001 /*
002 * This file is part of McIDAS-V
003 *
004 * Copyright 2007-2013
005 * Space Science and Engineering Center (SSEC)
006 * University of Wisconsin - Madison
007 * 1225 W. Dayton Street, Madison, WI 53706, USA
008 * https://www.ssec.wisc.edu/mcidas
009 *
010 * All Rights Reserved
011 *
012 * McIDAS-V is built on Unidata's IDV and SSEC's VisAD libraries, and
013 * some McIDAS-V source code is based on IDV and VisAD source code.
014 *
015 * McIDAS-V is free software; you can redistribute it and/or modify
016 * it under the terms of the GNU Lesser Public License as published by
017 * the Free Software Foundation; either version 3 of the License, or
018 * (at your option) any later version.
019 *
020 * McIDAS-V is distributed in the hope that it will be useful,
021 * but WITHOUT ANY WARRANTY; without even the implied warranty of
022 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
023 * GNU Lesser Public License for more details.
024 *
025 * You should have received a copy of the GNU Lesser Public License
026 * along with this program. If not, see http://www.gnu.org/licenses.
027 */
028 package edu.wisc.ssec.mcidasv.util;
029
030 import java.util.List;
031
032 /**
033 * This is a {@literal "convenience"} class--use these methods to reduce
034 * boilerplate parameter verification. For example:
035 * <pre>
036 * if (str == null) {
037 * throw new NullPointerException("null is bad");
038 * }</pre>
039 * can be replaced with
040 * <pre>
041 * notNull(str, "null is bad");</pre>
042 *
043 * Remember that these methods are used to signal an error in the <b>calling</b>
044 * method!
045 */
046 public final class Contract {
047 private Contract() { }
048
049 /**
050 * Ensures that a parameter passed to the calling method is not
051 * {@code null}.
052 *
053 * @param object Object to test.
054 *
055 * @return {@code object}, if it is not {@code null}.
056 *
057 * @throws NullPointerException if {@code object} is {@code null}.
058 */
059 public static <T> T notNull(T object) {
060 if (object == null) {
061 throw new NullPointerException();
062 }
063 return object;
064 }
065
066 /**
067 * Ensures that a parameter passed to the calling method is not
068 * {@code null}.
069 *
070 * @param object Object to test.
071 * @param message Exception message to use if {@code object} is
072 * {@code null}.
073 *
074 * @return {@code object}, if it is not {@code null}.
075 *
076 * @throws NullPointerException if {@code object} is {@code null}.
077 */
078 public static <T> T notNull(T object, Object message) {
079 if (object == null) {
080 throw new NullPointerException(String.valueOf(message));
081 }
082 return object;
083 }
084
085 /**
086 * Ensures that a parameter passed to the calling method is not
087 * {@code null}.
088 *
089 * @param object Object to test.
090 * @param format Template used to create an exception if {@code object} is
091 * {@code null}. Uses {@link String#format(String, Object...)}.
092 * @param values Values to use within {@code format}.
093 *
094 * @return {@code object}, if it is not {@code null}.
095 *
096 * @throws NullPointerException if {@code object} is {@code null}.
097 */
098 public static <T> T notNull(T object, String format, Object... values) {
099 if (object == null) {
100 throw new NullPointerException(String.format(format, values));
101 }
102 return object;
103 }
104
105 public static <T> List<T> noNulls(String message, T... objects) {
106 for (T object : objects) {
107 if (object == null) {
108 throw new NullPointerException(message);
109 }
110 }
111 return CollectionHelpers.list(objects);
112 }
113
114 /**
115 * Ensures the {@literal "truth"} of an expression involving parameters
116 * passed to the calling method.
117 *
118 * @param expression A boolean expression to test.
119 *
120 * @throws IllegalArgumentException if {@code expression} is {@code false}.
121 */
122 public static void checkArg(boolean expression) {
123 if (!expression) {
124 throw new IllegalArgumentException();
125 }
126 }
127
128 /**
129 * Ensures the {@literal "truth"} of an expression involving parameters
130 * passed to the calling method.
131 *
132 * @param expression A boolean expression to test.
133 * @param message Exception message to use if {@code expression} is
134 * {@code false}.
135 *
136 * @throws IllegalArgumentException if {@code expression} is {@code false}.
137 */
138 public static void checkArg(boolean expression, Object message) {
139 if (!expression) {
140 throw new IllegalArgumentException(String.valueOf(message));
141 }
142 }
143
144 /**
145 * Ensures the {@literal "truth"} of an expression involving parameters
146 * passed to the calling method.
147 *
148 * @param expression A boolean expression to test.
149 * @param format Template used to create an exception if {@code expression} is
150 * {@code false}. Uses {@link String#format(String, Object...)}.
151 * @param values Values to use within {@code format}.
152 *
153 * @throws IllegalArgumentException if {@code expression} is {@code false}.
154 */
155 public static void checkArg(boolean expression, String format,
156 Object... values)
157 {
158 if (!expression) {
159 throw new IllegalArgumentException(String.format(format, values));
160 }
161 }
162
163 public static void instanceOf(Object object, Class<?> clazz) {
164 if (!clazz.isInstance(object)) {
165 throw new IllegalArgumentException();
166 }
167 }
168
169 public static void instanceOf(Object message, Object object, Class<?> clazz) {
170 if (!clazz.isInstance(object)) {
171 throw new IllegalArgumentException(String.valueOf(message));
172 }
173 }
174
175 public static boolean isInstanceOf(Object object, Class<?> clazz) {
176 notNull(object);
177 notNull(clazz);
178 return clazz.isInstance(object);
179 }
180 }