Why can't a class extending JTextField instantiate a JPasswordField?

Question

I have an empty class MyJTextField extending JTextField, and I want MyJTextField to be initialized as JPasswordField, like JTextField can do.

JTextField pass = new JPasswordField(); //no errors
but
MyJTextField pass = new JPasswordField();//"Type mismatch: cannot convert from JPasswordField to MyJTextField"

Answer 1

Your MyJTextField is a child of JTextField. And JPasswordField also is a child of JTextField. But MyJTextField is not a child of JPasswordField, so MyJTextField is not a JPasswordField, they are siblings.

    //you can do
    JTextField field1 = new JPasswordField(); //child is an instance of parent
    JTextField field2 = new MyJTextField(); //child is an instance of parent

    //you can't do
    JPasswordField field3 = new JTextField(); // parent is not instance of child
    MyJTextField field4 = new JTextField(); // parent is not instance of child
    JPasswordField field5 = new MyJTextField(); // siblings are not instances of each other
    MyJTextField field6 = new JPasswordField(); // siblings are not instances of each other