Error when trying to change the color of background and the absolute position of elements in Java GUI

Question

I'm trying to create a JButton (r) and to set its absolute position. I also want to change the background color. When I insert a new FlowLayout like this: setLayout(new FlowLayout()); the color of the background doesn't change while the absolute position does.

Meanwhile when removing this: setLayout(new FlowLayout()); the absolute position doesn't change while the color does. So can anyone explain me why this happens and how can I change the code in a way thet both of them the color and the posiotion absolute of the JButton change?

This is my code:

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

public class Back extends JFrame{

    private JButton r;
    private JButton c;
    private Container container;
    public Back(){
        super("title");
        //setLayout(new FlowLayout());
        ran = new Random();
        value = nextValue();

        r=new JButton("ROLL");
        add(r,BorderLayout.SOUTH);

        thehandler hand=new thehandler(this);//konstruktori i handler merr nje instance te Background
        r.addActionListener(hand);
    }

    private class thehandler implements ActionListener{
        public void actionPerformed(ActionEvent event) {
        }
    }

    public static void main(String[] args) {
         Back  d = new Back() ;

         d.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
         d.getContentPane().setBackground(Color.GREEN);
         d.setSize(700,500);

         d.setVisible(true);    
    }
}

Answer 1

import java.awt.Color;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.util.Random;

import javax.swing.JButton;
import javax.swing.JFrame;

public class Back extends JFrame{

/**
 * 
 */
private static final long serialVersionUID = 1L;
private JButton r;
public Back(){
    super("title");
    setLayout(null);
    r=new JButton("ROLL");
    r.setBounds(20, 20, 70, 30);
    add(r);

    Thehandler hand=new Thehandler(this);//konstruktori i handler merr nje instance te Background
    r.addActionListener(hand);
}

private class Thehandler implements ActionListener{
    private JFrame frame;
    public Thehandler(JFrame frame) {
        this.frame = frame;
    }
    public void actionPerformed(ActionEvent event) {
        Random ra = new Random();
        int r = ra.nextInt(255);
        int g = ra.nextInt(255);
        int b = ra.nextInt(255);
        Color c = new Color(r, g, b);

        frame.getContentPane().setBackground(c);

    }
}

public static void main(String[] args) {
     Back  d = new Back() ;

     d.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
     d.getContentPane().setBackground(Color.GREEN);
     d.setSize(700,500);

     d.setVisible(true);    
}
}