Generating random sprites

General Discussions
#1 
package minigames;

import java.awt.Color;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.RenderingHints;

import javax.swing.JFrame;
import javax.swing.JPanel;

public class fallingball extends JPanel {
	
	
	int x = 250;
	int y = 0;
	
	private void moveBall() {
		y = y + 1;
		
		
	}
	

	public void paint(Graphics g){
		super.paint(g);
		Graphics2D g2d = (Graphics2D) g;
		g2d.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
		g2d.setColor(Color.black);
		g2d.fillOval(x, y, 30, 30);
	}
	
	public static void main(String[] args) throws InterruptedException{
		JFrame f = new JFrame("Falling Ball");
		fallingball game = new fallingball();
		f.add(game);
		f.setSize(500, 500);
		f.setResizable(false);
		f.setLocationRelativeTo(null);
		f.setVisible(true);
		f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
		
		while (true) {
			game.moveBall();
			game.repaint();
			Thread.sleep(10);
		}
	}

}

only 1 ball is generated and it gets fallen down. i wanted to generate balls falling randomly and from different x co-ordinate in the frame how can i do that