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.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     * &#064;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      * {@return a string equivalent to the string returned by {@code
170      * Object.toString} if that method and {@code hashCode} are not
171      * overridden}
172      *
173      * @implNote
174      * This method constructs a string for an object without calling
175      * any overridable methods of the object.
176      *
177      * @implSpec
178      * The method returns a string equivalent to:<br>
179      * {@code o.getClass().getName() + "@" + Integer.toHexString(System.identityHashCode(o))}
180      *
181      * @param o an object
182      * @throws NullPointerException if the argument is null
183      * @see Object#toString
184      * @see System#identityHashCode(Object)
185      * @since 19
186      */
187     public static String toIdentityString(Object o) {
188         requireNonNull(o);
189         return o.getClass().getName() + "@" + Integer.toHexString(System.identityHashCode(o));
190     }
191 
192     /**
193      * Checks that the specified object reference is an identity object.
194      *
195      * @param obj the object reference to check for identity
196      * @param <T> the type of the reference
197      * @return {@code obj} if {@code obj} is an identity object
198      * @throws NullPointerException if {@code obj} is {@code null}
199      * @throws IdentityException if {@code obj} is not an identity object
200      * @since Valhalla
201      */
202     @ForceInline
203     public static <T> T requireIdentity(T obj) {
204         Objects.requireNonNull(obj);
205         var cl = obj.getClass();
206         if (cl.isValue())
207             throw new IdentityException(cl);
208         return obj;
209     }
210 
211     /**
212      * Checks that the specified object reference is an identity object.
213      *
214      * @param obj the object reference to check for identity
215      * @param message detail message to be used in the event that an
216      *        {@code IdentityException} is thrown; may be null
217      * @param <T> the type of the reference
218      * @return {@code obj} if {@code obj} is an identity object
219      * @throws NullPointerException if {@code obj} is {@code null}
220      * @throws IdentityException if {@code obj} is not an identity object
221      * @since Valhalla
222      */
223     @ForceInline
224     public static <T> T requireIdentity(T obj, String message) {
225         Objects.requireNonNull(obj);
226         if (obj.getClass().isValue())
227             throw new IdentityException(message);
228         return obj;
229     }
230 
231     /**
232      * Checks that the specified object reference is an identity object.
233      *
234      * @param obj the object reference to check for identity
235      * @param messageSupplier supplier of the detail message to be
236      *        used in the event that an {@code IdentityException} is thrown; may be null
237      * @param <T> the type of the reference
238      * @return {@code obj} if {@code obj} is an identity object
239      * @throws NullPointerException if {@code obj} is {@code null}
240      * @throws IdentityException if {@code obj} is not an identity object
241      * @since Valhalla
242      */
243     @ForceInline
244     public static <T> T requireIdentity(T obj, Supplier<String> messageSupplier) {
245         Objects.requireNonNull(obj);
246         if (obj.getClass().isValue())
247             throw new IdentityException(messageSupplier == null ?
248                     null : messageSupplier.get());
249         return obj;
250     }
251 
252     /**
253      * Returns 0 if the arguments are identical and {@code
254      * c.compare(a, b)} otherwise.
255      * Consequently, if both arguments are {@code null} 0
256      * is returned.
257      *
258      * <p>Note that if one of the arguments is {@code null}, a {@code
259      * NullPointerException} may or may not be thrown depending on
260      * what ordering policy, if any, the {@link Comparator Comparator}
261      * chooses to have for {@code null} values.
262      *
263      * @param <T> the type of the objects being compared
264      * @param a an object
265      * @param b an object to be compared with {@code a}
266      * @param c the {@code Comparator} to compare the first two arguments
267      * @return 0 if the arguments are identical and {@code
268      * c.compare(a, b)} otherwise.
269      * @see Comparable
270      * @see Comparator
271      */
272     public static <T> int compare(T a, T b, Comparator<? super T> c) {
273         return (a == b) ? 0 :  c.compare(a, b);
274     }
275 
276     /**
277      * Checks that the specified object reference is not {@code null}. This
278      * method is designed primarily for doing parameter validation in methods
279      * and constructors, as demonstrated below:
280      * <blockquote><pre>
281      * public Foo(Bar bar) {
282      *     this.bar = Objects.requireNonNull(bar);
283      * }
284      * </pre></blockquote>
285      *
286      * @param obj the object reference to check for nullity
287      * @param <T> the type of the reference
288      * @return {@code obj} if not {@code null}
289      * @throws NullPointerException if {@code obj} is {@code null}
290      */
291     @ForceInline
292     public static <T> T requireNonNull(T obj) {
293         if (obj == null)
294             throw new NullPointerException();
295         return obj;
296     }
297 
298     /**
299      * Checks that the specified object reference is not {@code null} and
300      * throws a customized {@link NullPointerException} if it is. This method
301      * is designed primarily for doing parameter validation in methods and
302      * constructors with multiple parameters, as demonstrated below:
303      * <blockquote><pre>
304      * public Foo(Bar bar, Baz baz) {
305      *     this.bar = Objects.requireNonNull(bar, "bar must not be null");
306      *     this.baz = Objects.requireNonNull(baz, "baz must not be null");
307      * }
308      * </pre></blockquote>
309      *
310      * @param obj     the object reference to check for nullity
311      * @param message detail message to be used in the event that a {@code
312      *                NullPointerException} is thrown
313      * @param <T> the type of the reference
314      * @return {@code obj} if not {@code null}
315      * @throws NullPointerException if {@code obj} is {@code null}
316      */
317     @ForceInline
318     public static <T> T requireNonNull(T obj, String message) {
319         if (obj == null)
320             throw new NullPointerException(message);
321         return obj;
322     }
323 
324     /**
325      * Returns {@code true} if the provided reference is {@code null} otherwise
326      * returns {@code false}.
327      *
328      * @apiNote This method exists to be used as a
329      * {@link java.util.function.Predicate}, {@code filter(Objects::isNull)}
330      *
331      * @param obj a reference to be checked against {@code null}
332      * @return {@code true} if the provided reference is {@code null} otherwise
333      * {@code false}
334      *
335      * @see java.util.function.Predicate
336      * @since 1.8
337      */
338     public static boolean isNull(Object obj) {
339         return obj == null;
340     }
341 
342     /**
343      * Returns {@code true} if the provided reference is non-{@code null}
344      * otherwise returns {@code false}.
345      *
346      * @apiNote This method exists to be used as a
347      * {@link java.util.function.Predicate}, {@code filter(Objects::nonNull)}
348      *
349      * @param obj a reference to be checked against {@code null}
350      * @return {@code true} if the provided reference is non-{@code null}
351      * otherwise {@code false}
352      *
353      * @see java.util.function.Predicate
354      * @since 1.8
355      */
356     public static boolean nonNull(Object obj) {
357         return obj != null;
358     }
359 
360     /**
361      * Returns the first argument if it is non-{@code null} and
362      * otherwise returns the non-{@code null} second argument.
363      *
364      * @param obj an object
365      * @param defaultObj a non-{@code null} object to return if the first argument
366      *                   is {@code null}
367      * @param <T> the type of the reference
368      * @return the first argument if it is non-{@code null} and
369      *        otherwise the second argument if it is non-{@code null}
370      * @throws NullPointerException if both {@code obj} is null and
371      *        {@code defaultObj} is {@code null}
372      * @since 9
373      */
374     public static <T> T requireNonNullElse(T obj, T defaultObj) {
375         return (obj != null) ? obj : requireNonNull(defaultObj, "defaultObj");
376     }
377 
378     /**
379      * Returns the first argument if it is non-{@code null} and otherwise
380      * returns the non-{@code null} value of {@code supplier.get()}.
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      * @return the first argument if it is non-{@code null} and otherwise
387      *         the value from {@code supplier.get()} if it is non-{@code null}
388      * @throws NullPointerException if both {@code obj} is null and
389      *        either the {@code supplier} is {@code null} or
390      *        the {@code supplier.get()} value is {@code null}
391      * @since 9
392      */
393     public static <T> T requireNonNullElseGet(T obj, Supplier<? extends T> supplier) {
394         return (obj != null) ? obj
395                 : requireNonNull(requireNonNull(supplier, "supplier").get(), "supplier.get()");
396     }
397 
398     /**
399      * Checks that the specified object reference is not {@code null} and
400      * throws a customized {@link NullPointerException} if it is.
401      *
402      * <p>Unlike the method {@link #requireNonNull(Object, String)},
403      * this method allows creation of the message to be deferred until
404      * after the null check is made. While this may confer a
405      * performance advantage in the non-null case, when deciding to
406      * call this method care should be taken that the costs of
407      * creating the message supplier are less than the cost of just
408      * creating the string message directly.
409      *
410      * @param obj     the object reference to check for nullity
411      * @param messageSupplier supplier of the detail message to be
412      * used in the event that a {@code NullPointerException} is thrown
413      * @param <T> the type of the reference
414      * @return {@code obj} if not {@code null}
415      * @throws NullPointerException if {@code obj} is {@code null}
416      * @since 1.8
417      */
418     public static <T> T requireNonNull(T obj, Supplier<String> messageSupplier) {
419         if (obj == null)
420             throw new NullPointerException(messageSupplier == null ?
421                                            null : messageSupplier.get());
422         return obj;
423     }
424 
425     /**
426      * Checks if the {@code index} is within the bounds of the range from
427      * {@code 0} (inclusive) to {@code length} (exclusive).
428      *
429      * <p>The {@code index} is defined to be out of bounds if any of the
430      * following inequalities is true:
431      * <ul>
432      *  <li>{@code index < 0}</li>
433      *  <li>{@code index >= length}</li>
434      *  <li>{@code length < 0}, which is implied from the former inequalities</li>
435      * </ul>
436      *
437      * @param index the index
438      * @param length the upper-bound (exclusive) of the range
439      * @return {@code index} if it is within bounds of the range
440      * @throws IndexOutOfBoundsException if the {@code index} is out of bounds
441      * @since 9
442      */
443     @ForceInline
444     public static
445     int checkIndex(int index, int length) {
446         return Preconditions.checkIndex(index, length, null);
447     }
448 
449     /**
450      * Checks if the sub-range from {@code fromIndex} (inclusive) to
451      * {@code toIndex} (exclusive) is within the bounds of range from {@code 0}
452      * (inclusive) to {@code length} (exclusive).
453      *
454      * <p>The sub-range is defined to be out of bounds if any of the following
455      * inequalities is true:
456      * <ul>
457      *  <li>{@code fromIndex < 0}</li>
458      *  <li>{@code fromIndex > toIndex}</li>
459      *  <li>{@code toIndex > length}</li>
460      *  <li>{@code length < 0}, which is implied from the former inequalities</li>
461      * </ul>
462      *
463      * @param fromIndex the lower-bound (inclusive) of the sub-range
464      * @param toIndex the upper-bound (exclusive) of the sub-range
465      * @param length the upper-bound (exclusive) the range
466      * @return {@code fromIndex} if the sub-range within bounds of the range
467      * @throws IndexOutOfBoundsException if the sub-range is out of bounds
468      * @since 9
469      */
470     public static
471     int checkFromToIndex(int fromIndex, int toIndex, int length) {
472         return Preconditions.checkFromToIndex(fromIndex, toIndex, length, null);
473     }
474 
475     /**
476      * Checks if the sub-range from {@code fromIndex} (inclusive) to
477      * {@code fromIndex + size} (exclusive) is within the bounds of range from
478      * {@code 0} (inclusive) to {@code length} (exclusive).
479      *
480      * <p>The sub-range is defined to be out of bounds if any of the following
481      * inequalities is true:
482      * <ul>
483      *  <li>{@code fromIndex < 0}</li>
484      *  <li>{@code size < 0}</li>
485      *  <li>{@code fromIndex + size > length}, taking into account integer overflow</li>
486      *  <li>{@code length < 0}, which is implied from the former inequalities</li>
487      * </ul>
488      *
489      * @param fromIndex the lower-bound (inclusive) of the sub-interval
490      * @param size the size of the sub-range
491      * @param length the upper-bound (exclusive) of the range
492      * @return {@code fromIndex} if the sub-range within bounds of the range
493      * @throws IndexOutOfBoundsException if the sub-range is out of bounds
494      * @since 9
495      */
496     public static
497     int checkFromIndexSize(int fromIndex, int size, int length) {
498         return Preconditions.checkFromIndexSize(fromIndex, size, length, null);
499     }
500 
501     /**
502      * Return the size of the object in the heap.
503      *
504      * @param o an object
505      * @return the objects's size
506      * @since Valhalla
507      */
508     public static long getObjectSize(Object o) {
509         return Unsafe.getUnsafe().getObjectSize(o);
510     }
511 
512     /**
513      * Checks if the {@code index} is within the bounds of the range from
514      * {@code 0} (inclusive) to {@code length} (exclusive).
515      *
516      * <p>The {@code index} is defined to be out of bounds if any of the
517      * following inequalities is true:
518      * <ul>
519      *  <li>{@code index < 0}</li>
520      *  <li>{@code index >= length}</li>
521      *  <li>{@code length < 0}, which is implied from the former inequalities</li>
522      * </ul>
523      *
524      * @param index the index
525      * @param length the upper-bound (exclusive) of the range
526      * @return {@code index} if it is within bounds of the range
527      * @throws IndexOutOfBoundsException if the {@code index} is out of bounds
528      * @since 16
529      */
530     @ForceInline
531     public static
532     long checkIndex(long index, long length) {
533         return Preconditions.checkIndex(index, length, null);
534     }
535 
536     /**
537      * Checks if the sub-range from {@code fromIndex} (inclusive) to
538      * {@code toIndex} (exclusive) is within the bounds of range from {@code 0}
539      * (inclusive) to {@code length} (exclusive).
540      *
541      * <p>The sub-range is defined to be out of bounds if any of the following
542      * inequalities is true:
543      * <ul>
544      *  <li>{@code fromIndex < 0}</li>
545      *  <li>{@code fromIndex > toIndex}</li>
546      *  <li>{@code toIndex > length}</li>
547      *  <li>{@code length < 0}, which is implied from the former inequalities</li>
548      * </ul>
549      *
550      * @param fromIndex the lower-bound (inclusive) of the sub-range
551      * @param toIndex the upper-bound (exclusive) of the sub-range
552      * @param length the upper-bound (exclusive) the range
553      * @return {@code fromIndex} if the sub-range within bounds of the range
554      * @throws IndexOutOfBoundsException if the sub-range is out of bounds
555      * @since 16
556      */
557     public static
558     long checkFromToIndex(long fromIndex, long toIndex, long length) {
559         return Preconditions.checkFromToIndex(fromIndex, toIndex, length, null);
560     }
561 
562     /**
563      * Checks if the sub-range from {@code fromIndex} (inclusive) to
564      * {@code fromIndex + size} (exclusive) is within the bounds of range from
565      * {@code 0} (inclusive) to {@code length} (exclusive).
566      *
567      * <p>The sub-range is defined to be out of bounds if any of the following
568      * inequalities is true:
569      * <ul>
570      *  <li>{@code fromIndex < 0}</li>
571      *  <li>{@code size < 0}</li>
572      *  <li>{@code fromIndex + size > length}, taking into account integer overflow</li>
573      *  <li>{@code length < 0}, which is implied from the former inequalities</li>
574      * </ul>
575      *
576      * @param fromIndex the lower-bound (inclusive) of the sub-interval
577      * @param size the size of the sub-range
578      * @param length the upper-bound (exclusive) of the range
579      * @return {@code fromIndex} if the sub-range within bounds of the range
580      * @throws IndexOutOfBoundsException if the sub-range is out of bounds
581      * @since 16
582      */
583     public static
584     long checkFromIndexSize(long fromIndex, long size, long length) {
585         return Preconditions.checkFromIndexSize(fromIndex, size, length, null);
586     }
587 }
--- EOF ---