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 */
189 @PreviewFeature(feature = PreviewFeature.Feature.VALUE_OBJECTS)
190 // @IntrinsicCandidate
191 public static boolean isIdentityObject(Object obj) {
192 requireNonNull(obj);
193 return obj.getClass().isIdentity() || // Before Valhalla all classes are identity classes
194 obj.getClass() == Object.class;
195 }
196
197 /**
198 * Checks that the specified object reference is an identity object.
199 *
200 * @param obj the object reference to check for identity
201 * @param <T> the type of the reference
202 * @return {@code obj} if {@code obj} is an identity object
203 * @throws NullPointerException if {@code obj} is {@code null}
204 * @throws IdentityException if {@code obj} is not an identity object
205 * @since Valhalla
206 */
207 @PreviewFeature(feature = PreviewFeature.Feature.VALUE_OBJECTS)
208 @ForceInline
209 public static <T> T requireIdentity(T obj) {
210 Objects.requireNonNull(obj);
211 if (!isIdentityObject(obj))
212 throw new IdentityException(obj.getClass());
213 return obj;
214 }
215
216 /**
217 * Checks that the specified object reference is an identity object.
218 *
219 * @param obj the object reference to check for identity
220 * @param message detail message to be used in the event that an
221 * {@code IdentityException} is thrown; may be null
222 * @param <T> the type of the reference
223 * @return {@code obj} if {@code obj} is an identity object
224 * @throws NullPointerException if {@code obj} is {@code null}
225 * @throws IdentityException if {@code obj} is not an identity object
226 * @since Valhalla
227 */
228 @PreviewFeature(feature = PreviewFeature.Feature.VALUE_OBJECTS)
229 @ForceInline
230 public static <T> T requireIdentity(T obj, String message) {
231 Objects.requireNonNull(obj);
232 if (!isIdentityObject(obj))
233 throw new IdentityException(message);
234 return obj;
235 }
236
237 /**
238 * Checks that the specified object reference is an identity object.
239 *
240 * @param obj the object reference to check for identity
241 * @param messageSupplier supplier of the detail message to be
242 * used in the event that an {@code IdentityException} is thrown; may be null
243 * @param <T> the type of the reference
244 * @return {@code obj} if {@code obj} is an identity object
245 * @throws NullPointerException if {@code obj} is {@code null}
246 * @throws IdentityException if {@code obj} is not an identity object
247 * @since Valhalla
248 */
249 @PreviewFeature(feature = PreviewFeature.Feature.VALUE_OBJECTS)
250 @ForceInline
251 public static <T> T requireIdentity(T obj, Supplier<String> messageSupplier) {
252 Objects.requireNonNull(obj);
253 if (!isIdentityObject(obj))
254 throw new IdentityException(messageSupplier == null ?
255 null : messageSupplier.get());
256 return obj;
257 }
258
259 /**
260 * {@return {@code true} if the specified object is a {@linkplain Class#isValue value object},
261 * otherwise {@code false}}
262 *
263 * @param obj an object
264 * @throws NullPointerException if {@code obj} is {@code null}
265 */
266 @PreviewFeature(feature = PreviewFeature.Feature.VALUE_OBJECTS)
267 // @IntrinsicCandidate
268 public static boolean isValueObject(Object obj) {
269 requireNonNull(obj, "obj");
270 return obj.getClass().isValue();
271 }
272
273 /**
274 * {@return 0 if the arguments are identical and {@code
275 * c.compare(a, b)} otherwise}
276 * Consequently, if both arguments are {@code null} 0
277 * is returned.
278 *
279 * <p>Note that if one of the arguments is {@code null}, a {@code
280 * NullPointerException} may or may not be thrown depending on
281 * what ordering policy, if any, the {@link Comparator Comparator}
282 * chooses to have for {@code null} values.
283 *
284 * @param <T> the type of the objects being compared
285 * @param a an object
286 * @param b an object to be compared with {@code a}
287 * @param c the {@code Comparator} to compare the first two arguments
288 * @see Comparable
289 * @see Comparator
290 */
291 public static <T> int compare(T a, T b, Comparator<? super T> c) {
292 return (a == b) ? 0 : c.compare(a, b);
293 }
294
295 /**
296 * Checks that the specified object reference is not {@code null}. This
297 * method is designed primarily for doing parameter validation in methods
298 * and constructors, as demonstrated below:
299 * <blockquote><pre>
300 * public Foo(Bar bar) {
301 * this.bar = Objects.requireNonNull(bar);
302 * }
303 * </pre></blockquote>
304 *
305 * @param obj the object reference to check for nullity
306 * @param <T> the type of the reference
307 * @return {@code obj} if not {@code null}
308 * @throws NullPointerException if {@code obj} is {@code null}
309 */
310 @ForceInline
311 public static <T> T requireNonNull(T obj) {
312 if (obj == null)
313 throw new NullPointerException();
314 return obj;
315 }
316
317 /**
318 * Checks that the specified object reference is not {@code null} and
319 * throws a customized {@link NullPointerException} if it is. This method
320 * is designed primarily for doing parameter validation in methods and
321 * constructors with multiple parameters, as demonstrated below:
322 * <blockquote><pre>
323 * public Foo(Bar bar, Baz baz) {
324 * this.bar = Objects.requireNonNull(bar, "bar must not be null");
325 * this.baz = Objects.requireNonNull(baz, "baz must not be null");
326 * }
327 * </pre></blockquote>
328 *
329 * @param obj the object reference to check for nullity
330 * @param message detail message to be used in the event that a {@code
331 * NullPointerException} is thrown
332 * @param <T> the type of the reference
333 * @return {@code obj} if not {@code null}
334 * @throws NullPointerException if {@code obj} is {@code null}
335 */
336 @ForceInline
337 public static <T> T requireNonNull(T obj, String message) {
338 if (obj == null)
339 throw new NullPointerException(message);
340 return obj;
341 }
342
343 /**
344 * {@return {@code true} if the provided reference is {@code
345 * null}; {@code false} otherwise}
346 *
347 * @apiNote This method exists to be used as a
348 * {@link java.util.function.Predicate}, {@code filter(Objects::isNull)}
349 *
350 * @param obj a reference to be checked against {@code null}
351 *
352 * @see java.util.function.Predicate
353 * @since 1.8
354 */
355 public static boolean isNull(Object obj) {
356 return obj == null;
357 }
358
359 /**
360 * {@return {@code true} if the provided reference is non-{@code null};
361 * {@code false} otherwise}
362 *
363 * @apiNote This method exists to be used as a
364 * {@link java.util.function.Predicate}, {@code filter(Objects::nonNull)}
365 *
366 * @param obj a reference to be checked against {@code null}
367 *
368 * @see java.util.function.Predicate
369 * @since 1.8
370 */
371 public static boolean nonNull(Object obj) {
372 return obj != null;
373 }
374
375 /**
376 * {@return the first argument if it is non-{@code null} and
377 * otherwise the second argument if it is non-{@code null}}
378 *
379 * @param obj an object
380 * @param defaultObj a non-{@code null} object to return if the first argument
381 * is {@code null}
382 * @param <T> the type of the reference
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 * {@return the first argument if it is non-{@code null} and
393 * otherwise the value from {@code supplier.get()} if it is
394 * non-{@code null}}
395 *
396 * @param obj an object
397 * @param supplier of a non-{@code null} object to return if the first argument
398 * is {@code null}
399 * @param <T> the type of the first argument and return type
400 * @throws NullPointerException if both {@code obj} is null and
401 * either the {@code supplier} is {@code null} or
402 * the {@code supplier.get()} value is {@code null}
403 * @since 9
404 */
405 public static <T> T requireNonNullElseGet(T obj, Supplier<? extends T> supplier) {
406 return (obj != null) ? obj
407 : requireNonNull(requireNonNull(supplier, "supplier").get(), "supplier.get()");
408 }
409
410 /**
411 * Checks that the specified object reference is not {@code null} and
412 * throws a customized {@link NullPointerException} if it is.
413 *
414 * <p>Unlike the method {@link #requireNonNull(Object, String)},
415 * this method allows creation of the message to be deferred until
416 * after the null check is made. While this may confer a
417 * performance advantage in the non-null case, when deciding to
418 * call this method care should be taken that the costs of
419 * creating the message supplier are less than the cost of just
420 * creating the string message directly.
421 *
422 * @param obj the object reference to check for nullity
423 * @param messageSupplier supplier of the detail message to be
424 * used in the event that a {@code NullPointerException} is thrown
425 * @param <T> the type of the reference
426 * @return {@code obj} if not {@code null}
427 * @throws NullPointerException if {@code obj} is {@code null}
428 * @since 1.8
429 */
430 public static <T> T requireNonNull(T obj, Supplier<String> messageSupplier) {
431 if (obj == null)
432 throw new NullPointerException(messageSupplier == null ?
433 null : messageSupplier.get());
434 return obj;
435 }
436
437 /**
438 * Checks if the {@code index} is within the bounds of the range from
439 * {@code 0} (inclusive) to {@code length} (exclusive).
440 *
441 * <p>The {@code index} is defined to be out of bounds if any of the
442 * following inequalities is true:
443 * <ul>
444 * <li>{@code index < 0}</li>
445 * <li>{@code index >= length}</li>
446 * <li>{@code length < 0}, which is implied from the former inequalities</li>
447 * </ul>
448 *
449 * @param index the index
450 * @param length the upper-bound (exclusive) of the range
451 * @return {@code index} if it is within bounds of the range
452 * @throws IndexOutOfBoundsException if the {@code index} is out of bounds
453 * @since 9
454 */
455 @ForceInline
456 public static
457 int checkIndex(int index, int length) {
458 return Preconditions.checkIndex(index, length, null);
459 }
460
461 /**
462 * Checks if the sub-range from {@code fromIndex} (inclusive) to
463 * {@code toIndex} (exclusive) is within the bounds of range from {@code 0}
464 * (inclusive) to {@code length} (exclusive).
465 *
466 * <p>The sub-range is defined to be out of bounds if any of the following
467 * inequalities is true:
468 * <ul>
469 * <li>{@code fromIndex < 0}</li>
470 * <li>{@code fromIndex > toIndex}</li>
471 * <li>{@code toIndex > length}</li>
472 * <li>{@code length < 0}, which is implied from the former inequalities</li>
473 * </ul>
474 *
475 * @param fromIndex the lower-bound (inclusive) of the sub-range
476 * @param toIndex the upper-bound (exclusive) of the sub-range
477 * @param length the upper-bound (exclusive) the range
478 * @return {@code fromIndex} if the sub-range within bounds of the range
479 * @throws IndexOutOfBoundsException if the sub-range is out of bounds
480 * @since 9
481 */
482 public static
483 int checkFromToIndex(int fromIndex, int toIndex, int length) {
484 return Preconditions.checkFromToIndex(fromIndex, toIndex, length, null);
485 }
486
487 /**
488 * Checks if the sub-range from {@code fromIndex} (inclusive) to
489 * {@code fromIndex + size} (exclusive) is within the bounds of range from
490 * {@code 0} (inclusive) to {@code length} (exclusive).
491 *
492 * <p>The sub-range is defined to be out of bounds if any of the following
493 * inequalities is true:
494 * <ul>
495 * <li>{@code fromIndex < 0}</li>
496 * <li>{@code size < 0}</li>
497 * <li>{@code fromIndex + size > length}, taking into account integer overflow</li>
498 * <li>{@code length < 0}, which is implied from the former inequalities</li>
499 * </ul>
500 *
501 * @param fromIndex the lower-bound (inclusive) of the sub-interval
502 * @param size the size of the sub-range
503 * @param length the upper-bound (exclusive) of the range
504 * @return {@code fromIndex} if the sub-range within bounds of the range
505 * @throws IndexOutOfBoundsException if the sub-range is out of bounds
506 * @since 9
507 */
508 public static
509 int checkFromIndexSize(int fromIndex, int size, int length) {
510 return Preconditions.checkFromIndexSize(fromIndex, size, length, null);
511 }
512
513 /**
514 * Return the size of the object in the heap.
515 *
516 * @param o an object
517 * @return the objects's size
518 * @since Valhalla
519 */
520 public static long getObjectSize(Object o) {
521 return Unsafe.getUnsafe().getObjectSize(o);
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 }