001 /*
002 * $Id: Contract.java,v 1.7 2012/02/19 17:35:52 davep Exp $
003 *
004 * This file is part of McIDAS-V
005 *
006 * Copyright 2007-2012
007 * Space Science and Engineering Center (SSEC)
008 * University of Wisconsin - Madison
009 * 1225 W. Dayton Street, Madison, WI 53706, USA
010 * https://www.ssec.wisc.edu/mcidas
011 *
012 * All Rights Reserved
013 *
014 * McIDAS-V is built on Unidata's IDV and SSEC's VisAD libraries, and
015 * some McIDAS-V source code is based on IDV and VisAD source code.
016 *
017 * McIDAS-V is free software; you can redistribute it and/or modify
018 * it under the terms of the GNU Lesser Public License as published by
019 * the Free Software Foundation; either version 3 of the License, or
020 * (at your option) any later version.
021 *
022 * McIDAS-V is distributed in the hope that it will be useful,
023 * but WITHOUT ANY WARRANTY; without even the implied warranty of
024 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
025 * GNU Lesser Public License for more details.
026 *
027 * You should have received a copy of the GNU Lesser Public License
028 * along with this program. If not, see http://www.gnu.org/licenses.
029 */
030 package edu.wisc.ssec.mcidasv.util;
031
032 import java.util.List;
033
034 /**
035 * This is a {@literal "convenience"} class--use these methods to reduce
036 * boilerplate parameter verification. For example:
037 * <pre>
038 * if (str == null) {
039 * throw new NullPointerException("null is bad");
040 * }</pre>
041 * can be replaced with
042 * <pre>
043 * notNull(str, "null is bad");</pre>
044 *
045 * Remember that these methods are used to signal an error in the <b>calling</b>
046 * method!
047 */
048 public final class Contract {
049 private Contract() { }
050
051 /**
052 * Ensures that a parameter passed to the calling method is not
053 * {@code null}.
054 *
055 * @param object Object to test.
056 *
057 * @return {@code object}, if it is not {@code null}.
058 *
059 * @throws NullPointerException if {@code object} is {@code null}.
060 */
061 public static <T> T notNull(T object) {
062 if (object == null) {
063 throw new NullPointerException();
064 }
065 return object;
066 }
067
068 /**
069 * Ensures that a parameter passed to the calling method is not
070 * {@code null}.
071 *
072 * @param object Object to test.
073 * @param message Exception message to use if {@code object} is
074 * {@code null}.
075 *
076 * @return {@code object}, if it is not {@code null}.
077 *
078 * @throws NullPointerException if {@code object} is {@code null}.
079 */
080 public static <T> T notNull(T object, Object message) {
081 if (object == null) {
082 throw new NullPointerException(String.valueOf(message));
083 }
084 return object;
085 }
086
087 /**
088 * Ensures that a parameter passed to the calling method is not
089 * {@code null}.
090 *
091 * @param object Object to test.
092 * @param format Template used to create an exception if {@code object} is
093 * {@code null}. Uses {@link String#format(String, Object...)}.
094 * @param values Values to use within {@code format}.
095 *
096 * @return {@code object}, if it is not {@code null}.
097 *
098 * @throws NullPointerException if {@code object} is {@code null}.
099 */
100 public static <T> T notNull(T object, String format, Object... values) {
101 if (object == null) {
102 throw new NullPointerException(String.format(format, values));
103 }
104 return object;
105 }
106
107 public static <T> List<T> noNulls(String message, T... objects) {
108 for (T object : objects) {
109 if (object == null) {
110 throw new NullPointerException(message);
111 }
112 }
113 return CollectionHelpers.list(objects);
114 }
115
116 /**
117 * Ensures the {@literal "truth"} of an expression involving parameters
118 * passed to the calling method.
119 *
120 * @param expression A boolean expression to test.
121 *
122 * @throws IllegalArgumentException if {@code expression} is {@code false}.
123 */
124 public static void checkArg(boolean expression) {
125 if (!expression) {
126 throw new IllegalArgumentException();
127 }
128 }
129
130 /**
131 * Ensures the {@literal "truth"} of an expression involving parameters
132 * passed to the calling method.
133 *
134 * @param expression A boolean expression to test.
135 * @param message Exception message to use if {@code expression} is
136 * {@code false}.
137 *
138 * @throws IllegalArgumentException if {@code expression} is {@code false}.
139 */
140 public static void checkArg(boolean expression, Object message) {
141 if (!expression) {
142 throw new IllegalArgumentException(String.valueOf(message));
143 }
144 }
145
146 /**
147 * Ensures the {@literal "truth"} of an expression involving parameters
148 * passed to the calling method.
149 *
150 * @param expression A boolean expression to test.
151 * @param format Template used to create an exception if {@code expression} is
152 * {@code false}. Uses {@link String#format(String, Object...)}.
153 * @param values Values to use within {@code format}.
154 *
155 * @throws IllegalArgumentException if {@code expression} is {@code false}.
156 */
157 public static void checkArg(boolean expression, String format,
158 Object... values)
159 {
160 if (!expression) {
161 throw new IllegalArgumentException(String.format(format, values));
162 }
163 }
164
165 public static void instanceOf(Object object, Class<?> clazz) {
166 if (!clazz.isInstance(object)) {
167 throw new IllegalArgumentException();
168 }
169 }
170
171 public static void instanceOf(Object message, Object object, Class<?> clazz) {
172 if (!clazz.isInstance(object)) {
173 throw new IllegalArgumentException(String.valueOf(message));
174 }
175 }
176
177 public static boolean isInstanceOf(Object object, Class<?> clazz) {
178 notNull(object);
179 notNull(clazz);
180 return clazz.isInstance(object);
181 }
182 }