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- package sample;
-
- import javassist.*;
-
- /*
- A very simple sample program
-
- This program overwrites sample/Test.class (the class file of this
- class itself) for adding a method g(). If the method g() is not
- defined in class Test, then this program adds a copy of
- f() to the class Test with name g(). Otherwise, this program does
- not modify sample/Test.class at all.
-
- To see the modified class definition, execute:
-
- % javap sample.Test
-
- after running this program.
- */
- public class Test {
- public int f(int i) {
- return i + 1;
- }
-
- public static void main(String[] args) throws Exception {
- ClassPool pool = ClassPool.getDefault();
-
- CtClass cc = pool.get("sample.Test");
- try {
- cc.getDeclaredMethod("g");
- System.out.println("g() is already defined in sample.Test.");
- }
- catch (NotFoundException e) {
- /* getDeclaredMethod() throws an exception if g()
- * is not defined in sample.Test.
- */
- CtMethod fMethod = cc.getDeclaredMethod("f");
- CtMethod gMethod = CtNewMethod.copy(fMethod, "g", cc, null);
- cc.addMethod(gMethod);
- pool.writeFile("sample.Test"); // update the class file
- System.out.println("g() was added.");
- }
- }
- }
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