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 }