How can I center exactly one component in a JPanel, while the others remain aligned as default?

So I'm using a main JPanel (Java Swing) and I add a JLabel, a JTextField and a JButton. I'm setting the layout of the main JPanel to BoxLayout.Y_AXIS, aligning all the components in a top to bottom manner. I want my button to be the only one centered, but "submitButton.setAlignmentX(CENTER_ALIGNMENT)" centers everything BUT the button. I tried to encapsulate the button in a JPanel, whose Layout I would change, but I did not succeed.

public NewProductPanel() {
            setLayout(new BoxLayout(this,BoxLayout.Y_AXIS));

            CustomJLabel productNameLabel = new CustomJLabel("PRODUCT NAME:");
            productNameField = new CustomJTextField();

            submitButton = new SubmitButton("Submit");
            submitButton.setAlignmentX(CENTER_ALIGNMENT);

            add(productNameLabel);
            add(productNameField);
            add(submitButton);
        }

A BoxLayout doesn't really work (the way you would expect) when you have components with different x alignment values.

One solution is to use a "wrapper" panel so that all components can have the same x alignment:

setLayout(new BoxLayout(this,BoxLayout.Y_AXIS));

JPanel wrapper = new JPanel();
wrapper.setLayout( new BoxLayout(wrapper, BoxLayout.Y_AXIS) );
wrapper.setAlignmentX(CENTER_ALIGNMENT);

JLabel productNameLabel = new JLabel("PRODUCT NAME:");
productNameLabel.setAlignmentX(LEFT_ALIGNMENT);
JTextField productNameField = new JTextField(10);
productNameField.setAlignmentX(LEFT_ALIGNMENT);

wrapper.add(productNameLabel);
wrapper.add(productNameField);

JButton submitButton = new JButton("Submit");
submitButton.setAlignmentX(CENTER_ALIGNMENT);

add(wrapper);
add(submitButton);

Now the two components on the main panel have the same "center" alignment and the two components of the wrapper panel have the same "left" alignment.

Another option might be to use a GridBagLayout:

setLayout( new GridBagLayout() );
GridBagConstraints gbc = new GridBagConstraints();
gbc.anchor = GridBagConstraints.LINE_START;

JLabel productNameLabel = new JLabel("PRODUCT NAME:");
add(productNameLabel, gbc);

JTextField productNameField = new JTextField(10);
gbc.gridy = 1;
add(productNameField, gbc);

JButton submitButton = new JButton("Submit");
gbc.gridy = 2;
gbc.anchor = GridBagConstraints.CENTER;
add(submitButton, gbc);

Read the Swing tutorial on How to Use GridBagLayout for more information about the contraints.

Or you could use the Relative Layout, which does allow you control alignment of each individual component:

RelativeLayout rl = new RelativeLayout(RelativeLayout.Y_AXIS);
rl.setAlignment( RelativeLayout.COMPONENT );
setLayout( rl );

JLabel productNameLabel = new JLabel("PRODUCT NAME:");
add(productNameLabel);

JTextField productNameField = new JTextField(10);
productNameField.setAlignmentX( LEFT_ALIGNMENT );
add(productNameField);

JButton submitButton = new JButton("Submit");
submitButton.setAlignmentX( CENTER_ALIGNMENT );
add(submitButton);