity(Object obj) {
193 requireNonNull(obj);
194 return obj.getClass().isIdentity() || // Before Valhalla all classes are identity classes
195 obj.getClass() == Object.class;
196 }
197
198 /**
199 * Checks that the specified object reference is an identity object.
200 *
201 * @param obj the object reference to check for identity
202 * @param <T> the type of the reference
203 * @return {@code obj} if {@code obj} is an identity object
204 * @throws NullPointerException if {@code obj} is {@code null}
205 * @throws IdentityException if {@code obj} is not an identity object
206 * @since Valhalla
207 */
208 @PreviewFeature(feature = PreviewFeature.Feature.VALUE_OBJECTS)
209 @ForceInline
210 public static <T> T requireIdentity(T obj) {
211 Objects.requireNonNull(obj);
212 if (!hasIdentity(obj))
213 throw new IdentityException(obj.getClass());
214 return obj;
215 }
216
217 /**
218 * Checks that the specified object reference is an identity object.
219 *
220 * @param obj the object reference to check for identity
221 * @param message detail message to be used in the event that an
222 * {@code IdentityException} is thrown; may be null
223 * @param <T> the type of the reference
224 * @return {@code obj} if {@code obj} is an identity object
225 * @throws NullPointerException if {@code obj} is {@code null}
226 * @throws IdentityException if {@code obj} is not an identity object
227 * @since Valhalla
228 */
229 @PreviewFeature(feature = PreviewFeature.Feature.VALUE_OBJECTS)
230 @ForceInline
231 public static <T> T requireIdentity(T obj, String message) {
232 Objects.requireNonNull(obj);
233 if (!hasIdentity(obj))
234 throw new IdentityException(message);
235 return obj;
236 }
237
238 /**
239 * Checks that the specified object reference is an identity object.
240 *
241 * @param obj the object reference to check for identity
242 * @param messageSupplier supplier of the detail message to be
243 * used in the event that an {@code IdentityException} is thrown; may be null
244 * @param <T> the type of the reference
245 * @return {@code obj} if {@code obj} is an identity object
246 * @throws NullPointerException if {@code obj} is {@code null}
247 * @throws IdentityException if {@code obj} is not an identity object
248 * @since Valhalla
249 */
250 @PreviewFeature(feature = PreviewFeature.Feature.VALUE_OBJECTS)
251 @ForceInline
252 public static <T> T requireIdentity(T obj, Supplier<String> messageSupplier) {
253 Objects.requireNonNull(obj);
254 if (!hasIdentity(obj))
255 throw new IdentityException(messageSupplier == null ?
256 null : messageSupplier.get());
257 return obj;
258 }
259
260 /**
261 * {@return 0 if the arguments are identical and {@code
262 * c.compare(a, b)} otherwise}
263 * Consequently, if both arguments are {@code null} 0
264 * is returned.
265 *
266 * <p>Note that if one of the arguments is {@code null}, a {@code
267 * NullPointerException} may or may not be thrown depending on
268 * what ordering policy, if any, the {@link Comparator Comparator}
269 * chooses to have for {@code null} values.
270 *
271 * @param <T> the type of the objects being compared
272 * @param a an object
273 * @param b an object to be compared with {@code a}
274 * @param c the {@code Comparator} to compare the first two arguments
275 * @see Comparable
276 * @see Comparator
277 */
278 public static <T> int compare(T a, T b, Comparator<? super T> c) {
279 return (a == b) ? 0 : c.compare(a, b);
280 }
281
282 /**
283 * Checks that the specified object reference is not {@code null}. This
284 * method is designed primarily for doing parameter validation in methods
285 * and constructors, as demonstrated below:
286 * <blockquote><pre>
287 * public Foo(Bar bar) {
288 * this.bar = Objects.requireNonNull(bar);
289 * }
290 * </pre></blockquote>
291 *
292 * @param obj the object reference to check for nullity
293 * @param <T> the type of the reference
294 * @return {@code obj} if not {@code null}
295 * @throws NullPointerException if {@code obj} is {@code null}
296 */
297 @ForceInline
298 public static <T> T requireNonNull(T obj) {
299 if (obj == null)
300 throw new NullPointerException();
301 return obj;
302 }
303
304 /**
305 * Checks that the specified object reference is not {@code null} and
306 * throws a customized {@link NullPointerException} if it is. This method
307 * is designed primarily for doing parameter validation in methods and
308 * constructors with multiple parameters, as demonstrated below:
309 * <blockquote><pre>
310 * public Foo(Bar bar, Baz baz) {
311 * this.bar = Objects.requireNonNull(bar, "bar must not be null");
312 * this.baz = Objects.requireNonNull(baz, "baz must not be null");
313 * }
314 * </pre></blockquote>
315 *
316 * @param obj the object reference to check for nullity
317 * @param message detail message to be used in the event that a {@code
318 * NullPointerException} is thrown
319 * @param <T> the type of the reference
320 * @return {@code obj} if not {@code null}
321 * @throws NullPointerException if {@code obj} is {@code null}
322 */
323 @ForceInline
324 public static <T> T requireNonNull(T obj, String message) {
325 if (obj == null)
326 throw new NullPointerException(message);
327 return obj;
328 }
329
330 /**
331 * {@return {@code true} if the provided reference is {@code
332 * null}; {@code false} otherwise}
333 *
334 * @apiNote This method exists to be used as a
335 * {@link java.util.function.Predicate}, {@code filter(Objects::isNull)}
336 *
337 * @param obj a reference to be checked against {@code null}
338 *
339 * @see java.util.function.Predicate
340 * @since 1.8
341 */
342 public static boolean isNull(Object obj) {
343 return obj == null;
344 }
345
346 /**
347 * {@return {@code true} if the provided reference is non-{@code null};
348 * {@code false} otherwise}
349 *
350 * @apiNote This method exists to be used as a
351 * {@link java.util.function.Predicate}, {@code filter(Objects::nonNull)}
352 *
353 * @param obj a reference to be checked against {@code null}
354 *
355 * @see java.util.function.Predicate
356 * @since 1.8
357 */
358 public static boolean nonNull(Object obj) {
359 return obj != null;
360 }
361
362 /**
363 * {@return the first argument if it is non-{@code null} and
364 * otherwise the second argument if it is non-{@code null}}
365 *
366 * @param obj an object
367 * @param defaultObj a non-{@code null} object to return if the first argument
368 * is {@code null}
369 * @param <T> the type of the reference
370 * @throws NullPointerException if both {@code obj} is null and
371 * {@code defaultObj} is {@code null}
372 * @since 9
373 */
374 public static <T> T requireNonNullElse(T obj, T defaultObj) {
375 return (obj != null) ? obj : requireNonNull(defaultObj, "defaultObj");
376 }
377
378 /**
379 * {@return the first argument if it is non-{@code null} and
380 * otherwise the value from {@code supplier.get()} if it is
381 * non-{@code null}}
382 *
383 * @param obj an object
384 * @param supplier of a non-{@code null} object to return if the first argument
385 * is {@code null}
386 * @param <T> the type of the first argument and return type
387 * @throws NullPointerException if both {@code obj} is null and
388 * either the {@code supplier} is {@code null} or
389 * the {@code supplier.get()} value is {@code null}
390 * @since 9
391 */
392 public static <T> T requireNonNullElseGet(T obj, Supplier<? extends T> supplier) {
393 return (obj != null) ? obj
394 : requireNonNull(requireNonNull(supplier, "supplier").get(), "supplier.get()");
395 }
396
397 /**
398 * Checks that the specified object reference is not {@code null} and
399 * throws a customized {@link NullPointerException} if it is.
400 *
401 * <p>Unlike the method {@link #requireNonNull(Object, String)},
402 * this method allows creation of the message to be deferred until
403 * after the null check is made. While this may confer a
404 * performance advantage in the non-null case, when deciding to
405 * call this method care should be taken that the costs of
406 * creating the message supplier are less than the cost of just
407 * creating the string message directly.
408 *
409 * @param obj the object reference to check for nullity
410 * @param messageSupplier supplier of the detail message to be
411 * used in the event that a {@code NullPointerException} is thrown
412 * @param <T> the type of the reference
413 * @return {@code obj} if not {@code null}
414 * @throws NullPointerException if {@code obj} is {@code null}
415 * @since 1.8
416 */
417 public static <T> T requireNonNull(T obj, Supplier<String> messageSupplier) {
418 if (obj == null)
419 throw new NullPointerException(messageSupplier == null ?
420 null : messageSupplier.get());
421 return obj;
422 }
423
424 /**
425 * Checks if the {@code index} is within the bounds of the range from
426 * {@code 0} (inclusive) to {@code length} (exclusive).
427 *
428 * <p>The {@code index} is defined to be out of bounds if any of the
429 * following inequalities is true:
430 * <ul>
431 * <li>{@code index < 0}</li>
432 * <li>{@code index >= length}</li>
433 * <li>{@code length < 0}, which is implied from the former inequalities</li>
434 * </ul>
435 *
436 * @param index the index
437 * @param length the upper-bound (exclusive) of the range
438 * @return {@code index} if it is within bounds of the range
439 * @throws IndexOutOfBoundsException if the {@code index} is out of bounds
440 * @since 9
441 */
442 @ForceInline
443 public static
444 int checkIndex(int index, int length) {
445 return Preconditions.checkIndex(index, length, null);
446 }
447
448 /**
449 * Checks if the sub-range from {@code fromIndex} (inclusive) to
450 * {@code toIndex} (exclusive) is within the bounds of range from {@code 0}
451 * (inclusive) to {@code length} (exclusive).
452 *
453 * <p>The sub-range is defined to be out of bounds if any of the following
454 * inequalities is true:
455 * <ul>
456 * <li>{@code fromIndex < 0}</li>
457 * <li>{@code fromIndex > toIndex}</li>
458 * <li>{@code toIndex > length}</li>
459 * <li>{@code length < 0}, which is implied from the former inequalities</li>
460 * </ul>
461 *
462 * @param fromIndex the lower-bound (inclusive) of the sub-range
463 * @param toIndex the upper-bound (exclusive) of the sub-range
464 * @param length the upper-bound (exclusive) the range
465 * @return {@code fromIndex} if the sub-range within bounds of the range
466 * @throws IndexOutOfBoundsException if the sub-range is out of bounds
467 * @since 9
468 */
469 public static
470 int checkFromToIndex(int fromIndex, int toIndex, int length) {
471 return Preconditions.checkFromToIndex(fromIndex, toIndex, length, null);
472 }
473
474 /**
475 * Checks if the sub-range from {@code fromIndex} (inclusive) to
476 * {@code fromIndex + size} (exclusive) is within the bounds of range from
477 * {@code 0} (inclusive) to {@code length} (exclusive).
478 *
479 * <p>The sub-range is defined to be out of bounds if any of the following
480 * inequalities is true:
481 * <ul>
482 * <li>{@code fromIndex < 0}</li>
483 * <li>{@code size < 0}</li>
484 * <li>{@code fromIndex + size > length}, taking into account integer overflow</li>
485 * <li>{@code length < 0}, which is implied from the former inequalities</li>
486 * </ul>
487 *
488 * @param fromIndex the lower-bound (inclusive) of the sub-interval
489 * @param size the size of the sub-range
490 * @param length the upper-bound (exclusive) of the range
491 * @return {@code fromIndex} if the sub-range within bounds of the range
492 * @throws IndexOutOfBoundsException if the sub-range is out of bounds
493 * @since 9
494 */
495 public static
496 int checkFromIndexSize(int fromIndex, int size, int length) {
497 return Preconditions.checkFromIndexSize(fromIndex, size, length, null);
498 }
499
500 /**
501 * Checks if the {@code index} is within the bounds of the range from
502 * {@code 0} (inclusive) to {@code length} (exclusive).
503 *
504 * <p>The {@code index} is defined to be out of bounds if any of the
505 * following inequalities is true:
506 * <ul>
507 * <li>{@code index < 0}</li>
508 * <li>{@code index >= length}</li>
509 * <li>{@code length < 0}, which is implied from the former inequalities</li>
510 * </ul>
511 *
512 * @param index the index
513 * @param length the upper-bound (exclusive) of the range
514 * @return {@code index} if it is within bounds of the range
515 * @throws IndexOutOfBoundsException if the {@code index} is out of bounds
516 * @since 16
517 */
518 @ForceInline
519 public static
520 long checkIndex(long index, long length) {
521 return Preconditions.checkIndex(index, length, null);
522 }
523
524 /**
525 * Checks if the sub-range from {@code fromIndex} (inclusive) to
526 * {@code toIndex} (exclusive) is within the bounds of range from {@code 0}
527 * (inclusive) to {@code length} (exclusive).
528 *
529 * <p>The sub-range is defined to be out of bounds if any of the following
530 * inequalities is true:
531 * <ul>
532 * <li>{@code fromIndex < 0}</li>
533 * <li>{@code fromIndex > toIndex}</li>
534 * <li>{@code toIndex > length}</li>
535 * <li>{@code length < 0}, which is implied from the former inequalities</li>
536 * </ul>
537 *
538 * @param fromIndex the lower-bound (inclusive) of the sub-range
539 * @param toIndex the upper-bound (exclusive) of the sub-range
540 * @param length the upper-bound (exclusive) the range
541 * @return {@code fromIndex} if the sub-range within bounds of the range
542 * @throws IndexOutOfBoundsException if the sub-range is out of bounds
543 * @since 16
544 */
545 public static
546 long checkFromToIndex(long fromIndex, long toIndex, long length) {
547 return Preconditions.checkFromToIndex(fromIndex, toIndex, length, null);
548 }
549
550 /**
551 * Checks if the sub-range from {@code fromIndex} (inclusive) to
552 * {@code fromIndex + size} (exclusive) is within the bounds of range from
553 * {@code 0} (inclusive) to {@code length} (exclusive).
554 *
555 * <p>The sub-range is defined to be out of bounds if any of the following
556 * inequalities is true:
557 * <ul>
558 * <li>{@code fromIndex < 0}</li>
559 * <li>{@code size < 0}</li>
560 * <li>{@code fromIndex + size > length}, taking into account integer overflow</li>
561 * <li>{@code length < 0}, which is implied from the former inequalities</li>
562 * </ul>
563 *
564 * @param fromIndex the lower-bound (inclusive) of the sub-interval
565 * @param size the size of the sub-range
566 * @param length the upper-bound (exclusive) of the range
567 * @return {@code fromIndex} if the sub-range within bounds of the range
568 * @throws IndexOutOfBoundsException if the sub-range is out of bounds
569 * @since 16
570 */
571 public static
572 long checkFromIndexSize(long fromIndex, long size, long length) {
573 return Preconditions.checkFromIndexSize(fromIndex, size, length, null);
574 }
575 }