java实现持续写入内容到txt文件

import java.io.*;import java.util.*;public class LogTest{public static void main(String[] args){File log=new File("user\\log\\login.log");String newLog="UserName:Jim Green  |  Date:"+new Date()+"  |  IP:202.65.21.14";appendLog(log,newLog);}public static void appendLog(File log,String newLog){Scanner sc=null;PrintWriter pw=null;try{if(!log.exists())//如果文件不存在,则新建.{File parentDir=new File(log.getParent());if(!parentDir.exists())//如果所在目录不存在,则新建.parentDir.mkdirs();log.createNewFile();}sc=new Scanner(log);StringBuilder sb=new StringBuilder();while(sc.hasNextLine())//先读出旧文件内容,并暂存sb中;{sb.append(sc.nextLine());sb.append("\r\n");//换行符作为间隔,扫描器读不出来,因此要自己添加.}sc.close();pw=new PrintWriter(new  FileWriter(log),true);/*A.*/pw.println(sb.toString());//,写入旧文件内容./*B.*/pw.println(newLog);//写入新日志./** 如果先写入A,最近日志在文件最后.* 如是先写入B,最近日志在文件最前.*/pw.close();}catch(IOException ex){ex.printStackTrace();}}}