public enum UtilidadesVentana {

INSTANCE;

public static GraphicsConfiguration getDefaultGraphicsConfig() {
return getLocalGraphicsEnvironment().getDefaultScreenDevice().getDefaultConfiguration();
}

public static Rectangle getUsableScreenBounds(final GraphicsConfiguration gc) {
final Insets insets = getDefaultToolkit().getScreenInsets(gc);
final Rectangle bounds = gc.getBounds();
bounds.x += insets.left;
bounds.y += insets.top;
bounds.width -= insets.left + insets.right;
bounds.height -= insets.top + insets.bottom;
return bounds;
}

public static Rectangle getUsableScreenBounds() {
return getUsableScreenBounds(getDefaultGraphicsConfig());
}

public static Point getPointForCentering(final Window window) {
final Rectangle usableBounds = getUsableScreenBounds();
return new Point((usableBounds.width - window.getWidth()) / 2, (usableBounds.height - window.getHeight()) / 2);
}

}

public class NewJFrame extends javax.swing.JFrame {

private static final long serialVersionUID = 2_711_955_152_747_636_374L;

/** Creates new form NewJFrame */
public NewJFrame() {
initComponents();
}

/** This method is called from within the constructor to
initialize the form.
WARNING: Do NOT modify this code. The content of this method is
always regenerated by the Form Editor.
*/
@SuppressWarnings("unchecked")
// <editor-fold defaultstate="collapsed" desc="Generated Code">
private void initComponents() {

setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);
setTitle("Ventana centrada");

javax.swing.GroupLayout layout = new javax.swing.GroupLayout(getContentPane());
getContentPane().setLayout(layout);
layout.setHorizontalGroup(
layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addGap(0, 400, Short.MAX_VALUE)
);
layout.setVerticalGroup(
layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addGap(0, 300, Short.MAX_VALUE)
);

pack();
}// </editor-fold>

/**
@param args the command line arguments
*/
public static void main(String args[]) {
/* Set the Nimbus look and feel */
//<editor-fold defaultstate="collapsed" desc=" Look and feel setting code (optional) ">
/* If Nimbus (introduced in Java SE 6) is not available, stay with the default look and feel.
* For details see http://download.oracle.com/javase/tutorial/uiswing/lookandfeel/plaf.html
*/
try {
for (javax.swing.UIManager.LookAndFeelInfo info : javax.swing.UIManager.getInstalledLookAndFeels()) {
if ("Nimbus".equals(info.getName())) {
javax.swing.UIManager.setLookAndFeel(info.getClassName());
break;
}
}
} catch (ClassNotFoundException ex) {
java.util.logging.Logger.getLogger(NewJFrame.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
} catch (InstantiationException ex) {
java.util.logging.Logger.getLogger(NewJFrame.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
} catch (IllegalAccessException ex) {
java.util.logging.Logger.getLogger(NewJFrame.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
} catch (javax.swing.UnsupportedLookAndFeelException ex) {
java.util.logging.Logger.getLogger(NewJFrame.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
}
//</editor-fold>

/* Create and display the form */
java.awt.EventQueue.invokeLater(new Runnable() {
@Override
public void run() {
NewJFrame newJFrame = new NewJFrame();
newJFrame.setLocation(UtilidadesVentana.getPointForCentering(newJFrame));
newJFrame.setVisible(true);
}
});
}

// Variables declaration - do not modify
// End of variables declaration
}