如何讓BufferedWriter寫入文本文件？

Question

我試圖用Java編寫預約書程序，但是BufferedWriter似乎沒有寫入文件。

此代碼是一個try { } catch (FileNotFoundException) { } catch (IOException) { }塊

FileWriter writer = new FileWriter("Appointments" + name + ".txt", true); 
BufferedWriter bufferedWriter = new BufferedWriter(writer); 

if (open == 'o') { 
    FileReader reader = new FileReader("Appointments" + name + ".txt"); 
    BufferedReader bufferedReader = new BufferedReader(reader); 
    while ((line = bufferedReader.readLine()) != null) { 
     if (line.indexOf("one-time") == line.length() - 8) { 
      OneTime o = fromStringOneTime(line); 
      oneTimes.add(o); 
     } 
     if (line.indexOf("daily") == line.length() - 5) { 
      Daily d = fromStringDaily(line); 
      dailys.add(d); 
     } 
     if (line.indexOf("monthly") == line.length() - 7) { 
      Monthly m = fromStringMonthly(line); 
      monthlys.add(m); 
     } 
    } 
} 

的while循環剛初始化所有值的當前在文件分成3周不同的ArrayLists的所有內部。

然後我的代碼來創建新的對象塊，一旦你選擇要添加預約（變量desc和date先前已經被定義）：

System.out.print("Enter if this is a (o)ne-time, (d)aily, or (m)onthly appointment: "); 
freq = scanner.next().charAt(0); 
if (freq == 'o') { 
    OneTime o = new OneTime(desc, date.getDate()); 
    oneTimes.add(o); 
    totalCount++; 
    bufferedWriter.write(o.toString()); 
    bufferedWriter.newLine(); 
    valid = true; 
} else if (freq == 'd') { 
    Daily o = new Daily(desc, date.getDate()); 
    dailys.add(o); 
    totalCount++; 
    bufferedWriter.write(o.toString()); 
    bufferedWriter.newLine(); 
    valid = true; 
} else if (freq == 'm') { 
    Monthly o = new Monthly(desc, date.getDate()); 
    monthlys.add(o); 
    totalCount++; 
    bufferedWriter.write(o.toString()); 
    bufferedWriter.newLine(); 
    valid = true; 
} 

在的結束嘗試塊，我有行reader.close()和writer.close()。那麼爲什麼當我檢查應該保存的文件時，它仍然顯示爲空白？這是我第一次處理文件保存問題，所以我不確定它爲什麼沒有按照應有的方式工作。 。

編輯：如果選擇打開，而不是創建一個新的

Answer 1

是，大多數操作系統不會允許讀取和寫入同一個文件中的現有文件的選項文件將現在只讀。因此，您可以通過寫入臨時文件名的文件來解決此問題，並在程序結束時將其重命名爲原始文件。

try { 
    FileWriter writer = new FileWriter("Appointments" + name + "1.txt", true); 
    FileReader reader = new FileReader("Appointments" + name + ".txt"); 
    BufferedReader bufferedReader= new BufferedReader(reader); 
    BufferedWriter bufferedWriter = new BufferedWriter(writer); 
    ....... 
} catch() { 
    ...... 
} finally { 
    bufferedReader.close(); 
    bufferedWriter.flush(); 
    bufferedWriter.close(); 
} 

// Rename the file and delete temp file 
File srcFile = new File("Appointments" + name + "1.txt"); 
File targerFile = new File("Appointments" + name + ".txt"); 
srcFile.renameTo(targetFile); 
srcFile.delete();