Java tutorial
import java.awt.Frame; public class Main { public static void main(String[] argv) throws Exception { Frame frame = new Frame(); frame.setSize(300, 300); frame.setVisible(true); maximize(frame); } public static void maximize(Frame frame) { int state = frame.getExtendedState(); // Set the maximized bits state |= Frame.MAXIMIZED_BOTH; // Maximize the frame frame.setExtendedState(state); } }