19. FlowLayout - Set Alignment through buttons and a container

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;

public class Gui extends JFrame{

    // Variables
    private JButton lb;
    private JButton cb;
    private JButton rb;
    private FlowLayout layout;
    private Container container;

    // Constructor
    public Gui(){

        // Basics
        super("JFrame's title");
        layout = new FlowLayout();
        setLayout(layout);
        container = getContentPane();

        // Buttons
        lb = new JButton("Left");
        add(lb);
        lb.addActionListener(
                new ActionListener() {
                    @Override
                    public void actionPerformed(ActionEvent event) {
                        layout.setAlignment(FlowLayout.LEFT);
                        layout.layoutContainer(container);
                    }
                }
        );
        cb = new JButton("Center");
        add(cb);
        cb.addActionListener(
                new ActionListener() {
                    @Override
                    public void actionPerformed(ActionEvent event) {
                        layout.setAlignment(FlowLayout.CENTER);
                        layout.layoutContainer(container);
                    }
                }
        );
        rb = new JButton("Right");
        add(rb);
        rb.addActionListener(
                new ActionListener() {
                    @Override
                    public void actionPerformed(ActionEvent event) {
                        layout.setAlignment(FlowLayout.RIGHT);
                        layout.layoutContainer(container);
                    }
                }
        );

    }

    // Main Function
    public static void main(String[] agrs){
        Gui gui = new Gui();
        gui.setDefaultCloseOperation(EXIT_ON_CLOSE);
        gui.setSize(400, 400);
        gui.setVisible(true);
    }
}