将JLabel放在JPanel上居中

以下是使组件居中的四种方法：

import java.awt.*;import javax.swing.*;import javax.swing.border.*;class CenterComponent {    public static JLabel getLabel(String text) {        return getLabel(text, SwingConstants.LEFT);    }    public static JLabel getLabel(String text, int alignment) {        JLabel l = new JLabel(text, alignment);        l.setBorder(new LineBorder(Color.RED, 2));        return l;    }    public static void main(String[] args) {        SwingUtilities.invokeLater(new Runnable() { public void run() {     JPanel p = new JPanel(new GridLayout(2,2,4,4));     p.setBackground(Color.black);     p.setBorder(new EmptyBorder(4,4,4,4));     JPanel border = new JPanel(new BorderLayout());     border.add(getLabel(         "Border", SwingConstants.CENTER), BorderLayout.CENTER);     p.add(border);     JPanel gridbag = new JPanel(new GridBagLayout());     gridbag.add(getLabel("GridBag"));     p.add(gridbag);     JPanel grid = new JPanel(new GridLayout());     grid.add(getLabel("Grid", SwingConstants.CENTER));     p.add(grid);     // from @0verbose     JPanel box = new JPanel();     box.setLayout(new BoxLayout(box, BoxLayout.X_AXIS ));     box.add(Box.createHorizontalGlue());     box.add(getLabel("Box"));     box.add(Box.createHorizontalGlue());     p.add(box);     Jframe f = new Jframe("Streeeetch me..");     f.setDefaultCloseOperation(Jframe.EXIT_ON_CLOSE);     f.setContentPane(p);     f.pack();     f.setLocationByPlatform(true);     f.setVisible(true); }        });    }}