1 /*
2 * Copyright (C) 2007 The Guava Authors
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
5 * in compliance with the License. You may obtain a copy of the License at
6 *
7 * http://www.apache.org/licenses/LICENSE-2.0
8 *
9 * Unless required by applicable law or agreed to in writing, software distributed under the License
10 * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
11 * or implied. See the License for the specific language governing permissions and limitations under
12 * the License.
13 */
14
15 package com.google.common.base;
16
17 import com.google.common.annotations.GwtCompatible;
18 import java.util.Arrays;
19 import javax.annotation.CheckForNull;
20 import org.checkerframework.checker.nullness.qual.Nullable;
21
22 /**
23 * Helper functions that can operate on any {@code Object}.
24 *
25 * <p>See the Guava User Guide on <a
26 * href="https://github.com/google/guava/wiki/CommonObjectUtilitiesExplained">writing {@code Object}
27 * methods with {@code Objects}</a>.
28 *
29 * @author Laurence Gonsalves
30 * @since 2.0
31 */
32 @GwtCompatible
33 @ElementTypesAreNonnullByDefault
34 public final class Objects extends ExtraObjectsMethodsForWeb {
35 private Objects() {}
36
37 /**
38 * Determines whether two possibly-null objects are equal. Returns:
39 *
40 * <ul>
41 * <li>{@code true} if {@code a} and {@code b} are both null.
42 * <li>{@code true} if {@code a} and {@code b} are both non-null and they are equal according to
43 * {@link Object#equals(Object)}.
44 * <li>{@code false} in all other situations.
45 * </ul>
46 *
47 * <p>This assumes that any non-null objects passed to this function conform to the {@code
48 * equals()} contract.
49 *
50 * <p><b>Note for Java 7 and later:</b> This method should be treated as deprecated; use {@link
51 * java.util.Objects#equals} instead.
52 */
53 public static boolean equal(@CheckForNull Object a, @CheckForNull Object b) {
54 return a == b || (a != null && a.equals(b));
55 }
56
57 /**
58 * Generates a hash code for multiple values. The hash code is generated by calling {@link
59 * Arrays#hashCode(Object[])}. Note that array arguments to this method, with the exception of a
60 * single Object array, do not get any special handling; their hash codes are based on identity
61 * and not contents.
62 *
63 * <p>This is useful for implementing {@link Object#hashCode()}. For example, in an object that
64 * has three properties, {@code x}, {@code y}, and {@code z}, one could write:
65 *
66 * <pre>{@code
67 * public int hashCode() {
68 * return Objects.hashCode(getX(), getY(), getZ());
69 * }
70 * }</pre>
71 *
72 * <p><b>Warning:</b> When a single object is supplied, the returned hash code does not equal the
73 * hash code of that object.
74 *
75 * <p><b>Note for Java 7 and later:</b> This method should be treated as deprecated; use {@link
76 * java.util.Objects#hash} instead.
77 */
78 public static int hashCode(@CheckForNull @Nullable Object... objects) {
79 return Arrays.hashCode(objects);
80 }
81 }