Help with JButton

import java.awt.BorderLayout;
import java.awt.Container;
import java.awt.FlowLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.sql.*;
import javax.swing.*;

public class FlightManager implements ActionListener{
    
    // JDBC driver name and database url
    static final String DRIVER = "com.mysql.jdbc.Driver";
    static final String DATABASE_URL = "jdbc:mysql://localhost:3306/flightmanager";
    private JTextField fn = new JTextField(15);
    private JTextField oc  = new JTextField(15);
    private JTextField dc = new JTextField(15);
    private JTextField dt = new JTextField(15);
    private JLabel fnl = new JLabel("Flight Number: ");
    private JLabel ocl = new JLabel("City of Origin: ");
    private JLabel dcl = new JLabel("Destination City: ");
    private JLabel dtl = new JLabel("Departure Time: ");
    private int flightNum;
    private String originCity;
    private String destinationCity;
    private String departure;
    private JButton addButton;
    private JButton removeButton;
    private JButton searchButton;
    private JButton exitButton;
        
    public static void main(String[] args) throws SQLException {

        Connection connection = null;
        Statement statement = null;
        ResultSet resultSet = null;
        try {
        
            Class.forName(DRIVER);
            connection = DriverManager.getConnection(DATABASE_URL, "root", "lilly");
        } catch (ClassNotFoundException ex) {
            ex.printStackTrace();
        }

        FlightManager fm = new FlightManager();
        Container pc = new Container();
        pc.setLayout(new BoxLayout(pc, BoxLayout.Y_AXIS));
        JPanel blank = new JPanel();
        pc.add(blank);
        pc.add(fm.getFlightInputPanel());
        pc.add(fm.getOriginPanel());
        pc.add(fm.getDestinationPanel());
        pc.add(fm.getDepartureTimePanel());
        
        JFrame f = new JFrame();
        f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        f.add(pc, "First");
        f.add(fm.getButtonPanel(), "Last"); // adds button panel to JFrame
        f.setSize(500, 200);
        f.setLocation(200,200);
        f.setVisible(true);
        
        
        
    }
    
    private JPanel getFlightInputPanel(){
        FlowLayout flightInputLayout = new FlowLayout(FlowLayout.CENTER);
        JPanel fnp = new JPanel();
        fnp.add(fnl);
        fnp.add(fn);
        
        return fnp;
    }
    
    private JPanel getOriginPanel(){
        FlowLayout flightInputLayout = new FlowLayout(FlowLayout.CENTER);
        JPanel ocp = new JPanel();
        ocp.add(ocl);
        ocp.add(oc);
        
        return ocp;
    }
    
    private JPanel getDestinationPanel(){
        FlowLayout flightInputLayout = new FlowLayout(FlowLayout.CENTER);
        JPanel dcp = new JPanel();
        dcp.add(dcl);
        dcp.add(dc);
        
        return dcp;
    }
    
    private JPanel getDepartureTimePanel(){
        FlowLayout flightInputLayout = new FlowLayout(FlowLayout.CENTER);
        JPanel dtp = new JPanel();
        dtp.add(dtl);
        dtp.add(dt);
        
        return dtp;
    }
    
    private JPanel getButtonPanel(){
        
        FlowLayout buttonLayout = new FlowLayout(FlowLayout.CENTER);
        JPanel buttonPanel = new JPanel();
        addButton = new JButton("Add Flight");
        addButton.addActionListener(this);
        removeButton = new JButton("Delete Flight");
        removeButton.addActionListener(this);
        searchButton = new JButton("Search For Flight");
        searchButton.addActionListener(this);
        exitButton = new JButton("Exit");
        exitButton.addActionListener(this);
        buttonPanel.add(addButton);
        buttonPanel.add(removeButton);
        buttonPanel.add(searchButton);
        buttonPanel.add(exitButton);
     
        return buttonPanel;
    }
    
    
    // processes actions for when buttons are pushed
    public void actionPerformed(ActionEvent e) {

        // action to take if add ball button is pushed
        if(e.getSource() == addButton)
            
            flightNum = Integer.parseInt(fn.getText());
            originCity = oc.getText();
            destinationCity = dc.getText();
            departure = dt.getText();
            
            // clears out current contents of JTextFields
            fn = null;
            oc = null;
            dc = null;
            dt = null;
        
        // action to take if delete ball button is pushed
        if(e.getSource() == searchButton)

        if(e.getSource() == removeButton)
        
            
        // action to take if exit button is pushed
        if(e.getSource() == exitButton)
            System.exit(0);
    }
   }