Wie die align-Komponenten-center in der JPanel mit GridBagLayout?

Wenn ich versuche, richten Sie meine Komponente geht es entweder linken oder rechten Seite.

So, ich will nur die Lösung, um loszuwerden, dieses problem, und mir auch sagen, wie die Größe des panel 400 x 350 pixel.

Hier ist mein code....titleLabel und ResultLabel sollten ausgerichtet werden, in der Mitte

public TimeGui() {

    layout = new GridBagLayout();
    setSize(400, 350);  //**Its not working**
    setBackground(Color.LIGHT_GRAY);
    setBorder(BorderFactory.createLineBorder(Color.BLACK));
    setBorder(new TitledBorder(new EtchedBorder(), "Time Conversion") );

    setLayout(layout);
    layoutConstraints = new GridBagConstraints();       
    textField1 = new JTextField(10);
    textField2 = new JTextField(10);

    String[] names1 = {"Seconds", "Minutes", "Hours", "Days", "Weeks"};


    comboBox1 = new JComboBox<>(names1);
    comboBox2 = new JComboBox<>(names1);

    titleLabel = new JLabel("Time Conversion Unit", JLabel.CENTER);
    resultLabel = new JLabel("Result Label");
    equalLabel = new JLabel("=");

    convertButton = new JButton("Convert");


    layoutConstraints.fill = GridBagConstraints.HORIZONTAL;
    Insets inset = new Insets(10, 10, 10, 10);
    layoutConstraints.anchor = GridBagConstraints.CENTER;

    addComponent(titleLabel, 0, 0, 2, 2, inset ); //I tried (0,1,2,2) 



    addComponent(comboBox1, 3, 0, 2, 3, inset);

    addComponent(comboBox2, 3, 2, 2, 3, inset);

    addComponent(textField1, 6, 0, 1, 2, inset);

    addComponent(equalLabel, 6, 1, 1, 2, inset);

    addComponent(textField2, 6, 2, 1, 2, inset);

    addComponent(resultLabel, 8, 1, 2, 1, inset);

    addComponent(convertButton, 10, 0, 2, 2, inset);

}

private void addComponent(Component component, int row,
        int column, int width, int height, Insets inset1) {
    layoutConstraints.gridx = column;
    layoutConstraints.gridy = row;
    layoutConstraints.gridwidth = width;
    layoutConstraints.gridheight = height;
    layoutConstraints.insets = inset1;
    layout.setConstraints(component, layoutConstraints);
    add(component);
}
}