urenraintity arrayList存儲

Question

public void openFile(){ 
     try { 
      l = new Formatter("try.txt"); 
      System.out.println("Opened File"); 
     } catch (Exception e){ 
      System.out.println("Did not open file"); 
     } 
    } 
    public void addRecord(){ 
     l.format("%s", nameField.getText()); 
     System.out.println("Added Name" + " " + nameField.getText()); 
     } 
    public void onClose(){ 
     l.close(); 
    } 

/* 

So I am trying to store user data, I have a gui and anytime they click sign up i want to store the namefield in an array list, is it possible that anytime I close and reopen the program and someone else puts in their name it just adds to the array list instead of overriding what the earlier person put in? 
Example is in my gui i type in mike as name, I close it and reopen it and put in john as the name, would that add mike and john or would it be just john? and how do I make them co-exist? 
Thank you 

它將其讀取到文件中，但每次關閉該程序並再次運行它時，它將替換第一行中的任何內容。

Answer 1

使用List（其中ArrayList是一個實現），您可以使用add方法。例如，如果您有一個包含單個對象的列表「Mike」，然後執行namesList.add("John")（其中namesList是List<String>），那麼列表將包含兩個元素：「John」和「Mike」。

但是，您還提到程序執行之間的持久數據。默認情況下，所有列表純粹是在內存數據存儲，並且將在每次關閉並重新打開程序時清除。要存儲它們，你需要某種形式的數據持久性。在重頭上，這將是一個完整的數據庫，但對於一個簡單需求的小項目，您可以使用SQLite - 甚至只是一個文本文件。