java i/o BufferedWriter 出现漏读数据的问题

Question

public void Writerdemo(){ double startime = System.currentTimeMillis(); String s1="F:/tt.txt";String  str = "imooc"; File file =new File(s1); if(file.exists()){}else{ try { file.createNewFile(); } catch (IOException e) { e.printStackTrace(); } } String id=null; int n=1; try { FileWriter fw = new FileWriter(file,true); BufferedWriter bufw = new BufferedWriter(fw); for(int i=1;i<1000;i++){ if(i%99==0){ s1="F:/tt"+n+".txt"; bufw = new BufferedWriter(new FileWriter(new File(s1),true)); n++; } id= "ID:"+i+"\t"; String s = id+str; bufw.write(s); bufw.newLine();//换行 } bufw.close(); fw.close(); } catch (FileNotFoundException e) { e.printStackTrace(); } catch (IOException e) { e.printStackTrace(); } double endtime = System.currentTimeMillis(); System.out.println("程序运行时间："+(endtime-startime)/1000+"秒"); }程序运行后每个文件之间总有十几条或几十条数据没有了，不知道什么出问题了 ，求指教！！