http://stackoverflow.com/questions/24635801/returning-a-value-from-jbutton

LoginPageUI.java

import java.awt.GridBagConstraints;
import java.awt.GridBagLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

import javafx.beans.property.BooleanProperty;
import javafx.beans.property.SimpleBooleanProperty;

import javax.swing.JButton;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JTextField;

public class LoginPageUI {

    private BooleanProperty isLogin = new SimpleBooleanProperty();

    public LoginPageUI() {

    }

    public JPanel LoginUI() {
        JPanel loginPanel = new JPanel(new GridBagLayout());
        GridBagConstraints c = new GridBagConstraints();
        JLabel usernameLabel = new JLabel("username");
        JLabel passwordLabel = new JLabel("password");
        final JTextField usernameTF = new JTextField(20);
        final JTextField passwordTF = new JTextField(20);
        JButton loginBtn = new JButton("Login");

        c.gridx = 0;
        c.gridy = 1;
        loginPanel.add(usernameLabel, c);

        c.gridx = 1;
        c.gridy = 1;
        loginPanel.add(usernameTF, c);

        c.gridx = 0;
        c.gridy = 2;
        loginPanel.add(passwordLabel, c);

        c.gridx = 1;
        c.gridy = 2;
        loginPanel.add(passwordTF, c);

        c.gridx = 1;
        c.gridy = 3;
        loginPanel.add(loginBtn, c);

        loginBtn.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                String u = usernameTF.getText().toString();
                String p = passwordTF.getText().toString();
                if (u.equals("a") && p.equals("123")) {
                    isLogin.set(true);
                    System.out.println("Inside the system");
                }
            }
        });
        return loginPanel;
    }

    public boolean verifyLogin() {
        return isLogin.get();
    }
    public BooleanProperty loginProperty(){
        return isLogin;
    }

}

Main.java

public class Main {
    public static void main(String[] arg){
        new RunApp();
    }
}

PateTwo.java

import javax.swing.JLabel;
import javax.swing.JPanel;

public class PageTwo {

    public PageTwo() {

    }

    public JPanel displayPageTwo() {
        JLabel label = new JLabel("Welcome to Page Two!");
        JPanel pTwoPanel = new JPanel();
        pTwoPanel.add(label);
        return pTwoPanel;
    }
}

RunApp.java

package JButton;
import java.awt.CardLayout;

import javafx.beans.value.ChangeListener;
import javafx.beans.value.ObservableValue;

import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.SwingUtilities;


public class RunApp {

public RunApp() {
 SwingUtilities.invokeLater(new Runnable() {
        @Override
        public void run() {
            final CardLayout cardLayout = new CardLayout();
            JFrame frame = new JFrame("testing");
            final JPanel panel = new JPanel();
            panel.setLayout(cardLayout);
            final LoginPageUI lPage = new LoginPageUI();
            PageTwo pageTwo = new PageTwo();
            panel.add(lPage.LoginUI(),"1");
            panel.add(pageTwo.displayPageTwo(),"2");

            cardLayout.show(panel, "1");
            lPage.loginProperty().addListener(new ChangeListener<Boolean>(){
                @Override
                public void changed(ObservableValue<? extends Boolean> arg0, Boolean arg1, Boolean arg2) {
                    if(lPage.verifyLogin())
                        cardLayout.show(panel, "2");
                }
            });
            frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
            frame.add(panel);
            frame.pack();
            frame.setLocationRelativeTo(null);
            frame.setVisible(true);
        }
    });
}
}