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
033public final class Objects extends ExtraObjectsMethodsForWeb {
034  private Objects() {}
035
036  /**
037   * Determines whether two possibly-null objects are equal. Returns:
038   *
039   * <ul>
040   *   <li>{@code true} if {@code a} and {@code b} are both null.
041   *   <li>{@code true} if {@code a} and {@code b} are both non-null and they are equal according to
042   *       {@link Object#equals(Object)}.
043   *   <li>{@code false} in all other situations.
044   * </ul>
045   *
046   * <p>This assumes that any non-null objects passed to this function conform to the {@code
047   * equals()} contract.
048   *
049   * <p><b>Note:</b> this method is now unnecessary and should be treated as deprecated; use {@link
050   * java.util.Objects#equals} instead.
051   */
052  public static boolean equal(@CheckForNull Object a, @CheckForNull Object b) {
053    return a == b || (a != null && a.equals(b));
054  }
055
056  /**
057   * Generates a hash code for multiple values. The hash code is generated by calling {@link
058   * Arrays#hashCode(Object[])}. Note that array arguments to this method, with the exception of a
059   * single Object array, do not get any special handling; their hash codes are based on identity
060   * and not contents.
061   *
062   * <p>This is useful for implementing {@link Object#hashCode()}. For example, in an object that
063   * has three properties, {@code x}, {@code y}, and {@code z}, one could write:
064   *
065   * <pre>{@code
066   * public int hashCode() {
067   *   return Objects.hashCode(getX(), getY(), getZ());
068   * }
069   * }</pre>
070   *
071   * <p><b>Warning:</b> When a single object is supplied, the returned hash code does not equal the
072   * hash code of that object.
073   *
074   * <p><b>Note:</b> this method is now unnecessary and should be treated as deprecated; use {@link
075   * java.util.Objects#hash} instead.
076   */
077  public static int hashCode(@CheckForNull @Nullable Object... objects) {
078    return Arrays.hashCode(objects);
079  }
080}