// For fullscreen, put the following in your code:
frame.setExtendedState(JFrame.MAXIMIZED_BOTH);
// You can also set the dimensions of the window like this:
frame.setSize(1920, 1080); // Change to resolution of your screen.
// Set fullscreen mode in libgdx.
DisplayMode display = Lwjgl3ApplicationConfiguration.getDisplayMode();
config.setFullscreenMode(display);