The code to make it impossible to resize your JFrame is:

JFrame frame = new JFrame("Frame Title";
frame.setResizable(false);

I searched for it on google.

Note: The above snipet hides the maximize and minimize buttons of the frame.
I need something that makes them visible but still deactivates the miximize button.

i've discovered that it is on jdk 1.2 that the buttons get hidden. try jdk 1.5. its cool. only the maximize button gets deactivated (not hidden).