My question is why when I press to the restore down (on a Windows platform) the JFrame is very tiny (see the bellow screenshot).
I use this code regarding State of the JFrame:
this.setExtendedState(View.MAXIMIZED_BOTH);
I need to use setMinimumSize()?

Be sure that
this.setExtendedState(JFrame.MAXIMIZED_BOTH)is executed AFTERsetVisible(true). Also if you have asetResizable(false)call make sure it is executed AFTER thesetExtendedState()one.