Java – draw a rectangle that will not disappear in the next painting

I tried to create a JPanel that draws a rectangle The team needs to draw many rectangles, but they won't move

class MyPanel extends JPanel{
  private int x,size;
  private Color c;
  public void DrawRect(int x,int y,int size,Color c){
      this.x = x;
      this.y = y;
      this.size = size;
      this.c = c;
      repaint();
  }
  @Override
    public void
    paint(Graphics g) {

        g.setColor(c);
      g.fillRect(x,size,size);
    }

Solution

>Don't overwrite a painting without a very good reason... Use paintcomponent instead

public class MyPanel extends JPanel {

    private List<MyRectangle> lstShapes;
    private Timer populate;

    public MyPanel() {

        lstShapes = new ArrayList<MyRectangle>(25);

        populate = new Timer(40,new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent e) {

                int x = (int) (Math.random() * getWidth());
                int y = (int) (Math.random() * getHeight());
                int width = (int) (Math.random() * (getWidth() / 4));
                int height = (int) (Math.random() * (getHeight() / 4));

                if (x + width > getWidth()) {
                    x = getWidth() - width;
                }
                if (y + height > getHeight()) {
                    y = getHeight() - height;
                }

                Color color = new Color(
                        (int) (Math.random() * 255),(int) (Math.random() * 255),(int) (Math.random() * 255));

                lstShapes.add(new MyRectangle(x,width,height,color));
                repaint();
            }
        });
        populate.setInitialDelay(0);
        populate.setRepeats(true);
        populate.setCoalesce(true);

        addMouseListener(new MouseAdapter() {
            @Override
            public void mousePressed(MouseEvent e) {
                populate.restart();
            }

            @Override
            public void mouseReleased(MouseEvent e) {
                populate.stop();
            }
        });

    }

    @Override
    protected void paintComponent(Graphics g) {

        super.paintComponent(g);

        Graphics2D g2d = (Graphics2D) g;
        for (MyRectangle rect : lstShapes) {
            rect.paint(g2d);
        }

        FontMetrics fm = g2d.getFontMetrics();
        String text = Integer.toString(lstShapes.size());

        g2d.setColor(getForeground());
        g2d.drawString(text,getWidth() - fm.stringWidth(text),getHeight() - fm.getHeight() + fm.getAscent());

    }

    public class MyRectangle extends Rectangle {

        private Color color;

        public MyRectangle(int x,int width,int height,Color color) {
            super(x,height);
            this.color = color;
        }

        public Color getColor() {
            return color;
        }

        public void paint(Graphics2D g2d) {

            g2d.setColor(getColor());
            g2d.fill(this);

        }
    }
}