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Java > Open Source Codes > sample > Test


1 package sample;
2
3 import javassist.*;
4
5 /*
6    A very simple sample program
7
8    This program overwrites sample/Test.class (the class file of this
9    class itself) for adding a method g(). If the method g() is not
10    defined in class Test, then this program adds a copy of
11    f() to the class Test with name g(). Otherwise, this program does
12    not modify sample/Test.class at all.
13
14    To see the modified class definition, execute:
15
16    % javap sample.Test
17
18    after running this program.
19 */
20 public class Test {
21     public int f(int i) {
22     return i + 1;
23     }
24
25     public static void main(String JavaDoc[] args) throws Exception JavaDoc {
26     ClassPool pool = ClassPool.getDefault();
27
28     CtClass cc = pool.get("sample.Test");
29     try {
30         cc.getDeclaredMethod("g");
31         System.out.println("g() is already defined in sample.Test.");
32     }
33     catch (NotFoundException e) {
34         /* getDeclaredMethod() throws an exception if g()
35          * is not defined in sample.Test.
36          */
37         CtMethod fMethod = cc.getDeclaredMethod("f");
38         CtMethod gMethod = CtNewMethod.copy(fMethod, "g", cc, null);
39         cc.addMethod(gMethod);
40         cc.writeFile(); // update the class file
41 System.out.println("g() was added.");
42     }
43     }
44 }
45
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