为什么我的文件写入方法不起作用？

Question

This method should write random chars, but it doesn't write anything at all. I'm probably doing something stupidly wrong here, but for the life of me I can't find it.

public void writeRandomChunk(String fileName) {
    try {
        File saveFile = new File(folderName + '/' + fileName);

        PrintWriter writer = new PrintWriter(
                             new BufferedWriter(
                             new FileWriter(saveFile)));

        Random r = new Random(System.currentTimeMillis());

        for (int i = 0; i < chunkSize; i++) {
            for (int j = 0; j < chunkSize; j++) {
                writer.print((char)(r.nextInt(26) + 'a'));
            }
            writer.println();
        }

    } catch (Exception e) {
        System.out.println("Error in WorldFile writeRandomFile:\n"
                           + e.getLocalizedMessage());
    }
}

Answer 1

As with any stream (and this applies to most any language), you need to close it when you are done.

Streams are optimized to be fast, and as a consequence, not all of the data you write to them instantly appears in the file. When you close() or flush() a stream, the data is written to the file (or whatever other storage mechanism you are using).

In your case, try the following, instead.

public void writeRandomChunk(String fileName) {
    PrintWriter writer = null;
    try {
        File saveFile = new File(folderName + '/' + fileName);
        writer = new PrintWriter(
                             new BufferedWriter(
                             new FileWriter(saveFile)));

        Random r = new Random(System.currentTimeMillis());

        for (int i = 0; i < chunkSize; i++) {
            for (int j = 0; j < chunkSize; j++) {
                writer.print((char)(r.nextInt(26) + 'a'));
            }
            writer.println();
        }

    } catch (Exception e) {
        System.out.println("Error in WorldFile writeRandomFile:\n"
                           + e.getLocalizedMessage());
    } finally {
        if (writer != null)
            writer.close();
    }
}

Answer 2

您需要在某个时候冲洗文件和/或关闭文件。

Answer 3

Haven't closed the writer try it in finally.

finally  {
  writer.close();
}

Answer 4

you should always close your stream. try this pattern with writers:

PrinterWriter writer = null;
try {
    writer = new PrinterWriter(...);
    // do your write loop here.
} catch (Exception e) {
    // recover from exception.
} finally {
    if (writer != null) {
        writer.close();
    }
}