java swing关闭窗口没有退出应用程序

import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.WindowConstants;

public class SwingDemo {
    public static void main(String[] args) {
        JFrame frame = new JFrame("Swing Demo");
        frame.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
        frame.add(new JLabel("Hello, Swing!"));
        frame.pack();
        frame.setVisible(true);
    }
}