import javax.swing.JOptionPane;
/**
 * @web http://www.jc-mouse.net/
 * @author Mouse
 */
public class jFrameBlocked extends javax.swing.JFrame {

    /**
     * Creates new form jFrameBlocked
     */
    public jFrameBlocked() {
        
        this.setUndecorated(true);//quita bordes a jframe
        
        initComponents();
        
        this.setDefaultCloseOperation( DO_NOTHING_ON_CLOSE  );//evita cerra jframe con ALT+C
        this.setExtendedState( MAXIMIZED_BOTH );//maximizado
        this.setAlwaysOnTop(true);//siempre al frente       
        //nueva instancia de jBlocked pasando como parametros e este JFrame
        new jBlocked( this ).block();
        
    }

    /**
     * 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">//GEN-BEGIN:initComponents
    private void initComponents() {
        java.awt.GridBagConstraints gridBagConstraints;

        jPanel1 = new javax.swing.JPanel();
        jPanel2 = new javax.swing.JPanel();
        jLabel1 = new javax.swing.JLabel();
        jLabel2 = new javax.swing.JLabel();
        user = new javax.swing.JTextField();
        pass = new javax.swing.JTextField();
        btnSalir = new javax.swing.JButton();
        btnEntrar = new javax.swing.JButton();

        setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);

        jPanel1.setBackground(new java.awt.Color(51, 51, 255));
        jPanel1.setBorder(javax.swing.BorderFactory.createEmptyBorder(1, 1, 1, 1));
        jPanel1.setLayout(new java.awt.GridBagLayout());

        jPanel2.setBorder(javax.swing.BorderFactory.createEtchedBorder());
        jPanel2.setLayout(new java.awt.GridBagLayout());

        jLabel1.setText("Usuario :");
        gridBagConstraints = new java.awt.GridBagConstraints();
        gridBagConstraints.gridx = 0;
        gridBagConstraints.gridy = 0;
        gridBagConstraints.anchor = java.awt.GridBagConstraints.WEST;
        gridBagConstraints.insets = new java.awt.Insets(40, 40, 5, 5);
        jPanel2.add(jLabel1, gridBagConstraints);

        jLabel2.setText("Contraseña :");
        gridBagConstraints = new java.awt.GridBagConstraints();
        gridBagConstraints.gridx = 0;
        gridBagConstraints.gridy = 1;
        gridBagConstraints.anchor = java.awt.GridBagConstraints.WEST;
        gridBagConstraints.insets = new java.awt.Insets(5, 40, 5, 5);
        jPanel2.add(jLabel2, gridBagConstraints);

        user.setPreferredSize(new java.awt.Dimension(200, 32));
        gridBagConstraints = new java.awt.GridBagConstraints();
        gridBagConstraints.gridx = 1;
        gridBagConstraints.gridy = 0;
        gridBagConstraints.gridwidth = 2;
        gridBagConstraints.anchor = java.awt.GridBagConstraints.NORTHWEST;
        gridBagConstraints.insets = new java.awt.Insets(40, 5, 5, 40);
        jPanel2.add(user, gridBagConstraints);

        pass.setPreferredSize(new java.awt.Dimension(200, 32));
        gridBagConstraints = new java.awt.GridBagConstraints();
        gridBagConstraints.gridx = 1;
        gridBagConstraints.gridy = 1;
        gridBagConstraints.gridwidth = 2;
        gridBagConstraints.anchor = java.awt.GridBagConstraints.NORTHWEST;
        gridBagConstraints.insets = new java.awt.Insets(5, 5, 5, 40);
        jPanel2.add(pass, gridBagConstraints);

        btnSalir.setText("Cancelar");
        btnSalir.addActionListener(new java.awt.event.ActionListener() {
            public void actionPerformed(java.awt.event.ActionEvent evt) {
                btnSalirActionPerformed(evt);
            }
        });
        gridBagConstraints = new java.awt.GridBagConstraints();
        gridBagConstraints.gridx = 2;
        gridBagConstraints.gridy = 2;
        gridBagConstraints.anchor = java.awt.GridBagConstraints.NORTHWEST;
        gridBagConstraints.insets = new java.awt.Insets(30, 10, 40, 0);
        jPanel2.add(btnSalir, gridBagConstraints);

        btnEntrar.setText("Entrar");
        btnEntrar.addActionListener(new java.awt.event.ActionListener() {
            public void actionPerformed(java.awt.event.ActionEvent evt) {
                btnEntrarActionPerformed(evt);
            }
        });
        gridBagConstraints = new java.awt.GridBagConstraints();
        gridBagConstraints.gridx = 1;
        gridBagConstraints.gridy = 2;
        gridBagConstraints.anchor = java.awt.GridBagConstraints.NORTHWEST;
        gridBagConstraints.insets = new java.awt.Insets(30, 0, 40, 0);
        jPanel2.add(btnEntrar, gridBagConstraints);

        gridBagConstraints = new java.awt.GridBagConstraints();
        gridBagConstraints.gridx = 0;
        gridBagConstraints.gridy = 0;
        jPanel1.add(jPanel2, gridBagConstraints);

        getContentPane().add(jPanel1, java.awt.BorderLayout.CENTER);

        pack();
    }// </editor-fold>//GEN-END:initComponents

    private void btnSalirActionPerformed(java.awt.event.ActionEvent evt) {//GEN-FIRST:event_btnSalirActionPerformed
       System.exit(0);
    }//GEN-LAST:event_btnSalirActionPerformed

    private void btnEntrarActionPerformed(java.awt.event.ActionEvent evt) {//GEN-FIRST:event_btnEntrarActionPerformed
        if( this.user.getText().equals("user") && this.pass.getText().equals("1234") )
        {
            new jFrameGUI().setVisible(true);
            this.dispose();            
        }
        else
        {
            JOptionPane.showMessageDialog( this, "Access denied");
        }
    }//GEN-LAST:event_btnEntrarActionPerformed

    /**
     * @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(jFrameBlocked.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        } catch (InstantiationException ex) {
            java.util.logging.Logger.getLogger(jFrameBlocked.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        } catch (IllegalAccessException ex) {
            java.util.logging.Logger.getLogger(jFrameBlocked.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        } catch (javax.swing.UnsupportedLookAndFeelException ex) {
            java.util.logging.Logger.getLogger(jFrameBlocked.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        }
        //</editor-fold>

        /* Create and display the form */
        java.awt.EventQueue.invokeLater(new Runnable() {
            public void run() {
                new jFrameBlocked().setVisible(true);
            }
        });
    }
    // Variables declaration - do not modify//GEN-BEGIN:variables
    private javax.swing.JButton btnEntrar;
    private javax.swing.JButton btnSalir;
    private javax.swing.JLabel jLabel1;
    private javax.swing.JLabel jLabel2;
    private javax.swing.JPanel jPanel1;
    private javax.swing.JPanel jPanel2;
    private javax.swing.JTextField pass;
    private javax.swing.JTextField user;
    // End of variables declaration//GEN-END:variables
}

import java.util.concurrent.Executors;
import java.util.concurrent.ScheduledExecutorService;
import java.util.concurrent.TimeUnit;
import javax.swing.JFrame;
/**
 * @web http://www.jc-mouse.net/
 * @author Mouse
 */
public class jBlocked {
    
    private JFrame jframe=null;
    
    /**
     * Constructor de clase
     */
    public jBlocked( JFrame f )
    {
        this.jframe = f;
    }
    
    /**
     * ejecuta una tarea cada "n" tiempo
     * Para evitar que el usuario utilice las teclas (WINDOWS + D)(TAB) y asi perder el foco
     * de la aplicación, cada 50 milisegundos se envia el JFrame al frente y se cambia su propiedad a maximizado
     */
    public void block()
    {
        ScheduledExecutorService scheduler = Executors.newSingleThreadScheduledExecutor();
        scheduler.scheduleAtFixedRate( 
            new Runnable() 
            {
                @Override
                public void run() {                   
                    front(); 
                }
              }, 500, 50 , TimeUnit.MILLISECONDS ); //comienza dentro de 1/2 segundo y luego se repite cada N segundos
    }
    
    /**
     * 
     */
    public void front()
    {
        jframe.setExtendedState( JFrame.MAXIMIZED_BOTH );//maximizado
        jframe.toFront();
    }
    
}//--> fin

public class jFrameGUI extends javax.swing.JFrame {

    /**
     * Creates new form jFrameGUI
     */
    public jFrameGUI() {
        initComponents();
        this.setLocationRelativeTo(null);//posicion al centro de la pantalla            
        this.setAlwaysOnTop(true);//siempre al frente        
    }

    /**
     * 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">//GEN-BEGIN:initComponents
    private void initComponents() {
        java.awt.GridBagConstraints gridBagConstraints;

        jLabel1 = new javax.swing.JLabel();
        jLabel2 = new javax.swing.JLabel();

        setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);
        setTitle("Access granted");
        getContentPane().setLayout(new java.awt.GridBagLayout());

        jLabel1.setFont(new java.awt.Font("Tahoma", 1, 36)); // NOI18N
        jLabel1.setHorizontalAlignment(javax.swing.SwingConstants.CENTER);
        jLabel1.setText("Congratulations");
        gridBagConstraints = new java.awt.GridBagConstraints();
        gridBagConstraints.gridx = 0;
        gridBagConstraints.gridy = 0;
        gridBagConstraints.insets = new java.awt.Insets(40, 100, 10, 100);
        getContentPane().add(jLabel1, gridBagConstraints);

        jLabel2.setFont(new java.awt.Font("Tahoma", 1, 24)); // NOI18N
        jLabel2.setHorizontalAlignment(javax.swing.SwingConstants.CENTER);
        jLabel2.setText("Access granted");
        gridBagConstraints = new java.awt.GridBagConstraints();
        gridBagConstraints.gridx = 0;
        gridBagConstraints.gridy = 1;
        gridBagConstraints.insets = new java.awt.Insets(10, 10, 50, 10);
        getContentPane().add(jLabel2, gridBagConstraints);

        pack();
    }// </editor-fold>//GEN-END:initComponents

    /**
     * @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(jFrameGUI.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        } catch (InstantiationException ex) {
            java.util.logging.Logger.getLogger(jFrameGUI.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        } catch (IllegalAccessException ex) {
            java.util.logging.Logger.getLogger(jFrameGUI.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        } catch (javax.swing.UnsupportedLookAndFeelException ex) {
            java.util.logging.Logger.getLogger(jFrameGUI.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        }
        //</editor-fold>

        /* Create and display the form */
        java.awt.EventQueue.invokeLater(new Runnable() {
            public void run() {
                new jFrameGUI().setVisible(true);
            }
        });
    }
    // Variables declaration - do not modify//GEN-BEGIN:variables
    private javax.swing.JLabel jLabel1;
    private javax.swing.JLabel jLabel2;
    // End of variables declaration//GEN-END:variables
}