java BufferedReader 定位读取文件内容

import java.io.BufferedReader;import java.io.File;import java.io.FileInputStream;import java.io.IOException;import java.io.InputStreamReader;public class Test {/** * @param args */public static void main(String[] args) throws IOException {long t1 = System.currentTimeMillis();File f = new File("F://LoginAction.java");InputStreamReader reader = new InputStreamReader(new FileInputStream(f),"UTF-8");BufferedReader bf = new BufferedReader(reader);        int i = 0 ;        String line = "";        while (( line = bf.readLine())!=null) {        ++i;        if(i==7923){        System.out.println(line);         break;        }        }            bf.close();        reader.close();        long t2 = System.currentTimeMillis();        System.out.println("读取用时："+(t2-t1)+"毫秒");}}