#vulnerable code 
                                public void renameClass(String oldName, String newName) {
        LongVector v = items;
        int size = numOfItems;
        for (int i = 1; i < size; ++i)
            ((ConstInfo)v.elementAt(i)).renameClass(this, oldName, newName);
    } 
                            #location 5 
                            #vulnerability type NULL_DEREFERENCE
#fixed code
                                public void renameClass(String oldName, String newName) {
        LongVector v = items;
        int size = numOfItems;
        classes = new HashMap(classes.size() * 2);
        for (int i = 1; i < size; ++i) {
            ConstInfo ci = (ConstInfo)v.elementAt(i);
            ci.renameClass(this, oldName, newName);
            ci.makeHashtable(this);
        }
    }