JFrame：如何禁用窗口大小调整？

我正在创建一个，我调用该方法。现在，期望的行为是用户在任何情况下都不应调整 JFrame 的大小。通过最大化或拖动边框。它应该是 500x500。我该怎么做？我还附上了代码，以防您可以更好地指导我。JFramesetSize(500, 500)

    package com.techpapa;    
    import javax.swing.*;  
    import java.awt.*;  
    import java.awt.event.*;  

    public class MainWindow extends JFrame{


private JTextField
            write;
private JRadioButton
            rb1,
            rb2,
            rb3;
private ButtonGroup
            bg;

private ActionListener al = new ActionListener(){
    public void actionPerformed(ActionEvent e){
        write.setText("JRadioButton : " + ((JRadioButton)e.getSource()).getText());
    }

};

public MainWindow(){
    //Frame Initialization
    setSize(500, 500);
    setDefaultCloseOperation(EXIT_ON_CLOSE);
    setLayout(null);
    setTitle(".:JRadioButton:.");
    setVisible(true);

    //Components Initialization
    write = new JTextField(20);
    write.setEditable(false);
    rb1 = new JRadioButton("Male", false);
    rb1.addActionListener(al);
    rb2 = new JRadioButton("Female", false);
    rb2.addActionListener(al);
    rb3 = new JRadioButton("I don't want to specify", true);
    rb3.addActionListener(al);
    bg = new ButtonGroup();

    //Add radio buttons to buttongroup
    bg.add(rb1); bg.add(rb2); bg.add(rb3);

    //Add to window
    add(write);
    write.setBounds(140, 100, 150, 20);
    write.setDragEnabled(true);
    add(rb1);
    rb1.setBounds(180, 200, 100, 30);
    add(rb2);
    rb2.setBounds(180, 225, 100, 30);
    add(rb3);
    rb3.setBounds(180, 250, 130, 30);

}

public static void main(String[] args) {
    new MainWindow();

}

}