import java.awt.GraphicsDevice;
import java.awt.GraphicsEnvironment;
import javax.swing.JFrame;
import javax.swing.JLabel;

public class DualMonitor {
  public static void main(String ... args) {
    GraphicsEnvironment ge = GraphicsEnvironment.getLocalGraphicsEnvironment();
    GraphicsDevice[] gs = ge.getScreenDevices();
    javax.swing.JOptionPane.showConfirmDialog((java.awt.Component)
        null, "Found : " + gs.length, "screen detected ?",
        javax.swing.JOptionPane.DEFAULT_OPTION);
    for (int j = 0; j < gs.length; j++) {
      GraphicsDevice gd = gs[j];
      JFrame  frame = new JFrame(gd.getDefaultConfiguration());
      frame.setTitle("I'm on monitor #" + j);
      frame.setSize(400,200);
      frame.add(new JLabel("hello world"));
      frame.setVisible(true);
    }
  }
}