Capturar las dimensiones del monitor

dimensiones-monitor.java

import javax.swing.JFrame;
import java.awt.Dimension;
import java.awt.Toolkit;

final JFrame frame = new JFrame();

Dimension fullscreen = Toolkit.getDefaultToolkit().getScreenSize();
fullscreen.width -= 100;
fullscreen.height -= 200;
frame.setBounds(0,0,fullscreen.width,fullscreen.height);