1 /* 2 * Copyright 2009 Sun Microsystems, Inc. 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. Sun designates this 8 * particular file as subject to the "Classpath" exception as provided 9 * by Sun 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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara, 22 * CA 95054 USA or visit www.sun.com if you need additional information or 23 * have any questions. 24 */ 25 26 package java.util; 27 28 /** 29 * This class consists of {@code static} utility methods for operating 30 * on objects. These utilities include {@code null}-safe or {@code 31 * null}-tolerant methods for computing the hash code of an object, 32 * returning a string for an object, and comparing two objects. 33 * 34 * @since 1.7 35 */ 36 public class Objects { 37 private Objects() { 38 throw new AssertionError("No java.util.Objects instances for you!"); 39 } 40 41 /** 42 * Returns {@code true} if the arguments are equal to each other 43 * and {@code false} otherwise. 44 * Consequently, if both arguments are {@code null}, {@code true} 45 * is returned and if exactly one argument is {@code null}, {@code 46 * false} is returned. Otherwise, equality is determined by using 47 * the {@link Object#equals equals} method of the first 48 * argument. 49 * 50 * @return {@code true} if the arguments are equal to each other 51 * and {@code false} otherwise 52 * @see Object#equals(Object) 53 */ 54 public static boolean equals(Object a, Object b) { 55 return (a == b) || (a != null && a.equals(b)); 56 } 57 58 /** 59 * Returns the hash code of a non-{@code null} argument and 0 for 60 * a {@code null} argument. 61 * 62 * @return the hash code of a non-{@code null} argument and 0 for 63 * a {@code null} argument 64 * @see Object#hashCode 65 */ 66 public static int hashCode(Object o) { 67 return o != null ? o.hashCode() : 0; 68 } 69 70 /** 71 * Returns the result of calling {@code toString} for a non-{@code 72 * null} argument and {@code "null"} for a {@code null} argument. 73 * 74 * @return the result of calling {@code toString} for a non-{@code 75 * null} argument and {@code "null"} for a {@code null} argument 76 * @see Object#toString 77 * @see String#valueOf(Object) 78 */ 79 public static String toString(Object o) { 80 return String.valueOf(o); 81 } 82 83 /** 84 * Returns 0 if the arguments are identical and {@code 85 * c.compare(a, b)} otherwise. 86 * Consequently, if both arguments are {@code null} 0 87 * is returned. 88 * 89 * <p>Note that if one of the arguments is {@code null}, a {@code 90 * NullPointerException} may or may not be thrown depending on 91 * what ordering policy, if any, the {@link Comparator Comparator} 92 * chooses to have for {@code null} values. 93 * 94 * @return 0 if the arguments are identical and {@code 95 * c.compare(a, b)} otherwise. 96 * @see Comparable 97 * @see Comparator 98 */ 99 public static <T> int compare(T a, T b, Comparator<? super T> c) { 100 return (a == b) ? 0 : c.compare(a, b); 101 } 102 }