GridBagLayout gbl = new GridBagLayout();
    container.setLayout(gbl);
    
    // Add components to container and gbl
    
    // Force the layout of components before calling getLayoutDimensions()
    gbl.layoutContainer(container);
    
    // Get the dimensions
    int[][] dim = gbl.getLayoutDimensions();
    int cols = dim[0].length;
    int rows = dim[1].length;