java - Java 中的文件分割代码未按要求工作

Question

我尝试了以下文件分割代码，它可以工作，但不符合要求。即，一个名为“song.mp3”的 mp3 文件大小为 2540KB，预期 block 数(每个 100KB)为 25，但代码仅给出 12 个 block ，我不明白原因。

        public static void main(String[] args) throws IOException {

              File file = new File("song.mp3");

    FileInputStream fIn = new FileInputStream("song.mp3");
    FileOutputStream fOut = new FileOutputStream("song_0.mp3");
    int chunk_size = 1024 * 100;
    byte[] buff = new byte[chunk_size]; // 100KB file
    int i = 0;
    String file_name = file.getName();
    String file_name_base = file_name.substring(0, 
    file_name.lastIndexOf("."));
    while (fIn.read() != -1) {

        fIn.read(buff);
        int total_read = 0;
        total_read += chunk_size;
        long read_next_chunk = total_read;
        String file_name_new = file_name_base + "_" + i + ".mp3";
        File file_new = new File(file_name_base);
        i++;
        fOut = new FileOutputStream(file_name_new);
        fOut.write(buff);

        fIn.skip(total_read);// skip the total read part

    } // end of while loop

    fIn.close();
    fOut.close();

}

Answer 1

您的代码肯定不起作用，至少是因为:
在每次迭代中，您都会读取 1 个字节，并通过 while (fIn.read() != -1) 将其丢弃。
将循环更改为如下所示:

int bytesReadCounter;
while((bytesReadCounter = fIn.read(buff, 0, chunk_size)) > 0){
    .................................. 
    fOut.write(buff, 0, bytesReadCounter);
    ..................................
}

在 buff 中存储读取的字节数，在 bytesReadCounter 中存储读取的字节数。
然后，您从 buff 写入 fOut，恰好是 bytesReadCounter 字节。

编辑，使用此代码:

public static void main(String[] args) {
    File file = new File("song.mp3");

    FileInputStream fIn = null;
    try {
        fIn = new FileInputStream(file);
    } catch (FileNotFoundException e) {
        e.printStackTrace();
    }

    int chunk_size = 1024 * 100;
    byte[] buff = new byte[chunk_size]; // 100KB file
    int i = 0;
    String file_name = file.getName();
    String file_name_base = file_name.substring(0, file_name.lastIndexOf("."));
    int bytesReadCounter;
    boolean hasMore = true;
    while (hasMore) {
        try {
            bytesReadCounter = fIn.read(buff, 0, chunk_size);
        } catch (IOException e) {
            e.printStackTrace();
            break;
        }

        hasMore = bytesReadCounter > 0;

        if (!hasMore)
            break;

        String file_name_new = file_name_base + "_" + i + ".mp3";
        File file_new = new File(file_name_new);

        FileOutputStream fOut = null;
        try {
            fOut = new FileOutputStream(file_new);
        } catch (FileNotFoundException e) {
            e.printStackTrace();
            break;
        }

        try {
            fOut.write(buff, 0, bytesReadCounter);
            fOut.close();
        } catch (IOException e) {
            e.printStackTrace();
            break;
        }

        i++;
    }

    try {
        fIn.close();
    } catch (IOException e) {
        e.printStackTrace();
    }
}