Adding JPanel to JFrame

Question

I have a program in which a JPanel is added to a JFrame:

public class Test{

    Test2 test = new Test2();
    JFrame frame = new JFrame();

    Test(){

    ...         


        

Answer 1

Your Test2 class is not a Component, it has a Component which is a difference.

Either you do something like

frame.add(test.getPanel() );

after you introduced a getter for the panel in your class, or you make sure your Test2 class becomes a Component (e.g. by extending a JPanel)