Thread: getDocumentBase error

note i want to do this code in background class. not in main class.
so i have a main class and a background class.

getting error at

url = getDocumentBase();

also getting error at

getImage
drawImage

background class

import java.awt.Color;
import java.awt.Graphics;
import java.awt.Image;
import java.awt.Rectangle;
import java.net.URL;
 
//#2
public class Background 
{
	/* background image */
	private URL url;
	 private Image background_image1;
	 private double bX1 = 0;
	 private double bDX1 = 0.3;
 
	 private Image background_image2;
	 private double bX2 = 0;
	 private double bDX2 = 1;
 
	 private Main main_class = new Main();
 
	/*** constructor Method ***/
	public Background() 
	{
	}	
 
	public void init() 
	{
		try
		{
			url = getDocumentBase();
		}
		catch(Exception e)
		{
		}
		background_image1 = getImage(url, "image/background/background.png");
		background_image2 = getImage(url, "image/background/background2.png");
	}/*** end of init method ***/
 
 
 
	/*** paint method ***/
	public void paint(Graphics g) 
	{
		g.setColor(new Color(15, 77, 147));  //sky
		g.fillRect(0,0,main_class.getWidth(), main_class.getHeight()); //sky
		g.drawImage(background_image1, (int)bX1, 0, this);//backgroung image
		g.drawImage(background_image1, (int)bX1 + main_class.getWidth(), 0, this);//backgroung image
	}/*** paint method ***/
}