MainMenuGUI.java

import java.awt.Color;
import java.awt.Dimension;
import java.awt.FlowLayout;
import java.awt.Graphics;
import java.awt.GridLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.util.Random;

import javax.swing.BorderFactory;
import javax.swing.JButton;
import javax.swing.JComboBox;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.border.Border;

public class MainMenuGUI extends JFrame implements ActionListener {

    private JLabel l1 = new JLabel("Are you sure you want to Exit?");

    private JButton addCustomer;
    private JButton addEmployee;
    private JButton updateCustomer;
    private JButton updateEmployee;
    private JButton viewEmployeeDetails;
    private JButton viewCustomerDetails;
    private JButton exit;

    MainMenuGUI() {
        setTitle("Customer and Employee Details");

        setSize(650, 650);
        // Set Layout 3 Rows and 1 Column
        setLayout(new GridLayout(3, 1));

        JPanel customerPanel = new JPanel(new FlowLayout());
        JPanel employeePanel = new JPanel(new FlowLayout());
        JPanel bottomPanel = new JPanel(new FlowLayout(FlowLayout.CENTER));

        // Set up Borders
        int eb = 30;

        Border customerBorder = BorderFactory.createCompoundBorder(
                BorderFactory.createEmptyBorder(eb, eb, eb, eb),
                BorderFactory.createTitledBorder("Customer"));
        Border employeeBorder = BorderFactory.createCompoundBorder(
                BorderFactory.createEmptyBorder(eb, eb, eb, eb),
                BorderFactory.createTitledBorder("Employee"));
        Border systemBorder = BorderFactory.createCompoundBorder(
                BorderFactory.createEmptyBorder(eb, eb, eb, eb),
                BorderFactory.createTitledBorder("System"));

        customerPanel.setBorder(customerBorder);
        employeePanel.setBorder(employeeBorder);

        bottomPanel.setBorder(systemBorder);

        // Initialise Buttons
        addCustomer = new JButton("Add Customer");
        addEmployee = new JButton("Add Employee");
        updateCustomer = new JButton("Update Customer");
        updateEmployee = new JButton("Update Employee");
        viewCustomerDetails = new JButton("View Customer Details");
        viewEmployeeDetails = new JButton("View Employee Details");
        exit = new JButton("Exit");

        // Set Button Sizes
        addCustomer.setPreferredSize(new Dimension(180, 30));
        addEmployee.setPreferredSize(new Dimension(180, 30));
        updateCustomer.setPreferredSize(new Dimension(180, 30));
        updateEmployee.setPreferredSize(new Dimension(180, 30));
        viewCustomerDetails.setPreferredSize(new Dimension(180, 30));
        viewEmployeeDetails.setPreferredSize(new Dimension(180, 30));
        exit.setPreferredSize(new Dimension(180, 30));


        // Add buttons to Customer Panel
        customerPanel.add(addCustomer);
        customerPanel.add(updateCustomer);
        customerPanel.add(viewCustomerDetails);

        // Add buttons to Employee Panel
        employeePanel.add(addEmployee);
        employeePanel.add(updateEmployee);
        employeePanel.add(viewEmployeeDetails);

        // Add buttons to System Panel
        bottomPanel.add(exit);

        // Add Panels to JFrame
        add(customerPanel);
        add(employeePanel);
        add(bottomPanel);

        // Add action listener to buttons
        addCustomer.addActionListener(this);
        addEmployee.addActionListener(this);;
        updateCustomer.addActionListener(this);;
        updateEmployee.addActionListener(this);;
        viewEmployeeDetails.addActionListener(this);;
        viewCustomerDetails.addActionListener(this);;
        exit.addActionListener(this);;

        setDefaultCloseOperation(EXIT_ON_CLOSE);
        setVisible(true);

    }

    @Override
    public void actionPerformed(ActionEvent e) {

        if(e.getActionCommand().equalsIgnoreCase("Add Customer"))
        {
            AddCustomerGUI cust = new AddCustomerGUI();
            this.dispose();

        }
        if(e.getActionCommand().equalsIgnoreCase("Add Employee"))
        {
            AddEmployeeGUI cust = new AddEmployeeGUI();
            this.dispose();

        }

    }
}