Drawing simple curve in java

if (pen_type==1){
           g2.fillOval( x, y, stroke_width, stroke_width );
       }  else if (pen_type==2) {
           g2.draw(new Line2D.Double(x, y, stroke_width, stroke_width));
       }
       else {
            //x1= ((76-4)/(6-0));
           // y= ((76-4)/(30-29));
           //y=((x*x*x)-(3*x));
           g2.setStroke(new BasicStroke(stroke_width, BasicStroke.CAP_ROUND,BasicStroke.JOIN_ROUND));
           g2.drawLine(last_x, last_y,x,y);
            //g2.drawArc ( 0, 0, getWidth (), getHeight (), 80, -245 );
           //g2.draw(new Line2D.Double(x, y, stroke_width, stroke_width));

            //g2.drawArc(last_x, last_y, getWidth (), getHeight (), 90, 60);

           //g2.drawArc(x1, y1, last_x, last_y,5,5);

             QuadCurve2D.Double curve = new QuadCurve2D.Double(last_x, last_y,x1,y1,x,y);
             g2.draw(curve);



           //CubicCurve2D c = new CubicCurve2D .Float();
           //c.setCurve(x1, y1, last_x, last_y, x, y,x1,y1);
          // g2.draw(c);

       };