Closing of parent class and subclass windows in jframe

I made a student management Applet and needed to call the display subclass window in the parent class window. However, when the subclass window is closed, the parent class window is also closed, then I checked it to solve the problem:

1. I used frame. setdefadefacloseoperation (jframe. exit_on_close) to close it, and exit indicates that the Java application is exited. So I changed it to frame. setdefadefacloseoperation (jframe. dispose_on_close.

2. If the event listening response is used, use dispose () instead of system. Exit (0 );

I used the first method. After the change, I can close it normally. I hope it will help my friends who encounter the same problem.