java - 如何向文本文件添加行号？

Question

所以我需要编写一个程序来读取包含文本的文件，然后向每行添加行号。到目前为止，我打印出行号，但不是只打印出每一行，而是打印每行中的所有文本。我怎样才能拥有它以便打印出该行？

这是我到目前为止的代码:

public static void main(String[] args) throws FileNotFoundException {
    try {
        ArrayList<String> poem = readPoem("src\\P7_2\\input.txt");
        number("output.txt",poem);
    }catch(Exception e){
        System.out.println("File not found.");
    }
}

public static ArrayList<String> readPoem(String filename) throws FileNotFoundException {
    ArrayList<String> lineList = new ArrayList<String>();
    Scanner in = new Scanner(new File(filename));
    while (in.hasNextLine()) {
        lineList.add(in.nextLine());
    }
    in.close();
    return lineList;
}
public static void number (String filename,ArrayList<String> lines) throws FileNotFoundException{
    PrintWriter out = new PrintWriter(filename);
    for(int i = 0; i<lines.size(); i++){
        out.println("/* " + i + "*/" + lines);
    }
    out.close();
}

Answer 1

这是使用 Java 7 提供的新功能的程序的较短版本；它假设您有一个足够短的源文件:

final Charset charset = StandardCharsets.UTF_8;
final String lineSeparator = System.lineSeparator();

final Path src = Paths.get("src\\P7_2\\input.txt");
final Path dst = Paths.get("output.txt");

try (
    final BufferedWriter writer = Files.newBufferedWriter(src, charset, StandardOpenOption.CREATE);
) {
    int lineNumber = 1;
    for (final String line: Files.readAllLines(src, charset))
        writer.write(String.format("/* %d */ %s%s", lineNumber++, line, lineSeparator));
    writer.flush();
}