Question

java为文件添加行号题

给已经存在的.txt文本文件添加行号。此文件已经用文本编辑完毕，保存在d:\file目录中，命名为hello.txt

Answer 1

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

public class Test{
public static void main(String[] args){
List<String> list=new ArrayList<String>();
try {
File f=new File("d:/file/hello.txt ");
Scanner sc=new Scanner(f);
int k=0;
while(sc.hasNextLine()){
list.add(++k+" "+sc.nextLine());
}
FileWriter fw=new FileWriter(f);
for(int i=0;i<list.size();i++)
fw.write(list.get(i)+"\r\n");
fw.flush();
fw.close();
System.out.println("操作已经成功完成！");

} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
}
}

Answer 2

public class TxtTest {

public static void main(String[] args) {
try {
File file = new File("d:\\file\\hello.txt");
FileReader reader = new FileReader(file);
BufferedReader bReader = new BufferedReader(reader);
ArrayList<String> list = new ArrayList<String>();
String temp = "";
int n = 0;
bp:
while (true) {
temp = bReader.readLine();
if (temp == null) {
break bp;
}
temp = n + " " + temp ;
n++;
list.add(temp);
}
bReader.close();
reader.close();
file.delete();
file.createNewFile();
FileWriter writer = new FileWriter(file);
BufferedWriter bWriter = new BufferedWriter(writer);
for (int i = 0; i < list.size(); i++) {
bWriter.write(list.get(i));
bWriter.newLine();
}
bWriter.flush();
} catch (Exception ex) {
Logger.getLogger(TxtTest.class.getName()).log(Level.SEVERE, null, ex);
}
}
}
这个比较机械，运行一次就会加一次，不会判断是否已经有行号的。

Answer 3

用LineNumberReader读文件
它有一个getLineNumber()方法

Answer 4

#!/bin/sh
cat -n hello.txt >> tmp
rm hello.txt
cat tmp >> hello.txt
rm tmp

Answer 5

你说的编辑行号是什么意思？可以说具体点么？