java - 更新数据列表时出现问题

Question

private static void deleteProxy(File proxyOld, String host, int port) {
        try {
            String lines, tempAdd;
            boolean removeLine = false;
            File proxyNew = new File("proxies_" + "cleaner$tmp");
            BufferedReader fileStream = new BufferedReader(new InputStreamReader(new FileInputStream(proxyOld)));
            BufferedWriter replace = new BufferedWriter(new FileWriter(proxyNew));
            while ((lines = fileStream.readLine()) != null) {
                tempAdd = lines.trim();
                if (lines.trim().equals(host + ":" + port)) {
                    removeLine = true;
                }
                if (!removeLine) {
                    replace.write(tempAdd);
                    replace.newLine();
                }
            }
            fileStream.close();
            replace.close();
            proxyOld.delete();
            proxyNew.renameTo(proxyOld);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

调用函数:

File x = new File("proxies.txt");//is calling a new file the reason why it's being flushed out?
deleteProxy(x, host, port);

在运行程序之前，文件 proxies.txt 中包含数据。然而，当我运行该程序时，它似乎被冲掉了。它变成空的。

我注意到程序运行时，如果我将鼠标移到文件 proxies.txt 上，Windows 会显示“修改日期” 并且显示的时间为当前时间，或上次执行函数 deleteProxy(...) 的时间。

有人知道我做错了什么吗？为什么列表不会更新而不是显示为空？

更新的代码:

private static void deleteProxy(File proxyOld, String host, int port) {
        try {
            String lines, tempAdd;
            boolean removeLine = false;
            File proxyNew = new File("proxies_" + "cleaner$tmp");
            FileInputStream in = new FileInputStream(proxyOld);
            InputStreamReader read = new InputStreamReader(in);
            BufferedReader fileStream = new BufferedReader(read);
            FileWriter write = new FileWriter(proxyNew);
            BufferedWriter replace = new BufferedWriter(write);

            while ((lines = fileStream.readLine()) != null) {
                tempAdd = lines.trim();
                if (lines.trim().equals(host + ":" + port)) {
                    removeLine = true;
                }
                if (!removeLine) {
                    replace.write(tempAdd);
                    replace.newLine();
                }
            }
            in.close();
            read.close();
            fileStream.close();
            write.close();
            replace.close();

            if (proxyOld.delete()) {
                throw new Exception("Error deleting " + proxyOld);
            }

            if (proxyNew.renameTo(proxyOld)) {
                throw new Exception("Error renaming " + proxyOld);
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

运行更新后的代码可以很好地删除 proxies.txt 但无法创建新文件:\也许我应该找到一种新的方法来更新文本文件，你有什么建议吗？

Answer 1

根据File.renameTo() documentation，您的重命名操作可能不起作用。 :

Many aspects of the behavior of this method are inherently platform-dependent: The rename operation might not be able to move a file from one filesystem to another, it might not be atomic, and it might not succeed if a file with the destination abstract pathname already exists. The return value should always be checked to make sure that the rename operation was successful.

所以基本上，您正在删除旧文件，并且不能保证新文件会取代它。您必须检查File.renameTo()的返回值:

if(proxyNew.renameTo(proxyOld)){
    throw new Exception("Could not rename proxyNew to proxyOld");
}

至于您的 renameTo 可能失败的原因:您没有关闭打开以从旧文件中读取的嵌套流集，因此操作系统可能仍会考虑使用抽象路径名存在。尝试确保关闭所有打开的嵌套流。