IO流(LineNumberReader)

import java.io.*;class LineNumberReaderDemo{    public static void main(String[] args)throws IOException    {        FileReader fr = new FileReader("PersonDemo.java");                 LineNumberReader lnr = new LineNumberReader(fr);                 String line = null;        lnr.setLineNumber(100);        while((line=lnr.readLine())!=null)        {            System.out.println(lnr.getLineNumber()+":"+line);        }        lnr.close();    }} //练习：模拟一个带行号的缓冲区对象