如何找出用于分割行的BufferedReader#readLine()行分隔符？

Question

我正在通过BufferedReader读取文件

String filename = ...
br = new BufferedReader( new FileInputStream(filename));
while (true) {
   String s = br.readLine();
   if (s == null) break;
   ...
}

我需要知道线条是否以'\n'或'\ r \n'分隔是否有我能找到的方法？

我不想打开FileInputStream以便最初扫描它.理想情况下,我想询问BufferedReader,因为它必须知道.

我很高兴覆盖BufferedReader来破解它,但我真的不想打开文件流两次.

谢谢,

注意:当前行分隔符(由System.getProperty("line.separator")返回)无法使用,因为该文件可能已由另一个应用程序在另一个操作系统上写入.

Answer 1

要与BufferedReader类同步,您可以使用以下方法来处理\n,\ r,\n\r和\ r \n结束行分隔符:

public static String retrieveLineSeparator(File file) throws IOException {
    char current;
    String lineSeparator = "";
    FileInputStream fis = new FileInputStream(file);
    try {
        while (fis.available() > 0) {
            current = (char) fis.read();
            if ((current == '\n') || (current == '\r')) {
                lineSeparator += current;
                if (fis.available() > 0) {
                    char next = (char) fis.read();
                    if ((next != current)
                            && ((next == '\r') || (next == '\n'))) {
                        lineSeparator += next;
                    }
                }
                return lineSeparator;
            }
        }
    } finally {
        if (fis!=null) {
            fis.close();
        }
    }
    return null;
}

Answer 2

在阅读了java文档(我承认自己是一个pythonista)之后,似乎没有一种干净的方法来确定特定文件中使用的行端编码.

我建议的最好的事情是你使用BufferedReader.read()并迭代文件中的每个字符.像这样的东西:

String filename = ...
br = new BufferedReader( new FileInputStream(filename));
while (true) {
   String l = "";
   Char c = " ";
   while (true){
        c = br.read();
        if not c == "\n"{
            // do stuff, not sure what you want with the endl encoding
            // break to return endl-free line
        }
        if not c == "\r"{
            // do stuff, not sure what you want with the endl encoding
            // break to return endl-free line
            Char ctwo = ' '
            ctwo = br.read();
            if ctwo == "\n"{
                // do extra stuff since you know that you've got a \r\n
            }
        }
        else{
            l = l + c;
        }
   if (l == null) break;
   ...
   l = "";
}