Trying to make a simple game but thr result is blank grey screen

import java.awt.Dimension;
import java.awt.GridLayout;

import javax.swing.*;


public class Frame extends JFrame{

	public static String title = "Tower Defence	                                                                  ";
	public static Dimension size = new Dimension(700,550);
	
	public Frame(){//main frame
		setTitle(title);	
		setSize(size);
		setResizable(false);
		setBackground(null);
		setLocationRelativeTo(null);
		setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
		
		init();
	}
	
	public void init(){
		setLayout(new GridLayout(1, 1, 0, 0));//set a window inside our main frame
		
		Screen screen = new Screen();	
	        add(screen);  //******update*******
		setVisible(true);
	}

	public static void main(String[] args){
		Frame frame = new Frame();
	}

}

import java.awt.Color;
import java.awt.Graphics;

import javax.swing.*;

public class Screen extends JPanel implements Runnable {

	public Thread t1 = new Thread(this);
	public static boolean isFirst = true;
	public static int myWitdh,myHeight;
	public static Room room;
	
	
	public Screen(){
		t1.start();
	}
	
	public void paintComponenr(Graphics g){
		if(isFirst){
			define();
			
			isFirst = false;
		}
		
		g.clearRect(0, 0, getWidth(), getHeight());
		
		room.draw(g);//drawing the room
	}
	
	private void define() {
		room = new Room();
	}

	public void run(){
		while(true){
			if(!isFirst){
				room.physic();
			}
			
			repaint();
			
			try {
				Thread.sleep(1);
			} catch (InterruptedException e) {}
			
		}
	}
}

import java.awt.Graphics;


public class Room {
	
	public int worldWidth = 10;
	public int worldheight = 6;
	public int blockSize = 32;
	public Block[][]block;
	
	
	public Room(){
		define();
	}
	
	private void define() {
		block = new Block[worldWidth][worldheight];
		
		for( int y=0 ; y<block.length ; y++ ){
			for( int x=0 ; x<block[0].length ; x++ ){
				block[y][x] = new Block( x*blockSize, y*blockSize, blockSize, blockSize, 0, 0);
			}
			
		}
	}

	public void physic(){
		
	}
	
	public void draw(Graphics g){
		for( int y=0 ; y<block.length ; y++ ){
			for( int x=0 ; x<block[0].length ; x++ ){
				block[y][x].draw(g);
			}
			
		}
	}
}

import java.awt.Graphics;
import java.awt.Rectangle;


public class Block extends Rectangle {
	public int groundID;
	public int airID;
	
	public Block(int x, int y, int w, int h,int ground ,int air){
		setBounds(x,y,w,h);
		this.groundID = ground;
		this.airID = air;
	}
	
	public void draw(Graphics g){
		g.drawRect(x, y, width,height );
	}
}