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.ui.internal.misc;
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      }
30  
31      /** Asserts that an argument is legal. If the given boolean is
32       * not <code>true</code>, an <code>IllegalArgumentException</code>
33       * is thrown.
34       *
35       * @param expression the outcode of the check
36       * @return <code>true</code> if the check passes (does not return
37       *    if the check fails)
38       * @exception IllegalArgumentException if the legality test failed
39       */
40      public static boolean isLegal(boolean expression) {
41          return isLegal(expression, "");//$NON-NLS-1$
42      }
43  
44      /** Asserts that an argument is legal. If the given boolean is
45       * not <code>true</code>, an <code>IllegalArgumentException</code>
46       * is thrown.
47       * The given message is included in that exception, to aid debugging.
48       *
49       * @param expression the outcode of the check
50       * @param message the message to include in the exception
51       * @return <code>true</code> if the check passes (does not return
52       *    if the check fails)
53       * @exception IllegalArgumentException if the legality test failed
54       */
55      public static boolean isLegal(boolean expression, String   message) {
56          if (!expression)
57              throw new IllegalArgumentException  ();
58          return expression;
59      }
60  
61      /** Asserts that the given object is not <code>null</code>. If this
62       * is not the case, some kind of unchecked exception is thrown.
63       * 
64       * @param object the value to test
65       * @exception IllegalArgumentException if the object is <code>null</code>
66       */
67      public static void isNotNull(Object   object) {
68          isNotNull(object, "");//$NON-NLS-1$
69      }
70  
71      /** Asserts that the given object is not <code>null</code>. If this
72       * is not the case, some kind of unchecked exception is thrown.
73       * The given message is included in that exception, to aid debugging.
74       *
75       * @param object the value to test
76       * @param message the message to include in the exception
77       * @exception IllegalArgumentException if the object is <code>null</code>
78       */
79      public static void isNotNull(Object   object, String   message) {
80          if (object == null)
81              throw new AssertionFailedException("null argument;" + message);//$NON-NLS-1$
82      }
83  
84      /** Asserts that the given boolean is <code>true</code>. If this
85       * is not the case, some kind of unchecked exception is thrown.
86       *
87       * @param expression the outcode of the check
88       * @return <code>true</code> if the check passes (does not return
89       *    if the check fails)
90       */
91      public static boolean isTrue(boolean expression) {
92          return isTrue(expression, "");//$NON-NLS-1$
93      }
94  
95      /** Asserts that the given boolean is <code>true</code>. If this
96       * is not the case, some kind of unchecked exception is thrown.
97       * The given message is included in that exception, to aid debugging.
98       *
99       * @param expression the outcode of the check
100      * @param message the message to include in the exception
101      * @return <code>true</code> if the check passes (does not return
102      *    if the check fails)
103      */
104     public static boolean isTrue(boolean expression, String   message) {
105         if (!expression)
106             throw new AssertionFailedException("assertion failed; " + message);//$NON-NLS-1$
107         return expression;
108     }
109 }
110
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