001 // Copyright 2004, 2005 The Apache Software Foundation 002 // 003 // Licensed under the Apache License, Version 2.0 (the "License"); 004 // you may not use this file except in compliance with the License. 005 // 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 010 // distributed under the License is distributed on an "AS IS" BASIS, 011 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 012 // See the License for the specific language governing permissions and 013 // limitations under the License. 014 015 package org.apache.hivemind.util; 016 017 import org.apache.hivemind.HiveMindMessages; 018 019 /** 020 * Simple utilities for defensive programming. 021 * 022 * @author Howard M. Lewis Ship 023 * @since 1.1 024 */ 025 public final class Defense 026 { 027 private Defense() 028 { 029 // Prevent instantiation 030 } 031 032 /** 033 * Check for null parameter when not allowed. 034 * 035 * @throws NullPointerException 036 * if parameter is null (the message indicates the name of the parameter). 037 */ 038 public static void notNull(Object parameter, String parameterName) 039 { 040 if (parameter == null) 041 throw new NullPointerException(HiveMindMessages.paramNotNull(parameterName)); 042 } 043 044 /** 045 * Check that a parameter is not null, and assignable to a particular type. 046 * 047 * @throws ClassCastException 048 * if not assignable (with a useable message) 049 */ 050 051 public static void isAssignable(Object parameter, Class expectedType, String parameterName) 052 { 053 Defense.notNull(parameter, parameterName); 054 055 if (!expectedType.isAssignableFrom(parameter.getClass())) 056 throw new ClassCastException(HiveMindMessages.paramWrongType( 057 parameterName, 058 parameter, 059 expectedType)); 060 } 061 }