输出文档（txt）的行号

import java.io.*;

/**
* Created by Administrator on 2017/3/30.
*/
class LineNum extends BufferedReader{
int count = 1;

public LineNum(Reader in) {
super(in);
}
//复写BufferedReader的readLine()方法
@Override
public String readLine() throws IOException {
String line = super.readLine();
if(line == null){
return null;
}
line = count + " " + line;//输出：行号 + 一个空格 + 每行的文本
count++;
return line;
}
}
public class LineNumTest {
public static void main(String[] args) throws IOException {
File file = new File("E:\\test.txt");//需要读取的文本
FileReader fileReader = new FileReader(file);//建立读取文本的通道
LineNum lineNum = new LineNum(fileReader);//使用lineNum类
String content = null;
while ((content = lineNum.readLine()) != null){
System.out.println(content);
}
lineNum.close();//关闭数据流
}
}