6.FlowLayout.java

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

public class Main{
    public static void main(String[] args){

        //Layout Manager = Defines the natural layout for components within a container..
        //FlowLayout = Place components in a row,sized at their prefer size. If the horizontal space in the
        //             container is too small the flowlayout class uses the next available row..

        JFrame frame = new JFrame();
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setSize(500,500);
        frame.setTitle("Hello");
        frame.setLayout(new FlowLayout(FlowLayout.CENTER,10,10));
        
        JPanel panel = new JPanel();
        panel.setPreferredSize(new Dimension(250,250));
        panel.setBackground(Color.darkGray);
        panel.setLayout(new FlowLayout());

        panel.add(new JButton("1"));
        panel.add(new JButton("2"));
        panel.add(new JButton("3"));
        panel.add(new JButton("4"));
        panel.add(new JButton("5"));
        panel.add(new JButton("6"));
        panel.add(new JButton("7"));
        panel.add(new JButton("8"));
        panel.add(new JButton("9"));

        frame.add(panel);
        frame.setVisible(true);
    }
}