Recently I was asked "How can I maximize a frame (JFrame) in Java?" Once you know how to do it, it turns out to be pretty easy. Here's some code that shows how to maximize a JFrame:

MyJFrame myFrame = new MyJFrame();

// do your own stuff here ...

// do the maximization here
myFrame.setExtendedState(myFrame.getExtendedState()|JFrame.MAXIMIZED_BOTH);

// do whatever else you want to do ...
myFrame.setVisible();