passing a value from a jframe and use it to another

I have a problem regarding on how to pass value from one JFrame to another and use it to an sql query.

Let's be more clear. I want to make a programm which has to JFrames. the first is a login frame. I want to take the value which the user has entered in the username textfield and use it to load a table which is unique for the each user.

More simply i want to replace the userName in this query

String sql ="select league from Teams where team_owner= '"+userName+"' ";