001/*
002 * Copyright (C) 2007 The Guava Authors
003 *
004 * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
005 * in compliance with the License. You may obtain a copy of the License at
006 *
007 * http://www.apache.org/licenses/LICENSE-2.0
008 *
009 * Unless required by applicable law or agreed to in writing, software distributed under the License
010 * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
011 * or implied. See the License for the specific language governing permissions and limitations under
012 * the License.
013 */
014
015package com.google.common.base;
016
017import com.google.common.annotations.GwtCompatible;
018import java.util.Arrays;
019import javax.annotation.CheckForNull;
020import org.checkerframework.checker.nullness.qual.Nullable;
021
022/**
023 * Helper functions that can operate on any {@code Object}.
024 *
025 * <p>See the Guava User Guide on <a
026 * href="https://github.com/google/guava/wiki/CommonObjectUtilitiesExplained">writing {@code Object}
027 * methods with {@code Objects}</a>.
028 *
029 * @author Laurence Gonsalves
030 * @since 2.0
031 */
032@GwtCompatible
033@ElementTypesAreNonnullByDefault
034public final class Objects extends ExtraObjectsMethodsForWeb {
035  private Objects() {}
036
037  /**
038   * Determines whether two possibly-null objects are equal. Returns:
039   *
040   * <ul>
041   *   <li>{@code true} if {@code a} and {@code b} are both null.
042   *   <li>{@code true} if {@code a} and {@code b} are both non-null and they are equal according to
043   *       {@link Object#equals(Object)}.
044   *   <li>{@code false} in all other situations.
045   * </ul>
046   *
047   * <p>This assumes that any non-null objects passed to this function conform to the {@code
048   * equals()} contract.
049   *
050   * <p><b>Note for Java 7 and later:</b> This method should be treated as deprecated; use {@link
051   * java.util.Objects#equals} instead.
052   */
053  public static boolean equal(@CheckForNull Object a, @CheckForNull Object b) {
054    return a == b || (a != null && a.equals(b));
055  }
056
057  /**
058   * Generates a hash code for multiple values. The hash code is generated by calling {@link
059   * Arrays#hashCode(Object[])}. Note that array arguments to this method, with the exception of a
060   * single Object array, do not get any special handling; their hash codes are based on identity
061   * and not contents.
062   *
063   * <p>This is useful for implementing {@link Object#hashCode()}. For example, in an object that
064   * has three properties, {@code x}, {@code y}, and {@code z}, one could write:
065   *
066   * <pre>{@code
067   * public int hashCode() {
068   *   return Objects.hashCode(getX(), getY(), getZ());
069   * }
070   * }</pre>
071   *
072   * <p><b>Warning:</b> When a single object is supplied, the returned hash code does not equal the
073   * hash code of that object.
074   *
075   * <p><b>Note for Java 7 and later:</b> This method should be treated as deprecated; use {@link
076   * java.util.Objects#hash} instead.
077   */
078  public static int hashCode(@CheckForNull @Nullable Object... objects) {
079    return Arrays.hashCode(objects);
080  }
081}