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
015package org.apache.hivemind.util;
016
017import org.apache.hivemind.HiveMindMessages;
018
019/**
020 * Simple utilities for defensive programming.
021 * 
022 * @author Howard M. Lewis Ship
023 * @since 1.1
024 */
025public 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}