i have this code here for creating and drawing array of pixels into an image

import javax.swing.JFrame;
import java.awt.Canvas;
import java.awt.Graphics;
import java.awt.image.BufferStrategy;
import java.awt.image.BufferedImage;
import java.awt.image.DataBufferInt;

public class test extends Canvas implements Runnable{
private static final long serialVersionUID = 1L;
public static int WIDTH = 800;
public static int HEIGHT = 600;
public boolean running=true;
public int[] pixels;
public BufferedImage img;
public static JFrame frame;
private Thread thread;

public static void main(String[] arg) {
    test wind = new test();
    frame = new JFrame("WINDOW");
    frame.add(wind);
    frame.setVisible(true);
    frame.setSize(WIDTH, HEIGHT);
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    wind.init();
}

public void init(){
    thread=new Thread(this);
    thread.start();
    img=new BufferedImage(WIDTH, HEIGHT,BufferedImage.TYPE_INT_RGB);
    pixels=((DataBufferInt)img.getRaster().getDataBuffer()).getData();
    }

public void run(){
    while(running){
        render();
        try {
            thread.sleep(55);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }
}

public void render(){
    BufferStrategy bs=this.getBufferStrategy();
    if(bs==null){
        createBufferStrategy(4);
        return;
    }
    drawRect(0,0,150,150);
    Graphics g= bs.getDrawGraphics();
    g.drawImage(img, 0, 0, WIDTH, HEIGHT, null);
    g.dispose();
    bs.show();

}

private void drawRect(int x, int y, int w, int h) {
    for(int i=x;i<w;i++)
        for(int j=x;j<h;j++)
                pixels[i+j*WIDTH]=346346;


}   }   

Why i get "Component must be a valid peer" error when i remove the line:

frame.add(wind);

Why I want to remove it? Because I want to create a frame using a class object(from another file) and use the code Window myWindow= new Window() to do exactly the same thing

BTW: who knows Java and understands what i wrote please send me a message with your skype or yahoo messenger id.I want to cooperate with you for a project (graphics engine for games)