如何从JFrame中删除最大化和最小化按钮？

import java.awt.event.WindowAdapter;import java.awt.event.WindowEvent;import javax.swing.JDialog;import javax.swing.Jframe;import javax.swing.JLabel;import javax.swing.JPanel;public class Dlg extends JDialog {    public Dlg(Jframe frame, String str) {        super(frame, str);        addWindowListener(new WindowAdapter() { public void windowClosing(WindowEvent evt) {     System.exit(0); }        });    }    public static void main(String[] args) {        try { Dlg frame = new Dlg(new Jframe(), "No min max buttons"); JPanel panel = new JPanel(); panel.setSize(200, 200); JLabel lbl = new JLabel("blah blah"); panel.add(lbl); frame.add(panel); frame.setSize(400, 400); frame.setVisible(true);        } catch (IllegalArgumentException e) { System.exit(0);        }    }}