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25 
26 package java.lang;
27 
28 /**
29  * Thrown when an application tries to load in a class through its
30  * string name using:
31  * <ul>
32  * <li>The <code>forName</code> method in class <code>Class</code>.
33  * <li>The <code>findSystemClass</code> method in class
34  *     <code>ClassLoader</code> .
35  * <li>The <code>loadClass</code> method in class <code>ClassLoader</code>.
36  * </ul>
37  * <p>
38  * but no definition for the class with the specified name could be found.
39  *
40  * <p>As of release 1.4, this exception has been retrofitted to conform to
41  * the general purpose exception-chaining mechanism.  The "optional exception
42  * that was raised while loading the class" that may be provided at
43  * construction time and accessed via the {@link #getException()} method is
44  * now known as the <i>cause</i>, and may be accessed via the {@link
45  * Throwable#getCause()} method, as well as the aforementioned "legacy method."
46  *
47  * @author  unascribed
48  * @see     java.lang.Class#forName(java.lang.String)
49  * @see     java.lang.ClassLoader#findSystemClass(java.lang.String)
50  * @see     java.lang.ClassLoader#loadClass(java.lang.String, boolean)
51  * @since   JDK1.0
52  */
53 public class ClassNotFoundException extends ReflectiveOperationException {
54     /**
55      * use serialVersionUID from JDK 1.1.X for interoperability
56      */
57      private static final long serialVersionUID = 9176873029745254542L;
58 
59     /**
60      * This field holds the exception ex if the
61      * ClassNotFoundException(String s, Throwable ex) constructor was
62      * used to instantiate the object
63      * @serial
64      * @since 1.2
65      */
66     private Throwable ex;
67 
68     /**
69      * Constructs a <code>ClassNotFoundException</code> with no detail message.
70      */
ClassNotFoundException()71     public ClassNotFoundException() {
72         super((Throwable)null);  // Disallow initCause
73     }
74 
75     /**
76      * Constructs a <code>ClassNotFoundException</code> with the
77      * specified detail message.
78      *
79      * @param   s   the detail message.
80      */
ClassNotFoundException(String s)81     public ClassNotFoundException(String s) {
82         super(s, null);  //  Disallow initCause
83     }
84 
85     /**
86      * Constructs a <code>ClassNotFoundException</code> with the
87      * specified detail message and optional exception that was
88      * raised while loading the class.
89      *
90      * @param s the detail message
91      * @param ex the exception that was raised while loading the class
92      * @since 1.2
93      */
ClassNotFoundException(String s, Throwable ex)94     public ClassNotFoundException(String s, Throwable ex) {
95         super(s, null);  //  Disallow initCause
96         this.ex = ex;
97     }
98 
99     /**
100      * Returns the exception that was raised if an error occurred while
101      * attempting to load the class. Otherwise, returns <tt>null</tt>.
102      *
103      * <p>This method predates the general-purpose exception chaining facility.
104      * The {@link Throwable#getCause()} method is now the preferred means of
105      * obtaining this information.
106      *
107      * @return the <code>Exception</code> that was raised while loading a class
108      * @since 1.2
109      */
getException()110     public Throwable getException() {
111         return ex;
112     }
113 
114     /**
115      * Returns the cause of this exception (the exception that was raised
116      * if an error occurred while attempting to load the class; otherwise
117      * <tt>null</tt>).
118      *
119      * @return  the cause of this exception.
120      * @since   1.4
121      */
getCause()122     public Throwable getCause() {
123         return ex;
124     }
125 }
126