JFrame.setDefaultLookAndFeelDecorated(true);

Question

when i use setDefaultLookAndFeelDecorated(true) method in Java why is the Frame appear FullScreen when i maximize the Frame ? and how can i disaple the FullScreen mode in this method ?

Answer 1

Setting setDefaultLookAndFeelDecorated to true causes the decorations to be handled by the look and feel; this means that a System look-and-feel on both Windows and Mac (I have no Linux at hand now) retains the borders you would expect them of a native window, e.g. staying clear of the taskbar in Windows.

When using the Cross Platform look-and-feel, a.k.a. Metal, which is the default on Windows, the Windows version will take over the entire screen, making it look like a full-screen window. On Mac, the OS refuses to give away its own titlebar, and draws a complete Metal frame (including the title bar) in a Mac-native window.

So, in short, if you want to make sure the taskbar gets respected, use the Windows system look-and-feel on Windows. You can set it by using something like

UIManager.setLookAndFeel((LookAndFeel) Class.forName(UIManager.getCrossPlatformLookAndFeelClassName()).newInstance());

Answer 2

If you don't want your JFrame to be maximize-able then then call .setResizable(false); on it.