Jak wyrównać komponenty do środka w JPanel za pomocą GridBagLayout?

Kiedy próbuję wyrównać mój komponent, idzie albo w lewo, albo w prawą stronę.

Chcę tylko, aby rozwiązanie pozbyło się tego problemu, a także powiedz mi, jak ustawić rozmiar panelu na 400 x 350 pikseli.

Oto mój kod ....titleLabel iResultLabel powinny być wyrównane w środku

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);
}
}

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