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 the original author or authors. 014 */ 015 package org.fest.util; 016 017 import static org.fest.util.Arrays.isEmpty; 018 019 /** 020 * Understands utility methods related to objects. 021 * 022 * @author Alex Ruiz 023 */ 024 public final class Objects { 025 026 /** Prime number used to calculate the hash code of objects. */ 027 public static final int HASH_CODE_PRIME = 31; 028 029 /** 030 * Returns <code>true</code> if the given objects are equal or if both objects are <code>null</code>. 031 * @param o1 one of the objects to compare. 032 * @param o2 one of the objects to compare. 033 * @return <code>true</code> if the given objects are equal or if both objects are <code>null</code>. 034 */ 035 public static boolean areEqual(Object o1, Object o2) { 036 if (o1 == null) return o2 == null; 037 return o1.equals(o2); 038 } 039 040 /** 041 * Returns an array containing the names of the given types. 042 * @param types the given types. 043 * @return the names of the given types stored in an array. 044 */ 045 public static String[] namesOf(Class<?>... types) { 046 if (isEmpty(types)) return new String[0]; 047 String[] names = new String[types.length]; 048 for (int i = 0; i < types.length; i++) names[i] = types[i].getName(); 049 return names; 050 } 051 052 /** 053 * Returns the hash code for the given object. If the object is <code>null</code>, this method returns zero. Otherwise 054 * calls the method <code>hashCode</code> of the given object. 055 * @param o the given object. 056 * @return the hash code for the given object 057 */ 058 public static int hashCodeFor(Object o) { 059 return o != null ? o.hashCode() : 0; 060 } 061 062 /** 063 * 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 064 * type, this method returns <code>null</code>. 065 * @param <T> the generic type to cast the given object to. 066 * @param o the object to cast. 067 * @param type the given type. 068 * @return the casted object, or <code>null</code> if the given object is not to the given type. 069 */ 070 public static <T> T castIfBelongsToType(Object o, Class<T> type) { 071 if (o != null && type.isAssignableFrom(o.getClass())) return type.cast(o); 072 return null; 073 } 074 075 private Objects() {} 076 }