Laying Out Components in a Grid
When components are added to the container, they fill the grid left-to-right, top-to-bottom. 

 
 int rows = 2;
 int cols = 2;
 // The next two lines should be in one line.
 JPanel panel = new JPanel(new GridLayout(
   rows, cols));
 panel.add(component1);
 panel.add(component2);