001 /*
002 * Created on Jun 2, 2006
003 *
004 * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with
005 * 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 is distributed on
010 * an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the
011 * specific language governing permissions and limitations under the License.
012 *
013 * Copyright @2006-2011 the original author or authors.
014 */
015 package org.fest.util;
016
017 import static org.fest.util.Arrays.*;
018
019 import java.lang.reflect.Array;
020
021 /**
022 * Utility methods related to objects.
023 *
024 * @author Alex Ruiz
025 * @author Joel Costigliola
026 */
027 public final class Objects {
028
029 /** Prime number used to calculate the hash code of objects. */
030 public static final int HASH_CODE_PRIME = 31;
031
032 /**
033 * Returns {@code true} if the given objects are equal or if both objects are {@code null}.
034 * @param o1 one of the objects to compare.
035 * @param o2 one of the objects to compare.
036 * @return {@code true} if the given objects are equal or if both objects are {@code null}.
037 */
038 public static boolean areEqual(Object o1, Object o2) {
039 if (o1 == null) return o2 == null;
040 if (o1.equals(o2)) return true;
041 return areEqualArrays(o1, o2);
042 }
043
044 private static boolean areEqualArrays(Object o1, Object o2) {
045 if (!isArray(o1) || !isArray(o2)) return false;
046 if (o1 == o2) return true;
047 int size = Array.getLength(o1);
048 if (Array.getLength(o2) != size) return false;
049 for (int i = 0; i < size; i++) {
050 Object e1 = Array.get(o1, i);
051 Object e2 = Array.get(o2, i);
052 if (!areEqual(e1, e2)) return false;
053 }
054 return true;
055 }
056
057 /**
058 * Returns an array containing the names of the given types.
059 * @param types the given types.
060 * @return the names of the given types stored in an array.
061 */
062 public static String[] namesOf(Class<?>... types) {
063 if (isEmpty(types)) return new String[0];
064 String[] names = new String[types.length];
065 for (int i = 0; i < types.length; i++)
066 names[i] = types[i].getName();
067 return names;
068 }
069
070 /**
071 * Returns the hash code for the given object. If the object is {@code null}, this method returns zero. Otherwise
072 * calls the method {@code hashCode} of the given object.
073 * @param o the given object.
074 * @return the hash code for the given object
075 */
076 public static int hashCodeFor(Object o) {
077 return o != null ? o.hashCode() : 0;
078 }
079
080 /**
081 * Casts the given object to the given type only if the object is of the given type. If the object is not of the given
082 * type, this method returns {@code null}.
083 * @param <T> the generic type to cast the given object to.
084 * @param o the object to cast.
085 * @param type the given type.
086 * @return the casted object, or {@code null} if the given object is not to the given type.
087 */
088 public static <T> T castIfBelongsToType(Object o, Class<T> type) {
089 if (o != null && type.isAssignableFrom(o.getClass())) return type.cast(o);
090 return null;
091 }
092
093 private Objects() {}
094 }