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Java > Open Source Codes > org > apache > hivemind > util > Defense


1 // Copyright 2004, 2005 The Apache Software Foundation
2 //
3 // Licensed under the Apache License, Version 2.0 (the "License");
4 // you may not use this file except in compliance with the License.
5 // You may obtain a copy of the License at
6 //
7 // http://www.apache.org/licenses/LICENSE-2.0
8 //
9 // Unless required by applicable law or agreed to in writing, software
10 // distributed under the License is distributed on an "AS IS" BASIS,
11 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
12 // See the License for the specific language governing permissions and
13 // limitations under the License.
14
15 package org.apache.hivemind.util;
16
17 import org.apache.hivemind.HiveMindMessages;
18
19 /**
20  * Simple utilities for defensive programming.
21  *
22  * @author Howard M. Lewis Ship
23  * @since 1.1
24  */
25 public final class Defense
26 {
27     private Defense()
28     {
29         // Prevent instantiation
30 }
31
32     /**
33      * Check for null parameter when not allowed.
34      *
35      * @throws NullPointerException
36      * if parameter is null (the message indicates the name of the parameter).
37      */
38     public static void notNull(Object JavaDoc parameter, String JavaDoc parameterName)
39     {
40         if (parameter == null)
41             throw new NullPointerException JavaDoc(HiveMindMessages.paramNotNull(parameterName));
42     }
43     
44     /**
45      * Check for null field value when not allowed.
46      *
47      * @throws NullPointerException
48      * if field is null (the message indicates the name of the field).
49      */
50    public static void fieldNotNull(Object JavaDoc value, String JavaDoc fieldName)
51     {
52         if (value == null)
53             throw new NullPointerException JavaDoc(HiveMindMessages.fieldNotNull(fieldName));
54     }
55
56     /**
57      * Check that a parameter is not null, and assignable to a particular type.
58      *
59      * @throws ClassCastException
60      * if not assignable (with a useable message)
61      */
62
63     public static void isAssignable(Object JavaDoc parameter, Class JavaDoc expectedType, String JavaDoc parameterName)
64     {
65         Defense.notNull(parameter, parameterName);
66
67         if (!expectedType.isAssignableFrom(parameter.getClass()))
68             throw new ClassCastException JavaDoc(HiveMindMessages.paramWrongType(
69                     parameterName,
70                     parameter,
71                     expectedType));
72     }
73 }
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