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

public class Test{

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

Test(){
...
frame.setLayout(new BorderLayout());
frame.add(test, BorderLayout.CENTER);
...
}

//main
...
}

//public class Test2{
public class Test2 extends JPanel {

//JPanel test2 = new JPanel();

Test2(){
...
}