title: How to use frame.add method to create multiple visible objects
body: <p>When I try to add a second instance of an elevator class, the first one disappears. How can I rearrange this code in order to see both objects?</p>
  
  <p>Here is my main class:</p>
  
  <pre><code>public class MainClass extends JPanel implements ActionListener {
      public static void main(String[] args) {
          JFrame frame = new JFrame("title");
          frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
          frame.setSize(1000, 700);
          frame.setLocationRelativeTo(null);
          frame.setVisible(true);
  
          Component component1 = frame.add(new elevator(0,0));
          Component component2 = frame.add(new elevator(505,50));   
      }
  
      @Override
      public void actionPerformed(ActionEvent e) {
          // TODO Auto-generated method stub
      }
  }
  </code></pre>
  
  <p>And this is the elevator class:</p>
  
  <pre><code>public class elevator extends JPanel implements ActionListener {
      Timer timer;
      private double angle = 0;
      private double scale = 1;
      private double delta = 0.01;
      private int x=0;
      private int y=0;
  
      Rectangle.Float r = new Rectangle.Float(0, 0, 3, 3);
  
      public elevator(int input_x, int input_y) {
          x=input_x;
          y=input_y;
          timer = new Timer(10, this);
          timer.start();
      }
  
      public elevator() {
          timer = new Timer(10, this);
          timer.start();
      }
  
      public void paint(Graphics g) {
          this.setSize(100,200);
          this.setLocation(x, y);
          int h = getHeight();
          int w = getWidth();
  
          super.paintComponent(g);
  
          Graphics2D g2d = (Graphics2D) g;
  
          g2d.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
          g2d.setRenderingHint(RenderingHints.KEY_RENDERING, RenderingHints.VALUE_RENDER_QUALITY);
  
          g2d.translate(w / 5, scale*140);
          g2d.scale(20, 20);
  
          g2d.fill(r);
      }
  
      public void actionPerformed(ActionEvent e) {
          if (scale &lt; 0.01 || scale &gt; 0.99) {
              delta = -delta;
          } 
          scale += delta;
          angle += 0.01;
          repaint();
      }
  }
  </code></pre>