出于某种原因使用FileWriter和BufferedWriter清除文件？ [英] Using FileWriter and BufferedWriter clearing file for some reason?

问题描述

出于某种原因，当我在我的程序中创建一个新的BufferedWriter和FileWriter时（即使我还没有使用它来编写任何内容），它会清除我选择的所有文本的文件。

For some reason, when I create a new BufferedWriter and FileWriter in my program (Even if I haven't used it to write anything yet), it clears the file I have selected of all it's text.

selectedFile由JFileChooser决定。

selectedFile is determined by a JFileChooser.

public static File selectedFile;

    public static void Encrypt() throws Exception {

    try {
        //if I comment these two writers out the file is not cleared.
        FileWriter fw = new FileWriter(selectedFile.getAbsoluteFile());
        BufferedWriter bw = new BufferedWriter(fw);

        List<String> lines = Files.readAllLines(Paths.get(selectedFile.toString()),
                Charset.defaultCharset());
        for (String line : lines) {
            System.out.println(line);
            System.out.println(AESencrp.encrypt(line));

            /*file is cleared regardless of whether or not these are commented out or
             * not, as long as I create the new FileWriter and BufferedWriter the file
             * is cleared regardless.*/

            //bw.write(AESencrp.encrypt(line));
            //bw.close();
        }
    } catch (IOException e) {
        e.printStackTrace();
    }
}

AESencrp.encrypt只是我的加密类，它不会影响它。如果我创建一个新的FileWriter和BufferedWriter，那么这个循环甚至不会运行（至少我不相信，因为我没有得到行的加密或打印文件的原始内容，如果我没有打印那么打印t创建了新的FileWriter / BufferedWriter。）

AESencrp.encrypt is just an encrypting class I have, it won't affect it. If I create a new FileWriter and BufferedWriter then this loop isn't even run (At least I do not believe so, as I don't get the encryption of line or the original contents of the file printed, which prints if I haven't created the new FileWriter/BufferedWriter.)

        for (String line : lines) {
            System.out.println(line);
            System.out.println(AESencrp.encrypt(line));

            /*file is cleared regardless of whether or not these are commented out or
             * not, as long as I create the new FileWriter and BufferedWriter the file
             * is cleared regardless.*/

            //bw.write(AESencrp.encrypt(line));
            //bw.close();
        }

推荐答案

这是因为构造函数 FileWriter 如果文件已存在，则使用截断文件。

This is because the constructor of FileWriter you are using truncates the file if it already exists.

如果要添加数据，请使用：

If you want to append the data instead, use:

new FileWriter(theFile, true);

这篇关于出于某种原因使用FileWriter和BufferedWriter清除文件？的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！