1 /*
  2  * Copyright (c) 2009, 2025, 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 
 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      * {@return {@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      * @see Object#equals(Object)
 61      */
 62     public static boolean equals(Object a, Object b) {
 63         return (a == b) || (a != null && a.equals(b));
 64     }
 65 
 66    /**
 67     * {@return {@code true} if the arguments are deeply equal to each other
 68     * and {@code false} otherwise}
 69     *
 70     * Two {@code null} values are deeply equal.  If both arguments are
 71     * arrays, the algorithm in {@link Arrays#deepEquals(Object[],
 72     * Object[]) Arrays.deepEquals} is used to determine equality.
 73     * Otherwise, equality is determined by using the {@link
 74     * Object#equals equals} method of the first argument.
 75     *
 76     * @param a an object
 77     * @param b an object to be compared with {@code a} for deep equality
 78     * @see Arrays#deepEquals(Object[], Object[])
 79     * @see Objects#equals(Object, Object)
 80     */
 81     public static boolean deepEquals(Object a, Object b) {
 82         if (a == b)
 83             return true;
 84         else if (a == null || b == null)
 85             return false;
 86         else
 87             return Arrays.deepEquals0(a, b);
 88     }
 89 
 90     /**
 91      * {@return the hash code of a non-{@code null} argument and 0 for
 92      * a {@code null} argument}
 93      *
 94      * @param o an object
 95      * @see Object#hashCode
 96      */
 97     public static int hashCode(Object o) {
 98         return o != null ? o.hashCode() : 0;
 99     }
100 
101    /**
102     * {@return a hash code for a sequence of input values} The hash
103     * code is generated as if all the input values were placed into an
104     * array, and that array were hashed by calling {@link
105     * Arrays#hashCode(Object[])}.
106     *
107     * <p>This method is useful for implementing {@link
108     * Object#hashCode()} on objects containing multiple fields. For
109     * example, if an object that has three fields, {@code x}, {@code
110     * y}, and {@code z}, one could write:
111     *
112     * <blockquote><pre>
113     * &#064;Override public int hashCode() {
114     *     return Objects.hash(x, y, z);
115     * }
116     * </pre></blockquote>
117     *
118     * <b>Warning: When a single object reference is supplied, the returned
119     * value does not equal the hash code of that object reference.</b> This
120     * value can be computed by calling {@link #hashCode(Object)}.
121     *
122     * @param values the values to be hashed
123     * @see Arrays#hashCode(Object[])
124     * @see List#hashCode
125     */
126     public static int hash(Object... values) {
127         return Arrays.hashCode(values);
128     }
129 
130     /**
131      * {@return the result of calling {@code toString} for a
132      * non-{@code null} argument and {@code "null"} for a
133      * {@code null} argument}
134      *
135      * @param o an object
136      * @see Object#toString
137      * @see String#valueOf(Object)
138      */
139     public static String toString(Object o) {
140         return String.valueOf(o);
141     }
142 
143     /**
144      * {@return the result of calling {@code toString} on the first
145      * argument if the first argument is not {@code null} and the
146      * second argument otherwise}
147      *
148      * @param o an object
149      * @param nullDefault string to return if the first argument is
150      *        {@code null}
151      * @see Objects#toString(Object)
152      */
153     public static String toString(Object o, String nullDefault) {
154         return (o != null) ? o.toString() : nullDefault;
155     }
156 
157     /**
158      * {@return a string equivalent to the string returned by {@code
159      * Object.toString} if that method and {@code hashCode} are not
160      * overridden}
161      *
162      * @implNote
163      * This method constructs a string for an object without calling
164      * any overridable methods of the object.
165      *
166      * @implSpec
167      * The method returns a string equivalent to:<br>
168      * {@code o.getClass().getName() + "@" + Integer.toHexString(System.identityHashCode(o))}
169      *
170      * @param o an object
171      * @throws NullPointerException if the argument is null
172      * @see Object#toString
173      * @see System#identityHashCode(Object)
174      * @since 19
175      */
176     public static String toIdentityString(Object o) {
177         requireNonNull(o);
178         return o.getClass().getName() + "@" + Integer.toHexString(System.identityHashCode(o));
179     }
180 
181    /**
182     * {@return {@code true} if the object is a non-null reference
183     * to an {@linkplain Class#isIdentity() identity object}, otherwise {@code false}}
184     *
185     * @apiNote
186     * If the parameter is {@code null}, there is no object
187     * and hence no class to check for identity; the return is {@code false}.
188     * To test for a {@linkplain Class#isValue() value object} use:
189     * {@snippet type="java" :
190     *     if (obj != null && !Objects.hasIdentity(obj)) {
191     *         // obj is a non-null value object
192     *     }
193     * }
194     * @param obj an object or {@code null}
195     * @since Valhalla
196     */
197    @PreviewFeature(feature = PreviewFeature.Feature.VALUE_OBJECTS)
198 //    @IntrinsicCandidate
199     public static boolean hasIdentity(Object obj) {
200         return (obj == null) ? false : obj.getClass().isIdentity();
201     }
202 
203    /**
204     * {@return {@code true} if the object is a non-null reference
205     * to a {@linkplain Class#isValue() value object}, otherwise {@code false}}
206     *
207     * @param obj an object or {@code null}
208     * @since Valhalla
209     */
210    @PreviewFeature(feature = PreviewFeature.Feature.VALUE_OBJECTS)
211 //    @IntrinsicCandidate
212     public static boolean isValueObject(Object obj) {
213         return (obj == null) ? false : obj.getClass().isValue();
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 <T> the type of the reference
221      * @return {@code obj} if {@code obj} is an identity object
222      * @throws NullPointerException if {@code obj} is {@code null}
223      * @throws IdentityException if {@code obj} is not an identity object
224      * @since Valhalla
225      */
226     @PreviewFeature(feature = PreviewFeature.Feature.VALUE_OBJECTS)
227     @ForceInline
228     public static <T> T requireIdentity(T obj) {
229         Objects.requireNonNull(obj);
230         if (!hasIdentity(obj))
231             throw new IdentityException(obj.getClass());
232         return obj;
233     }
234 
235     /**
236      * Checks that the specified object reference is an identity object.
237      *
238      * @param obj the object reference to check for identity
239      * @param message detail message to be used in the event that an
240      *        {@code IdentityException} is thrown; may be null
241      * @param <T> the type of the reference
242      * @return {@code obj} if {@code obj} is an identity object
243      * @throws NullPointerException if {@code obj} is {@code null}
244      * @throws IdentityException if {@code obj} is not an identity object
245      * @since Valhalla
246      */
247     @PreviewFeature(feature = PreviewFeature.Feature.VALUE_OBJECTS)
248     @ForceInline
249     public static <T> T requireIdentity(T obj, String message) {
250         Objects.requireNonNull(obj);
251         if (!hasIdentity(obj))
252             throw new IdentityException(message);
253         return obj;
254     }
255 
256     /**
257      * Checks that the specified object reference is an identity object.
258      *
259      * @param obj the object reference to check for identity
260      * @param messageSupplier supplier of the detail message to be
261      *        used in the event that an {@code IdentityException} is thrown; may be null
262      * @param <T> the type of the reference
263      * @return {@code obj} if {@code obj} is an identity object
264      * @throws NullPointerException if {@code obj} is {@code null}
265      * @throws IdentityException if {@code obj} is not an identity object
266      * @since Valhalla
267      */
268     @PreviewFeature(feature = PreviewFeature.Feature.VALUE_OBJECTS)
269     @ForceInline
270     public static <T> T requireIdentity(T obj, Supplier<String> messageSupplier) {
271         Objects.requireNonNull(obj);
272         if (!hasIdentity(obj))
273             throw new IdentityException(messageSupplier == null ?
274                     null : messageSupplier.get());
275         return obj;
276     }
277 
278     /**
279      * {@return 0 if the arguments are identical and {@code
280      * c.compare(a, b)} otherwise}
281      * Consequently, if both arguments are {@code null} 0
282      * is returned.
283      *
284      * <p>Note that if one of the arguments is {@code null}, a {@code
285      * NullPointerException} may or may not be thrown depending on
286      * what ordering policy, if any, the {@link Comparator Comparator}
287      * chooses to have for {@code null} values.
288      *
289      * @param <T> the type of the objects being compared
290      * @param a an object
291      * @param b an object to be compared with {@code a}
292      * @param c the {@code Comparator} to compare the first two arguments
293      * @see Comparable
294      * @see Comparator
295      */
296     public static <T> int compare(T a, T b, Comparator<? super T> c) {
297         return (a == b) ? 0 :  c.compare(a, b);
298     }
299 
300     /**
301      * Checks that the specified object reference is not {@code null}. This
302      * method is designed primarily for doing parameter validation in methods
303      * and constructors, as demonstrated below:
304      * <blockquote><pre>
305      * public Foo(Bar bar) {
306      *     this.bar = Objects.requireNonNull(bar);
307      * }
308      * </pre></blockquote>
309      *
310      * @param obj the object reference to check for nullity
311      * @param <T> the type of the reference
312      * @return {@code obj} if not {@code null}
313      * @throws NullPointerException if {@code obj} is {@code null}
314      */
315     @ForceInline
316     public static <T> T requireNonNull(T obj) {
317         if (obj == null)
318             throw new NullPointerException();
319         return obj;
320     }
321 
322     /**
323      * Checks that the specified object reference is not {@code null} and
324      * throws a customized {@link NullPointerException} if it is. This method
325      * is designed primarily for doing parameter validation in methods and
326      * constructors with multiple parameters, as demonstrated below:
327      * <blockquote><pre>
328      * public Foo(Bar bar, Baz baz) {
329      *     this.bar = Objects.requireNonNull(bar, "bar must not be null");
330      *     this.baz = Objects.requireNonNull(baz, "baz must not be null");
331      * }
332      * </pre></blockquote>
333      *
334      * @param obj     the object reference to check for nullity
335      * @param message detail message to be used in the event that a {@code
336      *                NullPointerException} is thrown
337      * @param <T> the type of the reference
338      * @return {@code obj} if not {@code null}
339      * @throws NullPointerException if {@code obj} is {@code null}
340      */
341     @ForceInline
342     public static <T> T requireNonNull(T obj, String message) {
343         if (obj == null)
344             throw new NullPointerException(message);
345         return obj;
346     }
347 
348     /**
349      * {@return {@code true} if the provided reference is {@code
350      * null}; {@code false} otherwise}
351      *
352      * @apiNote This method exists to be used as a
353      * {@link java.util.function.Predicate}, {@code filter(Objects::isNull)}
354      *
355      * @param obj a reference to be checked against {@code null}
356      *
357      * @see java.util.function.Predicate
358      * @since 1.8
359      */
360     public static boolean isNull(Object obj) {
361         return obj == null;
362     }
363 
364     /**
365      * {@return {@code true} if the provided reference is non-{@code null};
366      * {@code false} otherwise}
367      *
368      * @apiNote This method exists to be used as a
369      * {@link java.util.function.Predicate}, {@code filter(Objects::nonNull)}
370      *
371      * @param obj a reference to be checked against {@code null}
372      *
373      * @see java.util.function.Predicate
374      * @since 1.8
375      */
376     public static boolean nonNull(Object obj) {
377         return obj != null;
378     }
379 
380     /**
381      * {@return the first argument if it is non-{@code null} and
382      * otherwise the second argument if it is non-{@code null}}
383      *
384      * @param obj an object
385      * @param defaultObj a non-{@code null} object to return if the first argument
386      *                   is {@code null}
387      * @param <T> the type of the reference
388      * @throws NullPointerException if both {@code obj} is null and
389      *        {@code defaultObj} is {@code null}
390      * @since 9
391      */
392     public static <T> T requireNonNullElse(T obj, T defaultObj) {
393         return (obj != null) ? obj : requireNonNull(defaultObj, "defaultObj");
394     }
395 
396     /**
397      * {@return the first argument if it is non-{@code null} and
398      * otherwise the value from {@code supplier.get()} if it is
399      * non-{@code null}}
400      *
401      * @param obj an object
402      * @param supplier of a non-{@code null} object to return if the first argument
403      *                 is {@code null}
404      * @param <T> the type of the first argument and return type
405      * @throws NullPointerException if both {@code obj} is null and
406      *        either the {@code supplier} is {@code null} or
407      *        the {@code supplier.get()} value is {@code null}
408      * @since 9
409      */
410     public static <T> T requireNonNullElseGet(T obj, Supplier<? extends T> supplier) {
411         return (obj != null) ? obj
412                 : requireNonNull(requireNonNull(supplier, "supplier").get(), "supplier.get()");
413     }
414 
415     /**
416      * Checks that the specified object reference is not {@code null} and
417      * throws a customized {@link NullPointerException} if it is.
418      *
419      * <p>Unlike the method {@link #requireNonNull(Object, String)},
420      * this method allows creation of the message to be deferred until
421      * after the null check is made. While this may confer a
422      * performance advantage in the non-null case, when deciding to
423      * call this method care should be taken that the costs of
424      * creating the message supplier are less than the cost of just
425      * creating the string message directly.
426      *
427      * @param obj     the object reference to check for nullity
428      * @param messageSupplier supplier of the detail message to be
429      * used in the event that a {@code NullPointerException} is thrown
430      * @param <T> the type of the reference
431      * @return {@code obj} if not {@code null}
432      * @throws NullPointerException if {@code obj} is {@code null}
433      * @since 1.8
434      */
435     public static <T> T requireNonNull(T obj, Supplier<String> messageSupplier) {
436         if (obj == null)
437             throw new NullPointerException(messageSupplier == null ?
438                                            null : messageSupplier.get());
439         return obj;
440     }
441 
442     /**
443      * Checks if the {@code index} is within the bounds of the range from
444      * {@code 0} (inclusive) to {@code length} (exclusive).
445      *
446      * <p>The {@code index} is defined to be out of bounds if any of the
447      * following inequalities is true:
448      * <ul>
449      *  <li>{@code index < 0}</li>
450      *  <li>{@code index >= length}</li>
451      *  <li>{@code length < 0}, which is implied from the former inequalities</li>
452      * </ul>
453      *
454      * @param index the index
455      * @param length the upper-bound (exclusive) of the range
456      * @return {@code index} if it is within bounds of the range
457      * @throws IndexOutOfBoundsException if the {@code index} is out of bounds
458      * @since 9
459      */
460     @ForceInline
461     public static
462     int checkIndex(int index, int length) {
463         return Preconditions.checkIndex(index, length, null);
464     }
465 
466     /**
467      * Checks if the sub-range from {@code fromIndex} (inclusive) to
468      * {@code toIndex} (exclusive) is within the bounds of range from {@code 0}
469      * (inclusive) to {@code length} (exclusive).
470      *
471      * <p>The sub-range is defined to be out of bounds if any of the following
472      * inequalities is true:
473      * <ul>
474      *  <li>{@code fromIndex < 0}</li>
475      *  <li>{@code fromIndex > toIndex}</li>
476      *  <li>{@code toIndex > length}</li>
477      *  <li>{@code length < 0}, which is implied from the former inequalities</li>
478      * </ul>
479      *
480      * @param fromIndex the lower-bound (inclusive) of the sub-range
481      * @param toIndex the upper-bound (exclusive) of the sub-range
482      * @param length the upper-bound (exclusive) the range
483      * @return {@code fromIndex} if the sub-range within bounds of the range
484      * @throws IndexOutOfBoundsException if the sub-range is out of bounds
485      * @since 9
486      */
487     public static
488     int checkFromToIndex(int fromIndex, int toIndex, int length) {
489         return Preconditions.checkFromToIndex(fromIndex, toIndex, length, null);
490     }
491 
492     /**
493      * Checks if the sub-range from {@code fromIndex} (inclusive) to
494      * {@code fromIndex + size} (exclusive) is within the bounds of range from
495      * {@code 0} (inclusive) to {@code length} (exclusive).
496      *
497      * <p>The sub-range is defined to be out of bounds if any of the following
498      * inequalities is true:
499      * <ul>
500      *  <li>{@code fromIndex < 0}</li>
501      *  <li>{@code size < 0}</li>
502      *  <li>{@code fromIndex + size > length}, taking into account integer overflow</li>
503      *  <li>{@code length < 0}, which is implied from the former inequalities</li>
504      * </ul>
505      *
506      * @param fromIndex the lower-bound (inclusive) of the sub-interval
507      * @param size the size of the sub-range
508      * @param length the upper-bound (exclusive) of the range
509      * @return {@code fromIndex} if the sub-range within bounds of the range
510      * @throws IndexOutOfBoundsException if the sub-range is out of bounds
511      * @since 9
512      */
513     public static
514     int checkFromIndexSize(int fromIndex, int size, int length) {
515         return Preconditions.checkFromIndexSize(fromIndex, size, length, null);
516     }
517 
518     /**
519      * Checks if the {@code index} is within the bounds of the range from
520      * {@code 0} (inclusive) to {@code length} (exclusive).
521      *
522      * <p>The {@code index} is defined to be out of bounds if any of the
523      * following inequalities is true:
524      * <ul>
525      *  <li>{@code index < 0}</li>
526      *  <li>{@code index >= length}</li>
527      *  <li>{@code length < 0}, which is implied from the former inequalities</li>
528      * </ul>
529      *
530      * @param index the index
531      * @param length the upper-bound (exclusive) of the range
532      * @return {@code index} if it is within bounds of the range
533      * @throws IndexOutOfBoundsException if the {@code index} is out of bounds
534      * @since 16
535      */
536     @ForceInline
537     public static
538     long checkIndex(long index, long length) {
539         return Preconditions.checkIndex(index, length, null);
540     }
541 
542     /**
543      * Checks if the sub-range from {@code fromIndex} (inclusive) to
544      * {@code toIndex} (exclusive) is within the bounds of range from {@code 0}
545      * (inclusive) to {@code length} (exclusive).
546      *
547      * <p>The sub-range is defined to be out of bounds if any of the following
548      * inequalities is true:
549      * <ul>
550      *  <li>{@code fromIndex < 0}</li>
551      *  <li>{@code fromIndex > toIndex}</li>
552      *  <li>{@code toIndex > length}</li>
553      *  <li>{@code length < 0}, which is implied from the former inequalities</li>
554      * </ul>
555      *
556      * @param fromIndex the lower-bound (inclusive) of the sub-range
557      * @param toIndex the upper-bound (exclusive) of the sub-range
558      * @param length the upper-bound (exclusive) the range
559      * @return {@code fromIndex} if the sub-range within bounds of the range
560      * @throws IndexOutOfBoundsException if the sub-range is out of bounds
561      * @since 16
562      */
563     public static
564     long checkFromToIndex(long fromIndex, long toIndex, long length) {
565         return Preconditions.checkFromToIndex(fromIndex, toIndex, length, null);
566     }
567 
568     /**
569      * Checks if the sub-range from {@code fromIndex} (inclusive) to
570      * {@code fromIndex + size} (exclusive) is within the bounds of range from
571      * {@code 0} (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 size < 0}</li>
578      *  <li>{@code fromIndex + size > length}, taking into account integer overflow</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-interval
583      * @param size the size of the sub-range
584      * @param length the upper-bound (exclusive) of 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 checkFromIndexSize(long fromIndex, long size, long length) {
591         return Preconditions.checkFromIndexSize(fromIndex, size, length, null);
592     }
593 }