here is the first topic for me in this forum and won't be the last. I've been recommended with this forum as the more helpful one from java experienced professionals.
I am facing a problem while creating a table with default table model and using the group layout to lay all the components on the frame
all the things are okay for compiling the program as I want but the problem is that all the components included in my table are displayed as strings, I want to know the reason without using other layout manager
Yes, by default, all data is treated as a String. Did you read the JTable API and follow the link on How to Use Tables for an explanation and examples of using a table? The section on Creating a Table Model talks about this issue. Of course you don't need to create a completely new model, you can just extend the DefaultTableModel and override the appropriate method.