graphics - simply print a component in java with a diagonal line -

i'm beginner trying print basic window line 0,0,500,500. i've tried validate, dolayout, printall. unsure g in printall. can't find anywhere says is. ??

package helloprogram;     import java.awt.graphics.*;  /**  *  * @author jglvn  */  class component{  void setsize(int width, int height){     }  void setbounds(int x, int y){       }  void drawline(int x1, int y1, int x2, int y2){       }  void setbackground(int r, int g, int b){       }  void validate(){       }  void dolayout(){       }  void printall(graphics g){     }  }   public class helloprogram {  public static void main(string[] args) {      component canvas = new component();     canvas.setsize(500, 500);     canvas.setbounds(300, 300);     canvas.setbackground(153,153,153);     canvas.drawline(0, 0, 500, 500);     canvas.dolayout();     canvas.validate();     canvas.printall(g);     }  } 

it seams want draw line in frame. if case, should go container jpanel. want paint on panel, should override paint method:

here sample code:

import java.awt.graphics; import java.awt.graphics2d; import java.awt.point; import javax.swing.jframe; import javax.swing.jpanel;  public class drawlinepanel extends jpanel{ private static final int frame_height = 600; private static final int frame_width = 600;  public static void main(string[] args) {     jframe f = new jframe();     f.setdefaultcloseoperation(jframe.exit_on_close);     f.setsize(frame_width, frame_height);     f.add(new drawlinepanel(new point(100, 100), new point(500, 500)));     f.setvisible(true); }  private point pointa; private point pointb;  public drawlinepanel(point pointa, point pointb) {     this.pointa = pointa;     this.pointb = pointb; }  @override public void paint(graphics g) {     super.paintcomponents(g);     //      graphics2d g2 = (graphics2d) g;     g2.drawline(pointa.x, pointa.y, pointb.x, pointb.y); } } 

some advice:

1. don't make frame visible before graphics.

2. don't mix component sub classes frame or panel jcomponent sub classes jframe or jpanel.

hope helpful.