Question

我有这段代码从文本文件中读取然后修改它。然后将修改后的内容写入另一个文本文件。我在out.write(read);得到一个空指针异常而且，并非所有的行都被写入，有些人可以帮助我。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())

Answer 2

需要更改：procedure TForm1.Button1Click(Sender: TObject); var Stm: TMemoryStream; begin Stm := TMemoryStream.Create; try Memo.Lines.SaveToStream(Stm); Stm.Position := 0; Memo.Clear; Edit.Text := IntToStr(Integer(@Stm)); except Stm.Free; end; end; procedure TForm1.Button2Click(Sender: TObject); var PStm: ^TMemoryStream; begin PStm := Pointer(StrToInt(Edit.Text)); try Memo.Lines.LoadFromStream(PStm^); // <--- Access Violation finally PStm^.Free; end; end;

文件编写器和文件读取器错误

2 个答案: