Assert


1   /*******************************************************************************
2    * Copyright (c) 2000, 2004 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.core.internal.runtime;
12  
13  /**
14   * <code>Assert</code> is useful for for embedding runtime sanity checks
15   * in code.
16   * The predicate methods all test a condition and throw some
17   * type of unchecked exception if the condition does not hold.
18   * <p>
19   * Assertion failure exceptions, like most runtime exceptions, are
20   * thrown when something is misbehaving. Assertion failures are invariably
21   * unspecified behavior; consequently, clients should never rely on
22   * these being thrown (and certainly should not being catching them
23   * specifically).
24   * </p>
25   */
26  public final class Assert {
27      /* This class is not intended to be instantiated. */
28      private Assert() {
29          // not allowed
30      }
31  
32      /** Asserts that an argument is legal. If the given boolean is
33       * not <code>true</code>, an <code>IllegalArgumentException</code>
34       * is thrown.
35       *
36       * @param expression the outcode of the check
37       * @return <code>true</code> if the check passes (does not return
38       *    if the check fails)
39       * @exception IllegalArgumentException if the legality test failed
40       */
41      public static boolean isLegal(boolean expression) {
42          return isLegal(expression, ""); //$NON-NLS-1$
43      }
44  
45      /** Asserts that an argument is legal. If the given boolean is
46       * not <code>true</code>, an <code>IllegalArgumentException</code>
47       * is thrown.
48       * The given message is included in that exception, to aid debugging.
49       *
50       * @param expression the outcode of the check
51       * @param message the message to include in the exception
52       * @return <code>true</code> if the check passes (does not return
53       *    if the check fails)
54       * @exception IllegalArgumentException if the legality test failed
55       */
56      public static boolean isLegal(boolean expression, String   message) {
57          if (!expression)
58              throw new IllegalArgumentException  (message);
59          return expression;
60      }
61  
62      /** Asserts that the given object is not <code>null</code>. If this
63       * is not the case, some kind of unchecked exception is thrown.
64       * 
65       * @param object the value to test
66       * @exception IllegalArgumentException if the object is <code>null</code>
67       */
68      public static void isNotNull(Object   object) {
69          isNotNull(object, ""); //$NON-NLS-1$
70      }
71  
72      /** Asserts that the given object is not <code>null</code>. If this
73       * is not the case, some kind of unchecked exception is thrown.
74       * The given message is included in that exception, to aid debugging.
75       *
76       * @param object the value to test
77       * @param message the message to include in the exception
78       * @exception IllegalArgumentException if the object is <code>null</code>
79       */
80      public static void isNotNull(Object   object, String   message) {
81          if (object == null)
82              throw new AssertionFailedException("null argument:" + message); //$NON-NLS-1$
83      }
84  
85      /** Asserts that the given boolean is <code>true</code>. If this
86       * is not the case, some kind of unchecked exception is thrown.
87       *
88       * @param expression the outcode of the check
89       * @return <code>true</code> if the check passes (does not return
90       *    if the check fails)
91       */
92      public static boolean isTrue(boolean expression) {
93          return isTrue(expression, ""); //$NON-NLS-1$
94      }
95  
96      /** Asserts that the given boolean is <code>true</code>. If this
97       * is not the case, some kind of unchecked exception is thrown.
98       * The given message is included in that exception, to aid debugging.
99       *
100      * @param expression the outcode of the check
101      * @param message the message to include in the exception
102      * @return <code>true</code> if the check passes (does not return
103      *    if the check fails)
104      */
105     public static boolean isTrue(boolean expression, String   message) {
106         if (!expression)
107             throw new AssertionFailedException("assertion failed: " + message); //$NON-NLS-1$
108         return expression;
109     }
110 }
111
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