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.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 * 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,
195 * otherwise {@code false}}
196 *
197 * @param obj an object
198 * @throws NullPointerException if {@code obj} is {@code null}
199 */
200 @PreviewFeature(feature = PreviewFeature.Feature.VALUE_OBJECTS)
201 // @IntrinsicCandidate
202 public static boolean isIdentityObject(Object obj) {
203 requireNonNull(obj);
204 return obj.getClass().isIdentity() || // Before Valhalla all classes are identity classes
205 obj.getClass() == Object.class;
206 }
207
208 /**
209 * Checks that the specified object reference is an identity object.
210 *
211 * @param obj the object reference to check for identity
212 * @param <T> the type of the reference
213 * @return {@code obj} if {@code obj} is an identity object
214 * @throws NullPointerException if {@code obj} is {@code null}
215 * @throws IdentityException if {@code obj} is not an identity object
216 * @since Valhalla
217 */
218 @PreviewFeature(feature = PreviewFeature.Feature.VALUE_OBJECTS)
219 @ForceInline
220 public static <T> T requireIdentity(T obj) {
221 Objects.requireNonNull(obj);
222 if (!isIdentityObject(obj))
223 throw new IdentityException(obj.getClass());
224 return obj;
225 }
226
227 /**
228 * Checks that the specified object reference is an identity object.
229 *
230 * @param obj the object reference to check for identity
231 * @param message detail message to be used in the event that an
232 * {@code IdentityException} is thrown; may be null
233 * @param <T> the type of the reference
234 * @return {@code obj} if {@code obj} is an identity object
235 * @throws NullPointerException if {@code obj} is {@code null}
236 * @throws IdentityException if {@code obj} is not an identity object
237 * @since Valhalla
238 */
239 @PreviewFeature(feature = PreviewFeature.Feature.VALUE_OBJECTS)
240 @ForceInline
241 public static <T> T requireIdentity(T obj, String message) {
242 Objects.requireNonNull(obj);
243 if (!isIdentityObject(obj))
244 throw new IdentityException(message);
245 return obj;
246 }
247
248 /**
249 * Checks that the specified object reference is an identity object.
250 *
251 * @param obj the object reference to check for identity
252 * @param messageSupplier supplier of the detail message to be
253 * used in the event that an {@code IdentityException} is thrown; may be null
254 * @param <T> the type of the reference
255 * @return {@code obj} if {@code obj} is an identity object
256 * @throws NullPointerException if {@code obj} is {@code null}
257 * @throws IdentityException if {@code obj} is not an identity object
258 * @since Valhalla
259 */
260 @PreviewFeature(feature = PreviewFeature.Feature.VALUE_OBJECTS)
261 @ForceInline
262 public static <T> T requireIdentity(T obj, Supplier<String> messageSupplier) {
263 Objects.requireNonNull(obj);
264 if (!isIdentityObject(obj))
265 throw new IdentityException(messageSupplier == null ?
266 null : messageSupplier.get());
267 return obj;
268 }
269
270 /**
271 * {@return {@code true} if the specified object is a {@linkplain Class#isValue value object},
272 * otherwise {@code false}}
273 *
274 * @param obj an object
275 * @throws NullPointerException if {@code obj} is {@code null}
276 */
277 @PreviewFeature(feature = PreviewFeature.Feature.VALUE_OBJECTS)
278 // @IntrinsicCandidate
279 public static boolean isValueObject(Object obj) {
280 requireNonNull(obj, "obj");
281 return obj.getClass().isValue();
282 }
283
284 /**
285 * Returns 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 * @return 0 if the arguments are identical and {@code
300 * c.compare(a, b)} otherwise.
301 * @see Comparable
302 * @see Comparator
303 */
304 public static <T> int compare(T a, T b, Comparator<? super T> c) {
305 return (a == b) ? 0 : c.compare(a, b);
306 }
307
308 /**
309 * Checks that the specified object reference is not {@code null}. This
310 * method is designed primarily for doing parameter validation in methods
311 * and constructors, as demonstrated below:
312 * <blockquote><pre>
313 * public Foo(Bar bar) {
314 * this.bar = Objects.requireNonNull(bar);
315 * }
316 * </pre></blockquote>
317 *
318 * @param obj the object reference to check for nullity
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) {
325 if (obj == null)
326 throw new NullPointerException();
327 return obj;
328 }
329
330 /**
331 * Checks that the specified object reference is not {@code null} and
332 * throws a customized {@link NullPointerException} if it is. This method
333 * is designed primarily for doing parameter validation in methods and
334 * constructors with multiple parameters, as demonstrated below:
335 * <blockquote><pre>
336 * public Foo(Bar bar, Baz baz) {
337 * this.bar = Objects.requireNonNull(bar, "bar must not be null");
338 * this.baz = Objects.requireNonNull(baz, "baz must not be null");
339 * }
340 * </pre></blockquote>
341 *
342 * @param obj the object reference to check for nullity
343 * @param message detail message to be used in the event that a {@code
344 * NullPointerException} is thrown
345 * @param <T> the type of the reference
346 * @return {@code obj} if not {@code null}
347 * @throws NullPointerException if {@code obj} is {@code null}
348 */
349 @ForceInline
350 public static <T> T requireNonNull(T obj, String message) {
351 if (obj == null)
352 throw new NullPointerException(message);
353 return obj;
354 }
355
356 /**
357 * Returns {@code true} if the provided reference is {@code null} otherwise
358 * returns {@code false}.
359 *
360 * @apiNote This method exists to be used as a
361 * {@link java.util.function.Predicate}, {@code filter(Objects::isNull)}
362 *
363 * @param obj a reference to be checked against {@code null}
364 * @return {@code true} if the provided reference is {@code null} otherwise
365 * {@code false}
366 *
367 * @see java.util.function.Predicate
368 * @since 1.8
369 */
370 public static boolean isNull(Object obj) {
371 return obj == null;
372 }
373
374 /**
375 * Returns {@code true} if the provided reference is non-{@code null}
376 * otherwise returns {@code false}.
377 *
378 * @apiNote This method exists to be used as a
379 * {@link java.util.function.Predicate}, {@code filter(Objects::nonNull)}
380 *
381 * @param obj a reference to be checked against {@code null}
382 * @return {@code true} if the provided reference is non-{@code null}
383 * otherwise {@code false}
384 *
385 * @see java.util.function.Predicate
386 * @since 1.8
387 */
388 public static boolean nonNull(Object obj) {
389 return obj != null;
390 }
391
392 /**
393 * Returns the first argument if it is non-{@code null} and
394 * otherwise returns the non-{@code null} second argument.
395 *
396 * @param obj an object
397 * @param defaultObj a non-{@code null} object to return if the first argument
398 * is {@code null}
399 * @param <T> the type of the reference
400 * @return the first argument if it is non-{@code null} and
401 * otherwise the second argument if it is non-{@code null}
402 * @throws NullPointerException if both {@code obj} is null and
403 * {@code defaultObj} is {@code null}
404 * @since 9
405 */
406 public static <T> T requireNonNullElse(T obj, T defaultObj) {
407 return (obj != null) ? obj : requireNonNull(defaultObj, "defaultObj");
408 }
409
410 /**
411 * Returns the first argument if it is non-{@code null} and otherwise
412 * returns the non-{@code null} value of {@code supplier.get()}.
413 *
414 * @param obj an object
415 * @param supplier of a non-{@code null} object to return if the first argument
416 * is {@code null}
417 * @param <T> the type of the first argument and return type
418 * @return the first argument if it is non-{@code null} and otherwise
419 * the value from {@code supplier.get()} if it is non-{@code null}
420 * @throws NullPointerException if both {@code obj} is null and
421 * either the {@code supplier} is {@code null} or
422 * the {@code supplier.get()} value is {@code null}
423 * @since 9
424 */
425 public static <T> T requireNonNullElseGet(T obj, Supplier<? extends T> supplier) {
426 return (obj != null) ? obj
427 : requireNonNull(requireNonNull(supplier, "supplier").get(), "supplier.get()");
428 }
429
430 /**
431 * Checks that the specified object reference is not {@code null} and
432 * throws a customized {@link NullPointerException} if it is.
433 *
434 * <p>Unlike the method {@link #requireNonNull(Object, String)},
435 * this method allows creation of the message to be deferred until
436 * after the null check is made. While this may confer a
437 * performance advantage in the non-null case, when deciding to
438 * call this method care should be taken that the costs of
439 * creating the message supplier are less than the cost of just
440 * creating the string message directly.
441 *
442 * @param obj the object reference to check for nullity
443 * @param messageSupplier supplier of the detail message to be
444 * used in the event that a {@code NullPointerException} is thrown
445 * @param <T> the type of the reference
446 * @return {@code obj} if not {@code null}
447 * @throws NullPointerException if {@code obj} is {@code null}
448 * @since 1.8
449 */
450 public static <T> T requireNonNull(T obj, Supplier<String> messageSupplier) {
451 if (obj == null)
452 throw new NullPointerException(messageSupplier == null ?
453 null : messageSupplier.get());
454 return obj;
455 }
456
457 /**
458 * Checks if the {@code index} is within the bounds of the range from
459 * {@code 0} (inclusive) to {@code length} (exclusive).
460 *
461 * <p>The {@code index} is defined to be out of bounds if any of the
462 * following inequalities is true:
463 * <ul>
464 * <li>{@code index < 0}</li>
465 * <li>{@code index >= length}</li>
466 * <li>{@code length < 0}, which is implied from the former inequalities</li>
467 * </ul>
468 *
469 * @param index the index
470 * @param length the upper-bound (exclusive) of the range
471 * @return {@code index} if it is within bounds of the range
472 * @throws IndexOutOfBoundsException if the {@code index} is out of bounds
473 * @since 9
474 */
475 @ForceInline
476 public static
477 int checkIndex(int index, int length) {
478 return Preconditions.checkIndex(index, length, null);
479 }
480
481 /**
482 * Checks if the sub-range from {@code fromIndex} (inclusive) to
483 * {@code toIndex} (exclusive) is within the bounds of range from {@code 0}
484 * (inclusive) to {@code length} (exclusive).
485 *
486 * <p>The sub-range is defined to be out of bounds if any of the following
487 * inequalities is true:
488 * <ul>
489 * <li>{@code fromIndex < 0}</li>
490 * <li>{@code fromIndex > toIndex}</li>
491 * <li>{@code toIndex > length}</li>
492 * <li>{@code length < 0}, which is implied from the former inequalities</li>
493 * </ul>
494 *
495 * @param fromIndex the lower-bound (inclusive) of the sub-range
496 * @param toIndex the upper-bound (exclusive) of the sub-range
497 * @param length the upper-bound (exclusive) the range
498 * @return {@code fromIndex} if the sub-range within bounds of the range
499 * @throws IndexOutOfBoundsException if the sub-range is out of bounds
500 * @since 9
501 */
502 public static
503 int checkFromToIndex(int fromIndex, int toIndex, int length) {
504 return Preconditions.checkFromToIndex(fromIndex, toIndex, length, null);
505 }
506
507 /**
508 * Checks if the sub-range from {@code fromIndex} (inclusive) to
509 * {@code fromIndex + size} (exclusive) is within the bounds of range from
510 * {@code 0} (inclusive) to {@code length} (exclusive).
511 *
512 * <p>The sub-range is defined to be out of bounds if any of the following
513 * inequalities is true:
514 * <ul>
515 * <li>{@code fromIndex < 0}</li>
516 * <li>{@code size < 0}</li>
517 * <li>{@code fromIndex + size > length}, taking into account integer overflow</li>
518 * <li>{@code length < 0}, which is implied from the former inequalities</li>
519 * </ul>
520 *
521 * @param fromIndex the lower-bound (inclusive) of the sub-interval
522 * @param size the size of the sub-range
523 * @param length the upper-bound (exclusive) of the range
524 * @return {@code fromIndex} if the sub-range within bounds of the range
525 * @throws IndexOutOfBoundsException if the sub-range is out of bounds
526 * @since 9
527 */
528 public static
529 int checkFromIndexSize(int fromIndex, int size, int length) {
530 return Preconditions.checkFromIndexSize(fromIndex, size, length, null);
531 }
532
533 /**
534 * Return the size of the object in the heap.
535 *
536 * @param o an object
537 * @return the objects's size
538 * @since Valhalla
539 */
540 public static long getObjectSize(Object o) {
541 return Unsafe.getUnsafe().getObjectSize(o);
542 }
543
544 /**
545 * Checks if the {@code index} is within the bounds of the range from
546 * {@code 0} (inclusive) to {@code length} (exclusive).
547 *
548 * <p>The {@code index} is defined to be out of bounds if any of the
549 * following inequalities is true:
550 * <ul>
551 * <li>{@code index < 0}</li>
552 * <li>{@code index >= length}</li>
553 * <li>{@code length < 0}, which is implied from the former inequalities</li>
554 * </ul>
555 *
556 * @param index the index
557 * @param length the upper-bound (exclusive) of the range
558 * @return {@code index} if it is within bounds of the range
559 * @throws IndexOutOfBoundsException if the {@code index} is out of bounds
560 * @since 16
561 */
562 @ForceInline
563 public static
564 long checkIndex(long index, long length) {
565 return Preconditions.checkIndex(index, length, null);
566 }
567
568 /**
569 * Checks if the sub-range from {@code fromIndex} (inclusive) to
570 * {@code toIndex} (exclusive) is within the bounds of range from {@code 0}
571 * (inclusive) to {@code length} (exclusive).
572 *
573 * <p>The sub-range is defined to be out of bounds if any of the following
574 * inequalities is true:
575 * <ul>
576 * <li>{@code fromIndex < 0}</li>
577 * <li>{@code fromIndex > toIndex}</li>
578 * <li>{@code toIndex > length}</li>
579 * <li>{@code length < 0}, which is implied from the former inequalities</li>
580 * </ul>
581 *
582 * @param fromIndex the lower-bound (inclusive) of the sub-range
583 * @param toIndex the upper-bound (exclusive) of the sub-range
584 * @param length the upper-bound (exclusive) the range
585 * @return {@code fromIndex} if the sub-range within bounds of the range
586 * @throws IndexOutOfBoundsException if the sub-range is out of bounds
587 * @since 16
588 */
589 public static
590 long checkFromToIndex(long fromIndex, long toIndex, long length) {
591 return Preconditions.checkFromToIndex(fromIndex, toIndex, length, null);
592 }
593
594 /**
595 * Checks if the sub-range from {@code fromIndex} (inclusive) to
596 * {@code fromIndex + size} (exclusive) is within the bounds of range from
597 * {@code 0} (inclusive) to {@code length} (exclusive).
598 *
599 * <p>The sub-range is defined to be out of bounds if any of the following
600 * inequalities is true:
601 * <ul>
602 * <li>{@code fromIndex < 0}</li>
603 * <li>{@code size < 0}</li>
604 * <li>{@code fromIndex + size > length}, taking into account integer overflow</li>
605 * <li>{@code length < 0}, which is implied from the former inequalities</li>
606 * </ul>
607 *
608 * @param fromIndex the lower-bound (inclusive) of the sub-interval
609 * @param size the size of the sub-range
610 * @param length the upper-bound (exclusive) of the range
611 * @return {@code fromIndex} if the sub-range within bounds of the range
612 * @throws IndexOutOfBoundsException if the sub-range is out of bounds
613 * @since 16
614 */
615 public static
616 long checkFromIndexSize(long fromIndex, long size, long length) {
617 return Preconditions.checkFromIndexSize(fromIndex, size, length, null);
618 }
619 }