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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);
cc.writeFile(); // update the class file
System.out.println("g() was added.");
}
}
}
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