Assert


1   /*******************************************************************************
2    * Copyright (c) 2000, 2006 IBM Corporation and others.
3    * All rights reserved. This program and the accompanying materials
4    * are made available under the terms of the Eclipse Public License v1.0
5    * which accompanies this distribution, and is available at
6    * http://www.eclipse.org/legal/epl-v10.html
7    *
8    * Contributors:
9    *     IBM Corporation - initial API and implementation
10   *******************************************************************************/
11  package org.eclipse.jface.util;
12  
13  /**
14   * <code>Assert</code> is useful for for embedding runtime sanity checks
15   * in code. The static predicate methods all test a condition and throw some
16   * type of unchecked exception if the condition does not hold.
17   * <p>
18   * Assertion failure exceptions, like most runtime exceptions, are
19   * thrown when something is misbehaving. Assertion failures are invariably
20   * unspecified behavior; consequently, clients should never rely on
21   * these being thrown (or not thrown). <b>If you find yourself in the
22   * position where you need to catch an assertion failure, you have most 
23   * certainly written your program incorrectly.</b>
24   * </p>
25   * <p>
26   * Note that an <code>assert</code> statement is slated to be added to the
27   * Java language in JDK 1.4, rending this class obsolete.
28   * 
29   * @deprecated As of 3.3, replaced by {@link org.eclipse.core.runtime.Assert}
30   * </p>
31   */
32  public final class Assert {
33  
34      /**
35       * <code>AssertionFailedException</code> is a runtime exception thrown
36       * by some of the methods in <code>Assert</code>.
37       * <p>
38       * This class is not declared public to prevent some misuses; programs that catch 
39       * or otherwise depend on assertion failures are susceptible to unexpected
40       * breakage when assertions in the code are added or removed.
41       * </p>
42       */
43      private static class AssertionFailedException extends RuntimeException   {
44  
45          /**
46           * Generated serial version UID for this class.
47           * @since 3.1
48           */
49          private static final long serialVersionUID = 3257852073508024376L;
50  
51          /**
52           * Constructs a new exception.
53           */
54          public AssertionFailedException() {
55          }
56  
57          /**
58           * Constructs a new exception with the given message.
59           * @param detail the detail message
60           */
61          public AssertionFailedException(String   detail) {
62              super(detail);
63          }
64      }
65  
66      /* This class is not intended to be instantiated. */
67      private Assert() {
68      }
69  
70      /**
71       * Asserts that an argument is legal. If the given boolean is
72       * not <code>true</code>, an <code>IllegalArgumentException</code>
73       * is thrown.
74       *
75       * @param expression the outcome of the check
76       * @return <code>true</code> if the check passes (does not return
77       *    if the check fails)
78       * @exception IllegalArgumentException if the legality test failed
79       */
80      public static boolean isLegal(boolean expression) {
81          // succeed as quickly as possible
82          if (expression) {
83              return true;
84          }
85          return isLegal(expression, "");//$NON-NLS-1$
86      }
87  
88      /**
89       * Asserts that an argument is legal. If the given boolean is
90       * not <code>true</code>, an <code>IllegalArgumentException</code>
91       * is thrown.
92       * The given message is included in that exception, to aid debugging.
93       *
94       * @param expression the outcome of the check
95       * @param message the message to include in the exception
96       * @return <code>true</code> if the check passes (does not return
97       *    if the check fails)
98       * @exception IllegalArgumentException if the legality test failed
99       */
100     public static boolean isLegal(boolean expression, String   message) {
101         if (!expression) {
102             throw new IllegalArgumentException  ("assertion failed; " + message); //$NON-NLS-1$
103         }
104         return expression;
105     }
106 
107     /**
108      * Asserts that the given object is not <code>null</code>. If this
109      * is not the case, some kind of unchecked exception is thrown.
110      * <p>
111      * As a general rule, parameters passed to API methods must not be
112      * <code>null</code> unless <b>explicitly</b> allowed in the method's
113      * specification. Similarly, results returned from API methods are never
114      * <code>null</code> unless <b>explicitly</b> allowed in the method's
115      * specification. Implementations are encouraged to make regular use of 
116      * <code>Assert.isNotNull</code> to ensure that <code>null</code> 
117      * parameters are detected as early as possible.
118      * </p>
119      * 
120      * @param object the value to test
121      * @exception AssertionFailedException an unspecified unchecked exception if the object
122      *   is <code>null</code>
123      */
124     public static void isNotNull(Object   object) {
125         // succeed as quickly as possible
126         if (object != null) {
127             return;
128         }
129         isNotNull(object, "");//$NON-NLS-1$
130     }
131 
132     /**
133      * Asserts that the given object is not <code>null</code>. If this
134      * is not the case, some kind of unchecked exception is thrown.
135      * The given message is included in that exception, to aid debugging.
136      * <p>
137      * As a general rule, parameters passed to API methods must not be
138      * <code>null</code> unless <b>explicitly</b> allowed in the method's
139      * specification. Similarly, results returned from API methods are never
140      * <code>null</code> unless <b>explicitly</b> allowed in the method's
141      * specification. Implementations are encouraged to make regular use of 
142      * <code>Assert.isNotNull</code> to ensure that <code>null</code> 
143      * parameters are detected as early as possible.
144      * </p>
145      * 
146      * @param object the value to test
147      * @param message the message to include in the exception
148      * @exception AssertionFailedException an unspecified unchecked exception if the object
149      *   is <code>null</code>
150      */
151     public static void isNotNull(Object   object, String   message) {
152         if (object == null) {
153             throw new AssertionFailedException("null argument;" + message);//$NON-NLS-1$
154         }
155     }
156 
157     /**
158      * Asserts that the given boolean is <code>true</code>. If this
159      * is not the case, some kind of unchecked exception is thrown.
160      *
161      * @param expression the outcome of the check
162      * @return <code>true</code> if the check passes (does not return
163      *    if the check fails)
164      */
165     public static boolean isTrue(boolean expression) {
166         // succeed as quickly as possible
167         if (expression) {
168             return true;
169         }
170         return isTrue(expression, "");//$NON-NLS-1$
171     }
172 
173     /**
174      * Asserts that the given boolean is <code>true</code>. If this
175      * is not the case, some kind of unchecked exception is thrown.
176      * The given message is included in that exception, to aid debugging.
177      *
178      * @param expression the outcome of the check
179      * @param message the message to include in the exception
180      * @return <code>true</code> if the check passes (does not return
181      *    if the check fails)
182      */
183     public static boolean isTrue(boolean expression, String   message) {
184         if (!expression) {
185             throw new AssertionFailedException("Assertion failed: " + message);//$NON-NLS-1$
186         }
187         return expression;
188     }
189 }
190
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