JButton dosen't generat random string from ArrayList

I want a new string from my Array to show in console everytime i press the button in JFrame. However, when i press the button in JFrame it only show me 1 string that dosen't change. please help!

And sorry for my bad english, i'm from Sweden

Here is my code:

private JFrame frame;
private JPanel panel;
private JButton rand;
private String random;

public Start() {

    frame = new JFrame("Java Jar exec");
    frame.setVisible(true);
    frame.setSize(450, 305);
    frame.setLocation(610, 300);
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    frame.setResizable(false);


    panel = new JPanel();
    panel.setLayout(null);


    rand = new JButton("Rand");
    rand.setBounds(10, 10, 10, 10);
    rand.addActionListener(this);
    rand.setActionCommand("rand");
    rand.addMouseListener(this);


    panel.add(rand);
    frame.add(panel);




    ArrayList<String>arr = new ArrayList <String>();
    arr.add("1");
    arr.add("2");
    arr.add("3");
    arr.add("4");


random = arr.get(new Random().nextInt(arr.size()));



}




@Override
public void actionPerformed(ActionEvent e) {

    String name = e.getActionCommand();

    if (name.equals("rand")) {
        System.out.print(random + '\n');



    }

}

There is more code, but this is the only important.