can you be more specific about the problem. I am not sure which existing class you are looking for? you can create table in the database at run time and also check for the existing table in the database.
You can try by giving this condition "Select table_name from all_tables where table_name='YOUR TABLE NAME' ". If the output of this is null then, it is not existing. If it returns some value, then it exists.
Remember, you can access all_tables table only if you hv permission else you can use user_objects instead of all_tables. You have to specify the tablename that you want to search in CAPS only
