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 hasIdentity(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 (!hasIdentity(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 (!hasIdentity(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 (!hasIdentity(obj))
254 throw new IdentityException(messageSupplier == null ?
255 null : messageSupplier.get());
256 return obj;
257 }
258
259 /**
260 * {@return 0 if the arguments are identical and {@code
261 * c.compare(a, b)} otherwise}
262 * Consequently, if both arguments are {@code null} 0
263 * is returned.
264 *
265 * <p>Note that if one of the arguments is {@code null}, a {@code
266 * NullPointerException} may or may not be thrown depending on
267 * what ordering policy, if any, the {@link Comparator Comparator}
268 * chooses to have for {@code null} values.
269 *
270 * @param <T> the type of the objects being compared
271 * @param a an object
272 * @param b an object to be compared with {@code a}
273 * @param c the {@code Comparator} to compare the first two arguments
274 * @see Comparable
275 * @see Comparator
276 */
277 public static <T> int compare(T a, T b, Comparator<? super T> c) {
278 return (a == b) ? 0 : c.compare(a, b);
279 }
280
281 /**
282 * Checks that the specified object reference is not {@code null}. This
283 * method is designed primarily for doing parameter validation in methods
284 * and constructors, as demonstrated below:
285 * <blockquote><pre>
286 * public Foo(Bar bar) {
287 * this.bar = Objects.requireNonNull(bar);
288 * }
289 * </pre></blockquote>
290 *
291 * @param obj the object reference to check for nullity
292 * @param <T> the type of the reference
293 * @return {@code obj} if not {@code null}
294 * @throws NullPointerException if {@code obj} is {@code null}
295 */
296 @ForceInline
297 public static <T> T requireNonNull(T obj) {
298 if (obj == null)
299 throw new NullPointerException();
300 return obj;
301 }
302
303 /**
304 * Checks that the specified object reference is not {@code null} and
305 * throws a customized {@link NullPointerException} if it is. This method
306 * is designed primarily for doing parameter validation in methods and
307 * constructors with multiple parameters, as demonstrated below:
308 * <blockquote><pre>
309 * public Foo(Bar bar, Baz baz) {
310 * this.bar = Objects.requireNonNull(bar, "bar must not be null");
311 * this.baz = Objects.requireNonNull(baz, "baz must not be null");
312 * }
313 * </pre></blockquote>
314 *
315 * @param obj the object reference to check for nullity
316 * @param message detail message to be used in the event that a {@code
317 * NullPointerException} is thrown
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, String message) {
324 if (obj == null)
325 throw new NullPointerException(message);
326 return obj;
327 }
328
329 /**
330 * {@return {@code true} if the provided reference is {@code
331 * null}; {@code false} otherwise}
332 *
333 * @apiNote This method exists to be used as a
334 * {@link java.util.function.Predicate}, {@code filter(Objects::isNull)}
335 *
336 * @param obj a reference to be checked against {@code null}
337 *
338 * @see java.util.function.Predicate
339 * @since 1.8
340 */
341 public static boolean isNull(Object obj) {
342 return obj == null;
343 }
344
345 /**
346 * {@return {@code true} if the provided reference is non-{@code null};
347 * {@code false} otherwise}
348 *
349 * @apiNote This method exists to be used as a
350 * {@link java.util.function.Predicate}, {@code filter(Objects::nonNull)}
351 *
352 * @param obj a reference to be checked against {@code null}
353 *
354 * @see java.util.function.Predicate
355 * @since 1.8
356 */
357 public static boolean nonNull(Object obj) {
358 return obj != null;
359 }
360
361 /**
362 * {@return the first argument if it is non-{@code null} and
363 * otherwise the second argument if it is non-{@code null}}
364 *
365 * @param obj an object
366 * @param defaultObj a non-{@code null} object to return if the first argument
367 * is {@code null}
368 * @param <T> the type of the reference
369 * @throws NullPointerException if both {@code obj} is null and
370 * {@code defaultObj} is {@code null}
371 * @since 9
372 */
373 public static <T> T requireNonNullElse(T obj, T defaultObj) {
374 return (obj != null) ? obj : requireNonNull(defaultObj, "defaultObj");
375 }
376
377 /**
378 * {@return the first argument if it is non-{@code null} and
379 * otherwise the value from {@code supplier.get()} if it is
380 * non-{@code null}}
381 *
382 * @param obj an object
383 * @param supplier of a non-{@code null} object to return if the first argument
384 * is {@code null}
385 * @param <T> the type of the first argument and return type
386 * @throws NullPointerException if both {@code obj} is null and
387 * either the {@code supplier} is {@code null} or
388 * the {@code supplier.get()} value is {@code null}
389 * @since 9
390 */
391 public static <T> T requireNonNullElseGet(T obj, Supplier<? extends T> supplier) {
392 return (obj != null) ? obj
393 : requireNonNull(requireNonNull(supplier, "supplier").get(), "supplier.get()");
394 }
395
396 /**
397 * Checks that the specified object reference is not {@code null} and
398 * throws a customized {@link NullPointerException} if it is.
399 *
400 * <p>Unlike the method {@link #requireNonNull(Object, String)},
401 * this method allows creation of the message to be deferred until
402 * after the null check is made. While this may confer a
403 * performance advantage in the non-null case, when deciding to
404 * call this method care should be taken that the costs of
405 * creating the message supplier are less than the cost of just
406 * creating the string message directly.
407 *
408 * @param obj the object reference to check for nullity
409 * @param messageSupplier supplier of the detail message to be
410 * used in the event that a {@code NullPointerException} is thrown
411 * @param <T> the type of the reference
412 * @return {@code obj} if not {@code null}
413 * @throws NullPointerException if {@code obj} is {@code null}
414 * @since 1.8
415 */
416 public static <T> T requireNonNull(T obj, Supplier<String> messageSupplier) {
417 if (obj == null)
418 throw new NullPointerException(messageSupplier == null ?
419 null : messageSupplier.get());
420 return obj;
421 }
422
423 /**
424 * Checks if the {@code index} is within the bounds of the range from
425 * {@code 0} (inclusive) to {@code length} (exclusive).
426 *
427 * <p>The {@code index} is defined to be out of bounds if any of the
428 * following inequalities is true:
429 * <ul>
430 * <li>{@code index < 0}</li>
431 * <li>{@code index >= length}</li>
432 * <li>{@code length < 0}, which is implied from the former inequalities</li>
433 * </ul>
434 *
435 * @param index the index
436 * @param length the upper-bound (exclusive) of the range
437 * @return {@code index} if it is within bounds of the range
438 * @throws IndexOutOfBoundsException if the {@code index} is out of bounds
439 * @since 9
440 */
441 @ForceInline
442 public static
443 int checkIndex(int index, int length) {
444 return Preconditions.checkIndex(index, length, null);
445 }
446
447 /**
448 * Checks if the sub-range from {@code fromIndex} (inclusive) to
449 * {@code toIndex} (exclusive) is within the bounds of range from {@code 0}
450 * (inclusive) to {@code length} (exclusive).
451 *
452 * <p>The sub-range is defined to be out of bounds if any of the following
453 * inequalities is true:
454 * <ul>
455 * <li>{@code fromIndex < 0}</li>
456 * <li>{@code fromIndex > toIndex}</li>
457 * <li>{@code toIndex > length}</li>
458 * <li>{@code length < 0}, which is implied from the former inequalities</li>
459 * </ul>
460 *
461 * @param fromIndex the lower-bound (inclusive) of the sub-range
462 * @param toIndex the upper-bound (exclusive) of the sub-range
463 * @param length the upper-bound (exclusive) the range
464 * @return {@code fromIndex} if the sub-range within bounds of the range
465 * @throws IndexOutOfBoundsException if the sub-range is out of bounds
466 * @since 9
467 */
468 public static
469 int checkFromToIndex(int fromIndex, int toIndex, int length) {
470 return Preconditions.checkFromToIndex(fromIndex, toIndex, length, null);
471 }
472
473 /**
474 * Checks if the sub-range from {@code fromIndex} (inclusive) to
475 * {@code fromIndex + size} (exclusive) is within the bounds of range from
476 * {@code 0} (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 size < 0}</li>
483 * <li>{@code fromIndex + size > length}, taking into account integer overflow</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-interval
488 * @param size the size of the sub-range
489 * @param length the upper-bound (exclusive) of 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 checkFromIndexSize(int fromIndex, int size, int length) {
496 return Preconditions.checkFromIndexSize(fromIndex, size, length, null);
497 }
498
499 /**
500 * Return the size of the object in the heap.
501 *
502 * @param o an object
503 * @return the objects's size
504 * @since Valhalla
505 */
506 public static long getObjectSize(Object o) {
507 return Unsafe.getUnsafe().getObjectSize(o);
508 }
509
510 /**
511 * Checks if the {@code index} is within the bounds of the range from
512 * {@code 0} (inclusive) to {@code length} (exclusive).
513 *
514 * <p>The {@code index} is defined to be out of bounds if any of the
515 * following inequalities is true:
516 * <ul>
517 * <li>{@code index < 0}</li>
518 * <li>{@code index >= length}</li>
519 * <li>{@code length < 0}, which is implied from the former inequalities</li>
520 * </ul>
521 *
522 * @param index the index
523 * @param length the upper-bound (exclusive) of the range
524 * @return {@code index} if it is within bounds of the range
525 * @throws IndexOutOfBoundsException if the {@code index} is out of bounds
526 * @since 16
527 */
528 @ForceInline
529 public static
530 long checkIndex(long index, long length) {
531 return Preconditions.checkIndex(index, length, null);
532 }
533
534 /**
535 * Checks if the sub-range from {@code fromIndex} (inclusive) to
536 * {@code toIndex} (exclusive) is within the bounds of range from {@code 0}
537 * (inclusive) to {@code length} (exclusive).
538 *
539 * <p>The sub-range is defined to be out of bounds if any of the following
540 * inequalities is true:
541 * <ul>
542 * <li>{@code fromIndex < 0}</li>
543 * <li>{@code fromIndex > toIndex}</li>
544 * <li>{@code toIndex > length}</li>
545 * <li>{@code length < 0}, which is implied from the former inequalities</li>
546 * </ul>
547 *
548 * @param fromIndex the lower-bound (inclusive) of the sub-range
549 * @param toIndex the upper-bound (exclusive) of the sub-range
550 * @param length the upper-bound (exclusive) the range
551 * @return {@code fromIndex} if the sub-range within bounds of the range
552 * @throws IndexOutOfBoundsException if the sub-range is out of bounds
553 * @since 16
554 */
555 public static
556 long checkFromToIndex(long fromIndex, long toIndex, long length) {
557 return Preconditions.checkFromToIndex(fromIndex, toIndex, length, null);
558 }
559
560 /**
561 * Checks if the sub-range from {@code fromIndex} (inclusive) to
562 * {@code fromIndex + size} (exclusive) is within the bounds of range from
563 * {@code 0} (inclusive) to {@code length} (exclusive).
564 *
565 * <p>The sub-range is defined to be out of bounds if any of the following
566 * inequalities is true:
567 * <ul>
568 * <li>{@code fromIndex < 0}</li>
569 * <li>{@code size < 0}</li>
570 * <li>{@code fromIndex + size > length}, taking into account integer overflow</li>
571 * <li>{@code length < 0}, which is implied from the former inequalities</li>
572 * </ul>
573 *
574 * @param fromIndex the lower-bound (inclusive) of the sub-interval
575 * @param size the size of the sub-range
576 * @param length the upper-bound (exclusive) of the range
577 * @return {@code fromIndex} if the sub-range within bounds of the range
578 * @throws IndexOutOfBoundsException if the sub-range is out of bounds
579 * @since 16
580 */
581 public static
582 long checkFromIndexSize(long fromIndex, long size, long length) {
583 return Preconditions.checkFromIndexSize(fromIndex, size, length, null);
584 }
585 }