问使用bcel构造方法栈图

EN

public class Insert{
    public static void main(String[] args) throws ClassFormatException, IOException{
        Insert isrt = new Insert();
        String className = "StringBuilder.class";
        JavaClass jclzz = new ClassParser(className).parse();
        ClassGen cgen = new ClassGen(jclzz);
        ConstantPoolGen cpgen = cgen.getConstantPool();
        MethodGen mgen = new MethodGen(jclzz.getMethods()[1], className, cpgen);
        InstructionFactory ifac = new InstructionFactory(cgen);
        InstructionList ilist = mgen.getInstructionList();
        for (InstructionHandle ihandle : ilist.getInstructionHandles()){
            System.out.println(ihandle.toString());
        }
        InstructionFinder f = new InstructionFinder(ilist);
        InstructionHandle[] insert_pos = (InstructionHandle[])(f.search("invokevirtual").next());
        Instruction inserted_inst = ifac.createInvoke("java.lang.System", "currentTimeMillis", Type.LONG, Type.NO_ARGS, Constants.INVOKESTATIC);
        System.out.println(inserted_inst.toString());
        ilist.insert(insert_pos[0], inserted_inst);


        mgen.setMaxStack();
        mgen.setMaxLocals();


        mgen.removeCodeAttributes();
        cgen.replaceMethod(jclzz.getMethods()[1], mgen.getMethod());

        ilist.dispose();
        //output the file
        FileOutputStream fos = new FileOutputStream(className);
        cgen.getJavaClass().dump(fos);
        fos.close();
    }
}