Question

class blabla extends JPanel
{
    public blabla()
    {
    //code
    }
}

class Main
{
    public static void main(String[] args)
    {
        JPanel b;
        ArrayList<blabla> c;

        blabla a = new blabla();

        b = new JPanel();
        c = new ArrayList<blabla>();

        b.add(a);
        c.add(a);

        blabla d = (blabla) b.getComponent(0);
        System.out.println(c.indexOf(d));
     }
}

Are ArrayList a and JPanel a same objects?
What should be the codes output?

Answer 1

Alright here goes the answer for your modified question…

Are ArrayList a and JPanel a same objects?

No. But they contain the same object of class blabla.

What should be the codes output?

The output is

0

which is right as you placed the same component in the JPanel and ArrayList and 0 is the index of element.