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 }