01: // Copyright 2004, 2005 The Apache Software Foundation
02: //
03: // Licensed under the Apache License, Version 2.0 (the "License");
04: // you may not use this file except in compliance with the License.
05: // You may obtain a copy of the License at
06: //
07: // http://www.apache.org/licenses/LICENSE-2.0
08: //
09: // 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: private Defense() {
27: // Prevent instantiation
28: }
29:
30: /**
31: * Check for null parameter when not allowed.
32: *
33: * @throws NullPointerException
34: * if parameter is null (the message indicates the name of the parameter).
35: */
36: public static void notNull(Object parameter, String parameterName) {
37: if (parameter == null)
38: throw new NullPointerException(HiveMindMessages
39: .paramNotNull(parameterName));
40: }
41:
42: /**
43: * Check that a parameter is not null, and assignable to a particular type.
44: *
45: * @throws ClassCastException
46: * if not assignable (with a useable message)
47: */
48:
49: public static void isAssignable(Object parameter,
50: Class expectedType, String parameterName) {
51: Defense.notNull(parameter, parameterName);
52:
53: if (!expectedType.isAssignableFrom(parameter.getClass()))
54: throw new ClassCastException(HiveMindMessages
55: .paramWrongType(parameterName, parameter,
56: expectedType));
57: }
58: }
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