rev 14354 : 8155794: Move Objects.checkIndex BiFunction accepting methods to an internal package
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   1 /*
   2  * Copyright (c) 2009, 2016, 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
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   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 


  31 import java.util.function.Supplier;
  32 
  33 /**
  34  * This class consists of {@code static} utility methods for operating
  35  * on objects, or checking certain conditions before operation.  These utilities
  36  * include {@code null}-safe or {@code null}-tolerant methods for computing the
  37  * hash code of an object, returning a string for an object, comparing two
  38  * objects, and checking if indexes or sub-range values are out-of-bounds.
  39  *
  40  * @apiNote
  41  * Static methods such as {@link Objects#checkIndex},
  42  * {@link Objects#checkFromToIndex}, and {@link Objects#checkFromIndexSize} are
  43  * provided for the convenience of checking if values corresponding to indexes
  44  * and sub-ranges are out-of-bounds.
  45  * Variations of these static methods support customization of the runtime
  46  * exception, and corresponding exception detail message, that is thrown when
  47  * values are out-of-bounds.  Such methods accept a functional interface
  48  * argument, instances of {@code BiFunction}, that maps out-of-bound values to a
  49  * runtime exception.  Care should be taken when using such methods in
  50  * combination with an argument that is a lambda expression, method reference or
  51  * class that capture values.  In such cases the cost of capture, related to
  52  * functional interface allocation, may exceed the cost of checking bounds.
  53  *
  54  * @since 1.7
  55  */
  56 public final class Objects {
  57     private Objects() {
  58         throw new AssertionError("No java.util.Objects instances for you!");
  59     }
  60 
  61     /**
  62      * Returns {@code true} if the arguments are equal to each other
  63      * and {@code false} otherwise.
  64      * Consequently, if both arguments are {@code null}, {@code true}
  65      * is returned and if exactly one argument is {@code null}, {@code
  66      * false} is returned.  Otherwise, equality is determined by using
  67      * the {@link Object#equals equals} method of the first
  68      * argument.
  69      *
  70      * @param a an object
  71      * @param b an object to be compared with {@code a} for equality
  72      * @return {@code true} if the arguments are equal to each other
  73      * and {@code false} otherwise
  74      * @see Object#equals(Object)
  75      */
  76     public static boolean equals(Object a, Object b) {
  77         return (a == b) || (a != null && a.equals(b));
  78     }
  79 
  80    /**
  81     * Returns {@code true} if the arguments are deeply equal to each other
  82     * and {@code false} otherwise.
  83     *
  84     * Two {@code null} values are deeply equal.  If both arguments are
  85     * arrays, the algorithm in {@link Arrays#deepEquals(Object[],
  86     * Object[]) Arrays.deepEquals} is used to determine equality.
  87     * Otherwise, equality is determined by using the {@link
  88     * Object#equals equals} method of the first argument.
  89     *
  90     * @param a an object
  91     * @param b an object to be compared with {@code a} for deep equality
  92     * @return {@code true} if the arguments are deeply equal to each other
  93     * and {@code false} otherwise
  94     * @see Arrays#deepEquals(Object[], Object[])
  95     * @see Objects#equals(Object, Object)
  96     */
  97     public static boolean deepEquals(Object a, Object b) {
  98         if (a == b)
  99             return true;
 100         else if (a == null || b == null)
 101             return false;
 102         else
 103             return Arrays.deepEquals0(a, b);
 104     }
 105 
 106     /**
 107      * Returns the hash code of a non-{@code null} argument and 0 for
 108      * a {@code null} argument.
 109      *
 110      * @param o an object
 111      * @return the hash code of a non-{@code null} argument and 0 for
 112      * a {@code null} argument
 113      * @see Object#hashCode
 114      */
 115     public static int hashCode(Object o) {
 116         return o != null ? o.hashCode() : 0;
 117     }
 118 
 119    /**
 120     * Generates a hash code for a sequence of input values. The hash
 121     * code is generated as if all the input values were placed into an
 122     * array, and that array were hashed by calling {@link
 123     * Arrays#hashCode(Object[])}.
 124     *
 125     * <p>This method is useful for implementing {@link
 126     * Object#hashCode()} on objects containing multiple fields. For
 127     * example, if an object that has three fields, {@code x}, {@code
 128     * y}, and {@code z}, one could write:
 129     *
 130     * <blockquote><pre>
 131     * @Override public int hashCode() {
 132     *     return Objects.hash(x, y, z);
 133     * }
 134     * </pre></blockquote>
 135     *
 136     * <b>Warning: When a single object reference is supplied, the returned
 137     * value does not equal the hash code of that object reference.</b> This
 138     * value can be computed by calling {@link #hashCode(Object)}.
 139     *
 140     * @param values the values to be hashed
 141     * @return a hash value of the sequence of input values
 142     * @see Arrays#hashCode(Object[])
 143     * @see List#hashCode
 144     */
 145     public static int hash(Object... values) {
 146         return Arrays.hashCode(values);
 147     }
 148 
 149     /**
 150      * Returns the result of calling {@code toString} for a non-{@code
 151      * null} argument and {@code "null"} for a {@code null} argument.
 152      *
 153      * @param o an object
 154      * @return the result of calling {@code toString} for a non-{@code
 155      * null} argument and {@code "null"} for a {@code null} argument
 156      * @see Object#toString
 157      * @see String#valueOf(Object)
 158      */
 159     public static String toString(Object o) {
 160         return String.valueOf(o);
 161     }
 162 
 163     /**
 164      * Returns the result of calling {@code toString} on the first
 165      * argument if the first argument is not {@code null} and returns
 166      * the second argument otherwise.
 167      *
 168      * @param o an object
 169      * @param nullDefault string to return if the first argument is
 170      *        {@code null}
 171      * @return the result of calling {@code toString} on the first
 172      * argument if it is not {@code null} and the second argument
 173      * otherwise.
 174      * @see Objects#toString(Object)
 175      */
 176     public static String toString(Object o, String nullDefault) {
 177         return (o != null) ? o.toString() : nullDefault;
 178     }
 179 
 180     /**
 181      * Returns 0 if the arguments are identical and {@code
 182      * c.compare(a, b)} otherwise.
 183      * Consequently, if both arguments are {@code null} 0
 184      * is returned.
 185      *
 186      * <p>Note that if one of the arguments is {@code null}, a {@code
 187      * NullPointerException} may or may not be thrown depending on
 188      * what ordering policy, if any, the {@link Comparator Comparator}
 189      * chooses to have for {@code null} values.
 190      *
 191      * @param <T> the type of the objects being compared
 192      * @param a an object
 193      * @param b an object to be compared with {@code a}
 194      * @param c the {@code Comparator} to compare the first two arguments
 195      * @return 0 if the arguments are identical and {@code
 196      * c.compare(a, b)} otherwise.
 197      * @see Comparable
 198      * @see Comparator
 199      */
 200     public static <T> int compare(T a, T b, Comparator<? super T> c) {
 201         return (a == b) ? 0 :  c.compare(a, b);
 202     }
 203 
 204     /**
 205      * Checks that the specified object reference is not {@code null}. This
 206      * method is designed primarily for doing parameter validation in methods
 207      * and constructors, as demonstrated below:
 208      * <blockquote><pre>
 209      * public Foo(Bar bar) {
 210      *     this.bar = Objects.requireNonNull(bar);
 211      * }
 212      * </pre></blockquote>
 213      *
 214      * @param obj the object reference to check for nullity
 215      * @param <T> the type of the reference
 216      * @return {@code obj} if not {@code null}
 217      * @throws NullPointerException if {@code obj} is {@code null}
 218      */
 219     public static <T> T requireNonNull(T obj) {
 220         if (obj == null)
 221             throw new NullPointerException();
 222         return obj;
 223     }
 224 
 225     /**
 226      * Checks that the specified object reference is not {@code null} and
 227      * throws a customized {@link NullPointerException} if it is. This method
 228      * is designed primarily for doing parameter validation in methods and
 229      * constructors with multiple parameters, as demonstrated below:
 230      * <blockquote><pre>
 231      * public Foo(Bar bar, Baz baz) {
 232      *     this.bar = Objects.requireNonNull(bar, "bar must not be null");
 233      *     this.baz = Objects.requireNonNull(baz, "baz must not be null");
 234      * }
 235      * </pre></blockquote>
 236      *
 237      * @param obj     the object reference to check for nullity
 238      * @param message detail message to be used in the event that a {@code
 239      *                NullPointerException} is thrown
 240      * @param <T> the type of the reference
 241      * @return {@code obj} if not {@code null}
 242      * @throws NullPointerException if {@code obj} is {@code null}
 243      */
 244     public static <T> T requireNonNull(T obj, String message) {
 245         if (obj == null)
 246             throw new NullPointerException(message);
 247         return obj;
 248     }
 249 
 250     /**
 251      * Returns {@code true} if the provided reference is {@code null} otherwise
 252      * returns {@code false}.
 253      *
 254      * @apiNote This method exists to be used as a
 255      * {@link java.util.function.Predicate}, {@code filter(Objects::isNull)}
 256      *
 257      * @param obj a reference to be checked against {@code null}
 258      * @return {@code true} if the provided reference is {@code null} otherwise
 259      * {@code false}
 260      *
 261      * @see java.util.function.Predicate
 262      * @since 1.8
 263      */
 264     public static boolean isNull(Object obj) {
 265         return obj == null;
 266     }
 267 
 268     /**
 269      * Returns {@code true} if the provided reference is non-{@code null}
 270      * otherwise returns {@code false}.
 271      *
 272      * @apiNote This method exists to be used as a
 273      * {@link java.util.function.Predicate}, {@code filter(Objects::nonNull)}
 274      *
 275      * @param obj a reference to be checked against {@code null}
 276      * @return {@code true} if the provided reference is non-{@code null}
 277      * otherwise {@code false}
 278      *
 279      * @see java.util.function.Predicate
 280      * @since 1.8
 281      */
 282     public static boolean nonNull(Object obj) {
 283         return obj != null;
 284     }
 285 
 286     /**
 287      * Returns the first argument if it is non-{@code null} and
 288      * otherwise returns the non-{@code null} second argument.
 289      *
 290      * @param obj an object
 291      * @param defaultObj a non-{@code null} object to return if the first argument
 292      *                   is {@code null}
 293      * @param <T> the type of the reference
 294      * @return the first argument if it is non-{@code null} and
 295      *        otherwise the second argument if it is non-{@code null}
 296      * @throws NullPointerException if both {@code obj} is null and
 297      *        {@code defaultObj} is {@code null}
 298      * @since 9
 299      */
 300     public static <T> T requireNonNullElse(T obj, T defaultObj) {
 301         return (obj != null) ? obj : requireNonNull(defaultObj, "defaultObj");
 302     }
 303 
 304     /**
 305      * Returns the first argument if it is non-{@code null} and otherwise
 306      * returns the non-{@code null} value of {@code supplier.get()}.
 307      *
 308      * @param obj an object
 309      * @param supplier of a non-{@code null} object to return if the first argument
 310      *                 is {@code null}
 311      * @param <T> the type of the first argument and return type
 312      * @return the first argument if it is non-{@code null} and otherwise
 313      *         the value from {@code supplier.get()} if it is non-{@code null}
 314      * @throws NullPointerException if both {@code obj} is null and
 315      *        either the {@code supplier} is {@code null} or
 316      *        the {@code supplier.get()} value is {@code null}
 317      * @since 9
 318      */
 319     public static <T> T requireNonNullElseGet(T obj, Supplier<? extends T> supplier) {
 320         return (obj != null) ? obj
 321                 : requireNonNull(requireNonNull(supplier, "supplier").get(), "supplier.get()");
 322     }
 323 
 324     /**
 325      * Checks that the specified object reference is not {@code null} and
 326      * throws a customized {@link NullPointerException} if it is.
 327      *
 328      * <p>Unlike the method {@link #requireNonNull(Object, String)},
 329      * this method allows creation of the message to be deferred until
 330      * after the null check is made. While this may confer a
 331      * performance advantage in the non-null case, when deciding to
 332      * call this method care should be taken that the costs of
 333      * creating the message supplier are less than the cost of just
 334      * creating the string message directly.
 335      *
 336      * @param obj     the object reference to check for nullity
 337      * @param messageSupplier supplier of the detail message to be
 338      * used in the event that a {@code NullPointerException} is thrown
 339      * @param <T> the type of the reference
 340      * @return {@code obj} if not {@code null}
 341      * @throws NullPointerException if {@code obj} is {@code null}
 342      * @since 1.8
 343      */
 344     public static <T> T requireNonNull(T obj, Supplier<String> messageSupplier) {
 345         if (obj == null)
 346             throw new NullPointerException(messageSupplier.get());
 347         return obj;
 348     }
 349 
 350     /**






































































































































































 351      * Checks if the {@code index} is within the bounds of the range from
 352      * {@code 0} (inclusive) to {@code length} (exclusive).
 353      *
 354      * <p>The {@code index} is defined to be out-of-bounds if any of the
 355      * following inequalities is true:
 356      * <ul>
 357      *  <li>{@code index < 0}</li>
 358      *  <li>{@code index >= length}</li>
 359      *  <li>{@code length < 0}, which is implied from the former inequalities</li>
 360      * </ul>
 361      *






 362      * @param index the index
 363      * @param length the upper-bound (exclusive) of the range
 364      * @return {@code index} if it is within bounds of the range
 365      * @throws IndexOutOfBoundsException if the {@code index} is out-of-bounds
 366      * @since 9
 367      */
 368     @ForceInline
 369     public static
 370     int checkIndex(int index, int length) {
 371         return Preconditions.checkIndex(index, length, null);



















































 372     }
 373 
 374     /**
 375      * Checks if the sub-range from {@code fromIndex} (inclusive) to
 376      * {@code toIndex} (exclusive) is within the bounds of range from {@code 0}
 377      * (inclusive) to {@code length} (exclusive).
 378      *
 379      * <p>The sub-range is defined to be out-of-bounds if any of the following
 380      * inequalities is true:
 381      * <ul>
 382      *  <li>{@code fromIndex < 0}</li>
 383      *  <li>{@code fromIndex > toIndex}</li>
 384      *  <li>{@code toIndex > length}</li>
 385      *  <li>{@code length < 0}, which is implied from the former inequalities</li>
 386      * </ul>
 387      *






 388      * @param fromIndex the lower-bound (inclusive) of the sub-range
 389      * @param toIndex the upper-bound (exclusive) of the sub-range
 390      * @param length the upper-bound (exclusive) the range
 391      * @return {@code fromIndex} if the sub-range within bounds of the range
 392      * @throws IndexOutOfBoundsException if the sub-range is out-of-bounds
 393      * @since 9
 394      */
 395     public static
 396     int checkFromToIndex(int fromIndex, int toIndex, int length) {
 397         return Preconditions.checkFromToIndex(fromIndex, toIndex, length, null);















































 398     }
 399 
 400     /**
 401      * Checks if the sub-range from {@code fromIndex} (inclusive) to
 402      * {@code fromIndex + size} (exclusive) is within the bounds of range from
 403      * {@code 0} (inclusive) to {@code length} (exclusive).
 404      *
 405      * <p>The sub-range is defined to be out-of-bounds if any of the following
 406      * inequalities is true:
 407      * <ul>
 408      *  <li>{@code fromIndex < 0}</li>
 409      *  <li>{@code size < 0}</li>
 410      *  <li>{@code fromIndex + size > length}, taking into account integer overflow</li>
 411      *  <li>{@code length < 0}, which is implied from the former inequalities</li>
 412      * </ul>
 413      *






 414      * @param fromIndex the lower-bound (inclusive) of the sub-interval
 415      * @param size the size of the sub-range
 416      * @param length the upper-bound (exclusive) of the range
 417      * @return {@code fromIndex} if the sub-range within bounds of the range
 418      * @throws IndexOutOfBoundsException if the sub-range is out-of-bounds
 419      * @since 9
 420      */
 421     public static
 422     int checkFromIndexSize(int fromIndex, int size, int length) {
 423         return Preconditions.checkFromIndexSize(fromIndex, size, length, null);
 424     }
 425 















































 426 }
--- EOF ---