這段代碼爲什麼會導致Java寫入文件中的數據？

Question

我不確定爲什麼下面的代碼會導致Java每次都會覆蓋已存在於我的文件中的數據，而當我想要的是實際上將每條新數據寫入新行時。我已經包含了相關的代碼片斷（我知道你可能認爲變量中有錯誤，但是沒有，程序工作正常）。有人可以幫助我理解是什麼導致了這種情況，是我使用文件編寫器的方式嗎？

String DirToWriteFile = System.getProperty("user.dir") + "/VirtualATM.txt"; //Get path to write text file to. 

String Details = "Name: " + name + " CardNo: " + CardNo + " Current Balance: " + balance + " overdraft? " + OverDraft + " OverDraftLimit: " + OverDraftLimit + " pin: " + PinToWrite; 
    try{ 
     //Create writer to write to files. 
     File file = new File(DirToWriteFile); 
     Writer bw = new BufferedWriter(new OutputStreamWriter(new FileOutputStream(file), "UTF8"));   
     // FileReader reads text files in the default encoding. 
     FileReader fileReader = new FileReader("VirtualATM.txt"); 
     // Always wrap FileReader in BufferedReader. 
     BufferedReader bufferedReader = new BufferedReader(fileReader); 
     String CurrentData = ""; 
     while((bufferedReader.readLine()) != null) { 
       line = CurrentData; 
       bw.write(CurrentData); 
       ((BufferedWriter) bw).newLine(); 
     } 
     bw.write(Details); 
     System.out.println("Account created!"); 

     System.out.println(name + " Your card number is: " + CardNo); 
     // close the reader. 
     bufferedReader.close(); 
     //Close the writer. 
     bw.close(); 

Answer 1

使用其他FileOutputStream中構造函數，所述一個接受一個布爾附加參數作爲第二個參數。傳入true，因爲這將告訴Java將文本附加到現有文件而不是覆蓋它。

即，改變該：

File file = new File(DirToWriteFile); 
    Writer bw = new BufferedWriter(new OutputStreamWriter(new FileOutputStream(file), "UTF8"));   

這樣：

File file = new File(DirToWriteFile); 
    FileOutputStream fos = new FileOutputStream(file, true); // **note second param?** 
    Writer bw = new BufferedWriter(new OutputStreamWriter(fos, "UTF8"));