同一帧中的Java图形绘画

Question

我有类画这样的矩形和线条

class MyCanvas extends JComponent {
    int a,b,c,d;
    String control;
    public void setProps(int a, int b,int c,int d,String control) {
        this.a=a; this.b=b; this.c=c; this.d=d; this.control=control;
        repaint();//mark this component to be repainted
    }
    public void paint(Graphics g) {
        super.paint(g);
        if(control.equals("rect")){
        	g.setColor(Color.BLUE);
        	 g.drawRect(a, b, c, d);
        	 
        	 
        }else if(control.equals("line")){
        	g.drawLine(a, b, c, d);
        }
       
    }
}

public class drawShape {
	
  public drawShape(int aa,int bb,int cc,int dd,String oo){
    JFrame window = new JFrame();
    window.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
    window.setBounds(30, 30, 500, 500);
    MyCanvas canvas=new MyCanvas();
    canvas.setProps(aa,bb,cc,dd,oo);
    window.getContentPane().add(canvas);
    window.setVisible(true);
  }
}

我是我的另一课，我打电话

drawShape d1 = new drawShape(keepvar1,keepvar2,keepvar3,keepvar4,"line");

它创建新帧每次调用我想在同一帧中创建rectagle或行

我应该怎么做