Unable to drop table via Jackcess using getSystemTable and findFirstRow

Why can't cursor findFirstRow when I try to use Jackcess to find the row that I need to delete in order to drop a table?

private static void deleteTable(Database db, String tableName) throws IOException {
    Table table = db.getSystemTable(tableName);
    if (table == null) {
        return;
    }
    Cursor cursor = table.getDefaultCursor();
    Map<String, Object> criteria = new HashMap<String, Object>();
    criteria.put("Name", tableName);
    criteria.put("Type", (short) 1);
    if (cursor.findFirstRow(criteria)) {
        table.deleteRow(cursor.getCurrentRow());
        Log.e(TAG, "delete " + tableName + "   success!");
    } else {
        Log.e(TAG, "can't find this Table");//run here
    }
    db.flush();
    db.close();
}

PS.: no reported exception

Your mistake is that you are opening the table you want to delete, not the system table that holds the list of database objects. Instead of

Table table = db.getSystemTable(tableName);

you need to use

Table table = db.getSystemTable("MSysObjects");