如何连续添加到ArrayList

Question

我在这里试图实现的是，当用户选择ComboBox中的数据时，它会将其与我的HashMap匹配，并将其添加到ArrayList中。

public class Stuffs {

Stuffs(){
    
    //Creating HashMap
    HashMap<String,String> map = new HashMap<>();
    map.put("LOTR 1", "The Fellowship of the Ring");
    map.put("LOTR 2", "The Two Towers");
    map.put("LOTR 3", "The Return of the King");
    
    //Creating frame
    JFrame f = new JFrame();
    f.setSize(500, 500);
    f.setVisible(true);
    
    //Creating combobox
    String choices[] = {"LOTR 1","LOTR 2","LOTR 3"};
    JComboBox cb = new JComboBox(choices);
    cb.setBounds(50, 50,90,20);
    f.setLayout(null);    
    f.setSize(300,300);
    f.add(cb);

    //Creating button
    JButton btn = new JButton("OK");
    btn.setBounds(100,100,70,20); 
    f.add(btn);
    
    
    //Get selected item from HashMap and add into arraylist
    btn.addActionListener(new ActionListener(){
        public void actionPerformed(ActionEvent e){
        
        ArrayList test = new ArrayList<>();
        String x = (String) cb.getSelectedItem();
        String y = map.get(x);
        Collections.addAll(test, x, y);
        System.out.println(test);
        }
    });
    
}

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

代码有效。输出为：

[LOTR 1, The Fellowship of the Ring] 

（用户从组合框中选择了 LOTR 1）

但是当我再次单击该按钮时，ArrayList会重置。我想要的是让ArrayList继续添加数据而不替换初始数据，即使它是重复的。例如：

[LOTR 1, The Fellowship of the Ring, LOTR 2, The Two Towers]

基本上，用户可以从ComboBox中选择无数次，ArrayList不断添加和添加。