java - 文件处理在第二次使用后删除记录

Question

当我第二次运行该程序时，我的 Record.txt 变空。

我认为我在文件阅读器中收到此错误，但我不知道该如何处理它。

如果你们能给我一个提示，我将不胜感激。

File file = new File("D:\\Program Files\\Oracle\\program\\Record.txt");
if (file.length() <= 0) {
    try {

        FileReader fr = new FileReader(
                "D:\\Program Files\\Oracle\\program\\inventory.txt");
        BufferedReader br = new BufferedReader(fr);
        String datas = "";

        while ((datas = br.readLine()) != null) {
            String[] d = datas.split(",");
            int a = Integer.parseInt(d[1]);
            int b = Integer.parseInt(d[2]);
            items.add(new list(d[0], a, b));

        }
        br.close();
        fr.close();

    } catch (IOException | NumberFormatException e) {
        System.out.println("Error");
    }
}

    Iterator itemit = items.iterator();
    try {
        FileWriter fw = new FileWriter(
                "D:\\Program Files\\Oracle\\program\\Record.txt");
        BufferedWriter bw = new BufferedWriter(fw);
        itemit = items.iterator();
        while (itemit.hasNext()) {
            list l = (list) itemit.next();
            System.out.println(l.ingname + l.qty + l.ingid);
            if (item1 == 1 && l.ingid == 100) {
                l.qty = l.qty - item1qty;
            }
            if (item2 == 1 && l.ingid == 200) {
                l.qty = l.qty - item2qty;
            }
            bw.write(l.ingname + ":" + l.qty + ":" + l.ingid);
            bw.newLine();

        }
        bw.close();
        fw.close();
    } catch (IOException e) {
        System.out.println("Error");
    }
else{
            try{
                FileReader fr = new FileReader("D:\\Program Files\\Oracle\\program\\Record.txt");
                   BufferedReader br = new BufferedReader(fr);
                   String datas = "";

                   //System.out.println(file.length());
                   while((datas = br.readLine()) != null){
                       String[] d = datas.split(",");
                       int x = Integer.parseInt(d[1]);
                       items.add(new list(d[0],x));


                   }
                   br.close();
                   fr.close();
            }catch(IOException | NumberFormatException e){
                System.out.println("Error");
            }
        }

Answer 1

从您提供的代码部分来看，如果Record.txt文件为空。如果它不为空(例如第二次运行程序时)，items 可能为空，因此 Record.txt 的内容将被覆盖。

目前您的代码如下所示

if (Record.txt file is emtpy) {
   read inventory file into items
}

write items to record file

// where is the corresponding if?!
else {
   read Record.txt file
}

大概应该是这样的

if (Record.txt file is emtpy) {
   read inventory file into items
   write items to record file
}
else {
   read Record.txt file
}