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.ltk.internal.ui.refactoring;
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      
28      /* This class is not intended to be instantiated. */
29      private Assert() {
30          // not allowed
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      /** 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  (message);
58          return expression;
59      }
60      /** Asserts that the given object is not <code>null</code>. If this
61       * is not the case, some kind of unchecked exception is thrown.
62       * 
63       * @param object the value to test
64       * @exception IllegalArgumentException if the object is <code>null</code>
65       */
66      public static void isNotNull(Object   object) {
67          isNotNull(object, ""); //$NON-NLS-1$
68      }
69      /** Asserts that the given object is not <code>null</code>. If this
70       * is not the case, some kind of unchecked exception is thrown.
71       * The given message is included in that exception, to aid debugging.
72       *
73       * @param object the value to test
74       * @param message the message to include in the exception
75       * @exception IllegalArgumentException if the object is <code>null</code>
76       */
77      public static void isNotNull(Object   object, String   message) {
78          if (object == null)
79              throw new AssertionFailedException("null argument:" + message); //$NON-NLS-1$
80      }
81      /** Asserts that the given boolean is <code>true</code>. If this
82       * is not the case, some kind of unchecked exception is thrown.
83       *
84       * @param expression the outcode of the check
85       * @return <code>true</code> if the check passes (does not return
86       *    if the check fails)
87       */
88      public static boolean isTrue(boolean expression) {
89          return isTrue(expression, ""); //$NON-NLS-1$
90      }
91      /** Asserts that the given boolean is <code>true</code>. If this
92       * is not the case, some kind of unchecked exception is thrown.
93       * The given message is included in that exception, to aid debugging.
94       *
95       * @param expression the outcode of the check
96       * @param message the message to include in the exception
97       * @return <code>true</code> if the check passes (does not return
98       *    if the check fails)
99       */
100     public static boolean isTrue(boolean expression, String   message) {
101         if (!expression)
102             throw new AssertionFailedException("assertion failed: " + message); //$NON-NLS-1$
103         return expression;
104     }
105 }
106
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