try{
             RandomAccessFile out = new RandomAccessFile(f,"rw");
             out.seek(out.length());      //定位到文件的末尾
             out.writeUTF(s);
             out.close();
             return "内容已成功写入到文件";
             }
         catch(IOException e){
             return "不能写入文件";
         }

 try{
                   RandomAccessFile file = new RandomAccessFile(f,"r");    //只读
                   String temp = null;                                           //*
                   while((temp = file.readUTF()) != null){                  //readUTF()从文件读取一个utf字符
                       byte d[] = temp.getBytes("ISO-8859-1");
                       temp = new String(d);
                       out.print("<br>"+temp);
                       }
                       file.close();