一个关于重构的问题，求助(增加Code标签)

近日由于工作原因，需要写一个读取文件的类，目的是读取日志文件中的一条记录。由于近20分钟内的数据可能不准，所以每次都读20分钟之前的数据。如果读取发生错误，则写入日志文件。比如现在为9：55分，则取9：35分那条数据。实现如下。现在需要增加一个设定时间，而不是取当前时间的方法，由于深知复制粘贴的错误，故而想重构后抽出相似方法，不过不知从何处下手。初学乍练，请高手不吝赐教。

public class BillingInforByLogImpl implements BillingInforManager {

private Logger logger;

private String billingLogPath;

private BillingStringTransform billingStringTransform;

private ExceptionFileWriter exceptionFileWriter;

private static final int TIME_BASE = 1000;

private static final int CALENDAR_MINUTE_SET = 12;

private static final int CUT_MINUTE = -20;

public BillingInfor queryBillingInfor( 
ChannelContraposeInfor channelContraposeInfor) throws IOException { 
PropertyConfigurator.configure("conf" + File.separator 
+ "log4j.properties"); 
logger = Logger.getRootLogger();

String fileName = getFileName(channelContraposeInfor.getIp(), 
channelContraposeInfor.getInOid()); 
logger.info("Read log is " + fileName);

File file = new File(fileName);

FileInputStream fileInputStream; 
try { 
fileInputStream = new FileInputStream(file); 
} catch (FileNotFoundException e) { 
writExceptionFile(channelContraposeInfor, " ", e.getMessage()); 
logger 
.error("BillingInforByLogImpl.queryBillingInfor|Can't find log file :" 
+ fileName); 
throw new IOException(e.getMessage()); 
}

return queryBillingInforFromLogFile(channelContraposeInfor, 
fileInputStream); 
}

private void writExceptionFile( 
ChannelContraposeInfor channelContraposeInfor, 
String billingResult, String errorFlag) throws IOException { 
SimpleDateFormat simpleDateFormat = new SimpleDateFormat("yyyyMMddhhmm"); 
exceptionFileWriter.appendExceptionFile(channelContraposeInfor, 
simpleDateFormat.format(new Date()), billingResult, errorFlag); 
}

private BillingInfor queryBillingInforFromLogFile( 
ChannelContraposeInfor channelContraposeInfor, 
FileInputStream fileInputStream) throws IOException { 
BufferedReader allFileLines = new BufferedReader(new InputStreamReader( 
fileInputStream)); 
try { 
String oneLine; 
while ((oneLine = allFileLines.readLine()) != null) { 
if (oneLine != null) { 
String[] oneLineStrings = oneLine.split(" "); 
if (oneLineStrings.length != 5 
|| !isNowTimeAddTenMinutesAfterFileTime(oneLineStrings[0])) { 
continue; 
} 
logger.info("File fist line is: " + oneLine); 
return billingStringTransform.transformBillingString( 
channelContraposeInfor.getChannelID(), 
oneLineStrings[1], oneLineStrings[2],oneLineStrings[0]); 
} 
} 
} catch (Exception e) { 
logger 
.error("BillingInforByLogImpl.queryBillingInfor|Analyse log file error :" 
+ e.getMessage()); 
writExceptionFile(channelContraposeInfor, " ", e.getMessage()); 
throw new IOException(e.getMessage()); 
} 
writExceptionFile(channelContraposeInfor, " ", 
"Log file is no hava log infor"); 
throw new IOException( 
"BillingInforByLogImpl.queryBillingInfor|Log file is no hava log infor"); 
}

private boolean isNowTimeAddTenMinutesAfterFileTime(String time) { 
GregorianCalendar fileTime = new GregorianCalendar(); 
GregorianCalendar thisTime = new GregorianCalendar(); 
Date date = new Date(Long.valueOf(time) * TIME_BASE);

thisTime.setTime(new Date()); 
fileTime.setTime(date);

thisTime.add(CALENDAR_MINUTE_SET, CUT_MINUTE); 

if (thisTime.after(fileTime)) { 
return true; 
} 
return false; 
}

private String getFileName(String ip, String oid) { 
String[] flag = oid.split("\\."); 
return billingLogPath + File.separator + ip + "_" + flag[10] + ".old"; 
}

public void setBillingLogPath(String billingLogPath) { 
this.billingLogPath = billingLogPath; 
}

public void setBillingStringTransform( 
BillingStringTransform billingStringTransform) { 
this.billingStringTransform = billingStringTransform; 
}

public void setExceptionFileWriter(ExceptionFileWriter exceptionFileWriter) { 
this.exceptionFileWriter = exceptionFileWriter; 
}

感觉需求不明确啊，问个 问题：
这个设定时间的方法，什么作用，设定的时间怎么用？