1 /*
2 * Copyright (c) 2009, 2020, 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.util.Preconditions;
29 import jdk.internal.vm.annotation.ForceInline;
30 import jdk.internal.misc.Unsafe;
31
32 import java.util.function.Supplier;
33
34 /**
35 * This class consists of {@code static} utility methods for operating
36 * on objects, or checking certain conditions before operation. These utilities
37 * include {@code null}-safe or {@code null}-tolerant methods for computing the
38 * hash code of an object, returning a string for an object, comparing two
39 * objects, and checking if indexes or sub-range values are out of bounds.
40 *
41 * @since 1.7
42 */
43 public final class Objects {
44 private Objects() {
45 throw new AssertionError("No java.util.Objects instances for you!");
46 }
47
48 /**
49 * Returns {@code true} if the arguments are equal to each other
50 * and {@code false} otherwise.
51 * Consequently, if both arguments are {@code null}, {@code true}
52 * is returned. Otherwise, if the first argument is not {@code
53 * null}, equality is determined by calling the {@link
54 * Object#equals equals} method of the first argument with the
55 * second argument of this method. Otherwise, {@code false} is
56 * returned.
57 *
58 * @param a an object
59 * @param b an object to be compared with {@code a} for equality
60 * @return {@code true} if the arguments are equal to each other
61 * and {@code false} otherwise
62 * @see Object#equals(Object)
63 */
64 public static boolean equals(Object a, Object b) {
65 return (a == b) || (a != null && a.equals(b));
66 }
67
68 /**
69 * Returns {@code true} if the arguments are deeply equal to each other
70 * and {@code false} otherwise.
71 *
72 * Two {@code null} values are deeply equal. If both arguments are
73 * arrays, the algorithm in {@link Arrays#deepEquals(Object[],
74 * Object[]) Arrays.deepEquals} is used to determine equality.
75 * Otherwise, equality is determined by using the {@link
76 * Object#equals equals} method of the first argument.
77 *
78 * @param a an object
79 * @param b an object to be compared with {@code a} for deep equality
80 * @return {@code true} if the arguments are deeply equal to each other
81 * and {@code false} otherwise
82 * @see Arrays#deepEquals(Object[], Object[])
83 * @see Objects#equals(Object, Object)
84 */
85 public static boolean deepEquals(Object a, Object b) {
86 if (a == b)
87 return true;
88 else if (a == null || b == null)
89 return false;
90 else
91 return Arrays.deepEquals0(a, b);
92 }
93
94 /**
95 * Returns the hash code of a non-{@code null} argument and 0 for
96 * a {@code null} argument.
97 *
98 * @param o an object
99 * @return the hash code of a non-{@code null} argument and 0 for
100 * a {@code null} argument
101 * @see Object#hashCode
102 */
103 public static int hashCode(Object o) {
104 return o != null ? o.hashCode() : 0;
105 }
106
107 /**
108 * Generates a hash code for a sequence of input values. The hash
109 * code is generated as if all the input values were placed into an
110 * array, and that array were hashed by calling {@link
111 * Arrays#hashCode(Object[])}.
112 *
113 * <p>This method is useful for implementing {@link
114 * Object#hashCode()} on objects containing multiple fields. For
115 * example, if an object that has three fields, {@code x}, {@code
116 * y}, and {@code z}, one could write:
117 *
118 * <blockquote><pre>
119 * @Override public int hashCode() {
120 * return Objects.hash(x, y, z);
121 * }
122 * </pre></blockquote>
123 *
124 * <b>Warning: When a single object reference is supplied, the returned
125 * value does not equal the hash code of that object reference.</b> This
126 * value can be computed by calling {@link #hashCode(Object)}.
127 *
128 * @param values the values to be hashed
129 * @return a hash value of the sequence of input values
130 * @see Arrays#hashCode(Object[])
131 * @see List#hashCode
132 */
133 public static int hash(Object... values) {
134 return Arrays.hashCode(values);
135 }
136
137 /**
138 * Returns the result of calling {@code toString} for a non-{@code
139 * null} argument and {@code "null"} for a {@code null} argument.
140 *
141 * @param o an object
142 * @return the result of calling {@code toString} for a non-{@code
143 * null} argument and {@code "null"} for a {@code null} argument
144 * @see Object#toString
145 * @see String#valueOf(Object)
146 */
147 public static String toString(Object o) {
148 return String.valueOf(o);
149 }
150
151 /**
152 * Returns the result of calling {@code toString} on the first
153 * argument if the first argument is not {@code null} and returns
154 * the second argument otherwise.
155 *
156 * @param o an object
157 * @param nullDefault string to return if the first argument is
158 * {@code null}
159 * @return the result of calling {@code toString} on the first
160 * argument if it is not {@code null} and the second argument
161 * otherwise.
162 * @see Objects#toString(Object)
163 */
164 public static String toString(Object o, String nullDefault) {
165 return (o != null) ? o.toString() : nullDefault;
166 }
167
168 /**
169 * Returns 0 if the arguments are identical and {@code
170 * c.compare(a, b)} otherwise.
171 * Consequently, if both arguments are {@code null} 0
172 * is returned.
173 *
174 * <p>Note that if one of the arguments is {@code null}, a {@code
175 * NullPointerException} may or may not be thrown depending on
176 * what ordering policy, if any, the {@link Comparator Comparator}
177 * chooses to have for {@code null} values.
178 *
179 * @param <T> the type of the objects being compared
180 * @param a an object
181 * @param b an object to be compared with {@code a}
182 * @param c the {@code Comparator} to compare the first two arguments
183 * @return 0 if the arguments are identical and {@code
184 * c.compare(a, b)} otherwise.
185 * @see Comparable
186 * @see Comparator
187 */
188 public static <T> int compare(T a, T b, Comparator<? super T> c) {
189 return (a == b) ? 0 : c.compare(a, b);
190 }
191
192 /**
193 * Checks that the specified object reference is not {@code null}. This
194 * method is designed primarily for doing parameter validation in methods
195 * and constructors, as demonstrated below:
196 * <blockquote><pre>
197 * public Foo(Bar bar) {
198 * this.bar = Objects.requireNonNull(bar);
199 * }
200 * </pre></blockquote>
201 *
202 * @param obj the object reference to check for nullity
203 * @param <T> the type of the reference
204 * @return {@code obj} if not {@code null}
205 * @throws NullPointerException if {@code obj} is {@code null}
206 */
207 public static <T> T requireNonNull(T obj) {
208 if (obj == null)
209 throw new NullPointerException();
210 return obj;
211 }
212
213 /**
214 * Checks that the specified object reference is not {@code null} and
215 * throws a customized {@link NullPointerException} if it is. This method
216 * is designed primarily for doing parameter validation in methods and
217 * constructors with multiple parameters, as demonstrated below:
218 * <blockquote><pre>
219 * public Foo(Bar bar, Baz baz) {
220 * this.bar = Objects.requireNonNull(bar, "bar must not be null");
221 * this.baz = Objects.requireNonNull(baz, "baz must not be null");
222 * }
223 * </pre></blockquote>
224 *
225 * @param obj the object reference to check for nullity
226 * @param message detail message to be used in the event that a {@code
227 * NullPointerException} is thrown
228 * @param <T> the type of the reference
229 * @return {@code obj} if not {@code null}
230 * @throws NullPointerException if {@code obj} is {@code null}
231 */
232 public static <T> T requireNonNull(T obj, String message) {
233 if (obj == null)
234 throw new NullPointerException(message);
235 return obj;
236 }
237
238 /**
239 * Returns {@code true} if the provided reference is {@code null} otherwise
240 * returns {@code false}.
241 *
242 * @apiNote This method exists to be used as a
243 * {@link java.util.function.Predicate}, {@code filter(Objects::isNull)}
244 *
245 * @param obj a reference to be checked against {@code null}
246 * @return {@code true} if the provided reference is {@code null} otherwise
247 * {@code false}
248 *
249 * @see java.util.function.Predicate
250 * @since 1.8
251 */
252 public static boolean isNull(Object obj) {
253 return obj == null;
254 }
255
256 /**
257 * Returns {@code true} if the provided reference is non-{@code null}
258 * otherwise returns {@code false}.
259 *
260 * @apiNote This method exists to be used as a
261 * {@link java.util.function.Predicate}, {@code filter(Objects::nonNull)}
262 *
263 * @param obj a reference to be checked against {@code null}
264 * @return {@code true} if the provided reference is non-{@code null}
265 * otherwise {@code false}
266 *
267 * @see java.util.function.Predicate
268 * @since 1.8
269 */
270 public static boolean nonNull(Object obj) {
271 return obj != null;
272 }
273
274 /**
275 * Returns the first argument if it is non-{@code null} and
276 * otherwise returns the non-{@code null} second argument.
277 *
278 * @param obj an object
279 * @param defaultObj a non-{@code null} object to return if the first argument
280 * is {@code null}
281 * @param <T> the type of the reference
282 * @return the first argument if it is non-{@code null} and
283 * otherwise the second argument if it is non-{@code null}
284 * @throws NullPointerException if both {@code obj} is null and
285 * {@code defaultObj} is {@code null}
286 * @since 9
287 */
288 public static <T> T requireNonNullElse(T obj, T defaultObj) {
289 return (obj != null) ? obj : requireNonNull(defaultObj, "defaultObj");
290 }
291
292 /**
293 * Returns the first argument if it is non-{@code null} and otherwise
294 * returns the non-{@code null} value of {@code supplier.get()}.
295 *
296 * @param obj an object
297 * @param supplier of a non-{@code null} object to return if the first argument
298 * is {@code null}
299 * @param <T> the type of the first argument and return type
300 * @return the first argument if it is non-{@code null} and otherwise
301 * the value from {@code supplier.get()} if it is non-{@code null}
302 * @throws NullPointerException if both {@code obj} is null and
303 * either the {@code supplier} is {@code null} or
304 * the {@code supplier.get()} value is {@code null}
305 * @since 9
306 */
307 public static <T> T requireNonNullElseGet(T obj, Supplier<? extends T> supplier) {
308 return (obj != null) ? obj
309 : requireNonNull(requireNonNull(supplier, "supplier").get(), "supplier.get()");
310 }
311
312 /**
313 * Checks that the specified object reference is not {@code null} and
314 * throws a customized {@link NullPointerException} if it is.
315 *
316 * <p>Unlike the method {@link #requireNonNull(Object, String)},
317 * this method allows creation of the message to be deferred until
318 * after the null check is made. While this may confer a
319 * performance advantage in the non-null case, when deciding to
320 * call this method care should be taken that the costs of
321 * creating the message supplier are less than the cost of just
322 * creating the string message directly.
323 *
324 * @param obj the object reference to check for nullity
325 * @param messageSupplier supplier of the detail message to be
326 * used in the event that a {@code NullPointerException} is thrown
327 * @param <T> the type of the reference
328 * @return {@code obj} if not {@code null}
329 * @throws NullPointerException if {@code obj} is {@code null}
330 * @since 1.8
331 */
332 public static <T> T requireNonNull(T obj, Supplier<String> messageSupplier) {
333 if (obj == null)
334 throw new NullPointerException(messageSupplier == null ?
335 null : messageSupplier.get());
336 return obj;
337 }
338
339 /**
340 * Checks if the {@code index} is within the bounds of the range from
341 * {@code 0} (inclusive) to {@code length} (exclusive).
342 *
343 * <p>The {@code index} is defined to be out of bounds if any of the
344 * following inequalities is true:
345 * <ul>
346 * <li>{@code index < 0}</li>
347 * <li>{@code index >= length}</li>
348 * <li>{@code length < 0}, which is implied from the former inequalities</li>
349 * </ul>
350 *
351 * @param index the index
352 * @param length the upper-bound (exclusive) of the range
353 * @return {@code index} if it is within bounds of the range
354 * @throws IndexOutOfBoundsException if the {@code index} is out of bounds
355 * @since 9
356 */
357 @ForceInline
358 public static
359 int checkIndex(int index, int length) {
360 return Preconditions.checkIndex(index, length, null);
361 }
362
363 /**
364 * Checks if the sub-range from {@code fromIndex} (inclusive) to
365 * {@code toIndex} (exclusive) is within the bounds of range from {@code 0}
366 * (inclusive) to {@code length} (exclusive).
367 *
368 * <p>The sub-range is defined to be out of bounds if any of the following
369 * inequalities is true:
370 * <ul>
371 * <li>{@code fromIndex < 0}</li>
372 * <li>{@code fromIndex > toIndex}</li>
373 * <li>{@code toIndex > length}</li>
374 * <li>{@code length < 0}, which is implied from the former inequalities</li>
375 * </ul>
376 *
377 * @param fromIndex the lower-bound (inclusive) of the sub-range
378 * @param toIndex the upper-bound (exclusive) of the sub-range
379 * @param length the upper-bound (exclusive) the range
380 * @return {@code fromIndex} if the sub-range within bounds of the range
381 * @throws IndexOutOfBoundsException if the sub-range is out of bounds
382 * @since 9
383 */
384 public static
385 int checkFromToIndex(int fromIndex, int toIndex, int length) {
386 return Preconditions.checkFromToIndex(fromIndex, toIndex, length, null);
387 }
388
389 /**
390 * Checks if the sub-range from {@code fromIndex} (inclusive) to
391 * {@code fromIndex + size} (exclusive) is within the bounds of range from
392 * {@code 0} (inclusive) to {@code length} (exclusive).
393 *
394 * <p>The sub-range is defined to be out of bounds if any of the following
395 * inequalities is true:
396 * <ul>
397 * <li>{@code fromIndex < 0}</li>
398 * <li>{@code size < 0}</li>
399 * <li>{@code fromIndex + size > length}, taking into account integer overflow</li>
400 * <li>{@code length < 0}, which is implied from the former inequalities</li>
401 * </ul>
402 *
403 * @param fromIndex the lower-bound (inclusive) of the sub-interval
404 * @param size the size of the sub-range
405 * @param length the upper-bound (exclusive) of the range
406 * @return {@code fromIndex} if the sub-range within bounds of the range
407 * @throws IndexOutOfBoundsException if the sub-range is out of bounds
408 * @since 9
409 */
410 public static
411 int checkFromIndexSize(int fromIndex, int size, int length) {
412 return Preconditions.checkFromIndexSize(fromIndex, size, length, null);
413 }
414
415 /**
416 * Return the size of the object in the heap.
417 *
418 * @param o an object
419 * @return the objects's size
420 * @since Valhalla
421 */
422 public static long getObjectSize(Object o) {
423 return Unsafe.getUnsafe().getObjectSize(o);
424 }
425
426 /**
427 * Checks if the {@code index} is within the bounds of the range from
428 * {@code 0} (inclusive) to {@code length} (exclusive).
429 *
430 * <p>The {@code index} is defined to be out of bounds if any of the
431 * following inequalities is true:
432 * <ul>
433 * <li>{@code index < 0}</li>
434 * <li>{@code index >= length}</li>
435 * <li>{@code length < 0}, which is implied from the former inequalities</li>
436 * </ul>
437 *
438 * @param index the index
439 * @param length the upper-bound (exclusive) of the range
440 * @return {@code index} if it is within bounds of the range
441 * @throws IndexOutOfBoundsException if the {@code index} is out of bounds
442 * @since 16
443 */
444 @ForceInline
445 public static
446 long checkIndex(long index, long length) {
447 return Preconditions.checkIndex(index, length, null);
448 }
449
450 /**
451 * Checks if the sub-range from {@code fromIndex} (inclusive) to
452 * {@code toIndex} (exclusive) is within the bounds of range from {@code 0}
453 * (inclusive) to {@code length} (exclusive).
454 *
455 * <p>The sub-range is defined to be out of bounds if any of the following
456 * inequalities is true:
457 * <ul>
458 * <li>{@code fromIndex < 0}</li>
459 * <li>{@code fromIndex > toIndex}</li>
460 * <li>{@code toIndex > length}</li>
461 * <li>{@code length < 0}, which is implied from the former inequalities</li>
462 * </ul>
463 *
464 * @param fromIndex the lower-bound (inclusive) of the sub-range
465 * @param toIndex the upper-bound (exclusive) of the sub-range
466 * @param length the upper-bound (exclusive) the range
467 * @return {@code fromIndex} if the sub-range within bounds of the range
468 * @throws IndexOutOfBoundsException if the sub-range is out of bounds
469 * @since 16
470 */
471 public static
472 long checkFromToIndex(long fromIndex, long toIndex, long length) {
473 return Preconditions.checkFromToIndex(fromIndex, toIndex, length, null);
474 }
475
476 /**
477 * Checks if the sub-range from {@code fromIndex} (inclusive) to
478 * {@code fromIndex + size} (exclusive) is within the bounds of range from
479 * {@code 0} (inclusive) to {@code length} (exclusive).
480 *
481 * <p>The sub-range is defined to be out of bounds if any of the following
482 * inequalities is true:
483 * <ul>
484 * <li>{@code fromIndex < 0}</li>
485 * <li>{@code size < 0}</li>
486 * <li>{@code fromIndex + size > length}, taking into account integer overflow</li>
487 * <li>{@code length < 0}, which is implied from the former inequalities</li>
488 * </ul>
489 *
490 * @param fromIndex the lower-bound (inclusive) of the sub-interval
491 * @param size the size of the sub-range
492 * @param length the upper-bound (exclusive) of the range
493 * @return {@code fromIndex} if the sub-range within bounds of the range
494 * @throws IndexOutOfBoundsException if the sub-range is out of bounds
495 * @since 16
496 */
497 public static
498 long checkFromIndexSize(long fromIndex, long size, long length) {
499 return Preconditions.checkFromIndexSize(fromIndex, size, length, null);
500 }
501 /**
502 * {@return a new instance of an unspecified class}
503 * The object has a unique identity; no other references to it exist.
504 * It can be used for synchronization, or where a placeholder Object is needed.
505 * Use this method to avoid relying on the {@linkplain Object#Object() Object constructor}.
506 *
507 * @since 17
508 */
509 public static Object newIdentity() {
510 return new Object() {};
511 }
512 }