Line up swing components by edges

Question

Is it possible to line up swing components? The components are in separate panels which both use flow layout. These two panels are in another panel which is using a grid layout.

As you can see there is a subtle difference and I find it annoying. I know that all of the jlabels [the rectangles in blue/purple all have the same size, so i think it might be because of the '+' and '*', but I'm not sure because the left sides of the first two boxes aren't lined up.

the panels

JPanel panel2 = new JPanel(new GridLayout(4, 1));
JPanel panel2a = new JPanel(new FlowLayout());
JPanel panel2b = new JPanel(new FlowLayout());

the first two rectangles (purple)

add1 = new JLabel("", JLabel.CENTER);
add1.setTransferHandler(new TransferHandler("text"));
add1.setBorder(b2);
add2 = new JLabel("", JLabel.CENTER);
add2.setTransferHandler(new TransferHandler("text"));
add2.setBorder(b2);

the two blue rectangles

textFieldA = new JTextField();
textFieldA.setHorizontalAlignment(JTextField.CENTER);
textFieldA.setEditable(false);
textFieldA.setBorder(new LineBorder(Color.blue));
textFieldM = new JTextField();
textFieldM.setHorizontalAlignment(JTextField.CENTER);
textFieldM.setEditable(false);
textFieldM.setBorder(new LineBorder(Color.blue));

the + and *

opA = new JLabel("+", JLabel.CENTER);
opS = new JLabel("*", JLabel.CENTER);

Showing that the rectangles are the same size

Dimension d = card1.getPreferredSize(); 
int width = d.width + 100;
int height = d.height + 50;

add1.setPreferredSize(new Dimension(width, height));
add2.setPreferredSize(new Dimension(width, height));
mult1.setPreferredSize(new Dimension(width, height));
mult2.setPreferredSize(new Dimension(width, height));

textFieldA.setPreferredSize(new Dimension(width, height));
textFieldM.setPreferredSize(new Dimension(width, height));

Adding to the panels

panel2a.add(add1);
panel2a.add(opA);
panel2a.add(add2);
panel2a.add(enterA);
panel2a.add(textFieldA);
panel2c.add(mult1);
panel2c.add(opM);
panel2c.add(mult2);
panel2c.add(enterM);
panel2c.add(textFieldM);
panel2.add(panel2a);
panel2.add(panel2c);

Answer 1

AFAIU this could be achieved using GroupLayout. This layout would require 5 horizontal groups and 2 vertical groups.

See How to Use GroupLayout for examples (including discussion of that image).

See also this answer for an MCVE.

Answer 2

Cross container layout management isn't really possible (or at least I've never seen a layout manager that does it).

You can, however, think carefully about your layout requirements and produce some interesting effects using compound components and layout managers...

public class TestLayout {

    public static void main(String[] args) {
        new TestLayout();
    }

    public TestLayout() {
        EventQueue.invokeLater(new Runnable() {
            @Override
            public void run() {
                try {
                    UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
                } catch (ClassNotFoundException ex) {
                } catch (InstantiationException ex) {
                } catch (IllegalAccessException ex) {
                } catch (UnsupportedLookAndFeelException ex) {
                }

                JFrame frame = new JFrame();
                frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                frame.setLayout(new GridLayout(2, 0));
                frame.add(new CalculatePane("+"));
                frame.add(new CalculatePane("x"));
                frame.pack();
                frame.setLocationRelativeTo(null);
                frame.setVisible(true);
            }
        });
    }

    public class CalculatePane extends JPanel {

        public CalculatePane(String operator) {
            setLayout(new GridBagLayout());
            Font font = UIManager.getFont("TextField.font").deriveFont(Font.BOLD, 24);
            JTextField field1 = new JTextField(2);
            JTextField field2 = new JTextField(2);
            JTextField field3 = new JTextField(2);
            field1.setFont(font);
            field2.setFont(font);
            field3.setFont(font);

            GridBagConstraints gbc = new GridBagConstraints();
            gbc.gridx = 0;
            gbc.gridy = 0;
            gbc.insets = new Insets(2, 2, 2, 2);
            gbc.fill = GridBagConstraints.BOTH;
            add(field1, gbc);
            gbc.gridx++;
            add(new JLabel(operator), gbc);
            gbc.gridx++;
            add(field2, gbc);
            gbc.gridx++;
            gbc.fill = GridBagConstraints.HORIZONTAL;
            add(new JButton("="), gbc);
            gbc.fill = GridBagConstraints.BOTH;
            gbc.gridx++;
            add(field3, gbc);


        }

    }

}