java - 文件写入器和文件读取器错误

Question

我有这段代码可以从文本文件中读取，然后对其进行修改。然后将修改的内容写入到另一个文本文件中。我在 out.write(read); 处遇到空指针异常，而且，并非所有行都被写入，有人可以帮助我吗？谢谢

import java.util.*;
import java.io.*;

public class File
{
    BufferedReader in;
    BufferedWriter out;
    String read;

    public File()
    {
        try {
            in = new BufferedReader(new FileReader("myFile.txt"));
            Scanner scan = new Scanner(in);
            out = new BufferedWriter(new FileWriter("output.txt"));

            while (scan.hasNext()) {
                read = in.readLine();
                //Write codes to modify file here
                //___codes not written yet______//
                out.write(read);
                scan.next();
                System.out.println("file output: " + read);                 
            }
            out.close();
            in.close();
        } catch (IOException e) {
            System.out.println("There was a problem:" + e);
        }
    }

    public static void main(String[] args)
    {
        File File = new File();
    }
}

Answer 1

尝试

while((read = in.readLine()) != null)

而不是

while (scan.hasNext())