How to set inner window size for JFrame?

Question

Java

I call the setBounds(0, 0, 100, 100) method, but the window size is clearly not 100 in height. apparently in 100px the size of the title with the cross of the window closing is laid. now the purpose - to set the internal size of a window.
pack() reduces the size of the entire window to somewhere around 2x30px even after adding a 100x100 JInternalFrame element to the main JFrame.
I can't think of a better way to write. Is it possible to fit the outer Jframe to the size of the nested JInternalFrame, or how is it done in such cases?