Java将带计算的列添加到CSV文件

如何向CSV文件中添加新列，并在每列中添加计算数据

范例

用户ID，expDate 1,012015 2,022016 3032018

我会从每一行取expDate，计算它相对于当前月份和年份的值，得到它到期的月份数，然后取整MonthsToll，所以下个月的MonthsToll将是1，不管它是当前月份的第一天还是最后一天

userid，expDate，monthsTill 1,022017,0 2,032017,1 3,042017,2 305217,3

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另外，如何跳过在相应列中具有特定值的行？

我还没有对其进行测试，但下面的代码应该可以解决您的问题

List<String> input = FileUtils.readLines(new File("SomeFile"), StandardCharsets.UTF_8);
    List<String> output = new ArrayList<String>();
    if(input.size()>1){
        Calendar cal = Calendar.getInstance();
        cal.setTime(new Date());
        int month = cal.get(Calendar.MONTH) + 1;
        String header = input.get(0) + ",monthsTill";
        output.add(header);
        int length = input.size();
        for(int i=1;i<length;i++){
            StringBuilder str = new StringBuilder();
            String row = input.get(i);
            String [] elements = row.split(",");
            if(elements.length == 2){
             // You have access to both the index and expiry date. So if you want to skip some row, simply don't add it to the ouput collection
                int exp = Integer.parseInt(elements[1].substring(0, 2));
                int monRemaining = month-exp;
                str.append(row).append(",").append(monRemaining);
                output.add(str.toString());
            } else {
                throw new IllegalArgumentException();
            }
        }

        FileUtils.writeLines(new File("SomeFile"), output, false);

与

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当然，如果您不使用ApacheCommonsIO，您将不得不自己处理关闭资源，如streams等

下面是我试图做的一些伪代码

    // read csv file
        // append timeTillExpired to end of first row of CSV
        // for each row after first row
            // calculate timeTillExpired
                // if format MYYYY (ex 22017)
                    // M and YYYY
                    // calculate relative to current date as months
                //else
                    // MM and YYYY (ex 122017)
                    // calculate relative to current date as months
            // if calculated > 3
                // timeTillExpired = ">3"
                // add timeTillExpired to end of row
            //else
                // add timeTillExpired to end of row
    // save file
    // close file

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根据您的伪代码，下面是应该做的事情

private void process(){
    BufferedReader bufferedReader = null;
    PrintWriter p = null;
    String sep = ",";
    String newCol = "monthsTill";
    String defaultTillExpMonth = ">3";
    Calendar cal = Calendar.getInstance();
    cal.setTime(new Date());
    int currMonth = cal.get(Calendar.MONTH) + 1;
    try {
    // read csv file
    List<String> input = new ArrayList<String>();
   File inputFile = new File("InputFile");
  bufferedReader = new BufferedReader(new FileReader(inputFile));
    String readLine = "";
    while ((readLine = bufferedReader.readLine()) != null) {
        input.add(readLine);
    }

 // for each row after first row
    // calculate timeTillExpired
        // if format MYYYY (ex 22017)
            // M and YYYY -> MM and YYYY

       // calculate relative to current date as months

    int numOfRecords = input.size();
    if(numOfRecords>1){
        List<String> output = new ArrayList<String>();
        String header = input.get(0) +sep +newCol;
        output.add(header);

        // for each row after first row
        // calculate timeTillExpired
        // if format MYYYY (ex 22017)
              // M and YYYY -> MM and YYYY
        // calculate relative to current date as months
        for(int i=1;i<numOfRecords;i++){
            // I am simply going to get the last column from record
            String row = input.get(i);
            StringBuilder res = new StringBuilder(row);
            String [] entries = row.split(sep);
            int length = entries.length;
            if(length>0){
                res.append(sep);
                String rec = entries[length-1];
                int expMonth = 0;
                // Case of MYYYY. Assumption is it's either MYYYY or MMYYYY
                if(rec.length()==5){
                    expMonth = Integer.valueOf(rec.substring(0, 1));
                } else {
                    expMonth = Integer.valueOf(rec.substring(0, 2));
                }

                int monToExp = expMonth - currMonth;
                // if calculated > 3
                if(monToExp > 3){
                    res.append(defaultTillExpMonth);
                } else {
                    res.append(monToExp);
                }
                output.add(res.toString());
            }
        }
        // Write into the same file.
        // First We'll delete everything in the input file and then write the modified records

        p = new PrintWriter(new FileWriter("output.txt",false));
        // Ouch. Very bad way to handle resources. You should find a better way
        p.print("");
        p.close();
        // Write into file
        p = new PrintWriter(new FileWriter("InputFile"));
        for(String row : output)
        {
            p.println(row);
        }



    } else {
        System.out.println("No records to process");
    }



    } catch(IOException e){
        e.printStackTrace();
    } finally { // Close file
        if(p!=null){
            p.close();
        }
        if(bufferedReader!=null){
            try {
                bufferedReader.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }
}

---

我强烈建议您了解什么是文件资源，如何有效地处理它们并改进此代码。稍后您应该转到Apache Commons库

这里是我的函数，用于计算到

private static int calculateTimeTill(int date) 
{
    // TODO Auto-generated method stub
    String numberAsString = Integer.toString(date);
    if(numberAsString.length() == 5)
    {
        //format 22017
        String month = numberAsString.substring(0,1);
        String year = numberAsString.substring(1,5);
        int monthResult = Integer.parseInt(month);
        int yearResult = Integer.parseInt(year);
        int day = 1;
        // using Joda - Time http://joda-time.sourceforge.net/installation.html
        // downloaded Joda - Convert as well
        LocalDate expDate = new LocalDate(yearResult, monthResult, day);
        LocalDate currDate = new LocalDate();
        int output = Months.monthsBetween(expDate, currDate).getMonths();
        return output;
    }
    else
    {
        //format 122017
        String month = numberAsString.substring(0,2);
        String year = numberAsString.substring(2,6);
        int monthResult = Integer.parseInt(month);
        int yearResult = Integer.parseInt(year);
        int day = 1;
        // using Joda - Time http://joda-time.sourceforge.net/installation.html
        // downloaded Joda - Convert as well
        LocalDate expDate = new LocalDate(yearResult, monthResult, day);
        LocalDate currDate = new LocalDate();
        int output = Months.monthsBetween(expDate, currDate).getMonths();
        return output;
    }
}

---

您是否愿意使用外部库，如apache commons csv和apache commons io？我希望代码尽可能简单，如果apache commons有助于做到这一点，并且可以方便地使用，我也愿意使用。没有apache commons，还有其他方法可以做到这一点吗？我找不到org.apache.commons.io.FileUtils.apache commons不是Java SDK的一部分。您可以将其用作外部Jar或使用Maven之类的构建工具—我获得了所有文件，并在抛出新的IllegalArgumentException时出错；ifelements.length==2检查是否正好有两个值由逗号分隔。您的输入csv文件正确吗？这是一个总体思路的示例，实际数据中有13列。基于什么？/您在哪里跳过行？如何确保它只从我的数据文件的第13列获取数据？我只是花了一些时间，写了一个单独的函数，从该列中获取输入，并输出一个时间，以月为单位，例如22017，当前日期和年份是22017，因此它将输出0，下个月发送int 22017，它将输出1。对于我来说，将计算到的时间与通过记录的时间分开会更容易。我已经在你的伪代码下添加了注释。无论如何，您可以替换iflength>0，String rec=entries[length-1]；iflength>12且字符串rec=条目[12]；我同意。计算时间的逻辑应该是一个独立的函数；LocalDate currDate=新的LocalDate；int output=Months.monthbetweenUpdate，currDate.getMonths；在if-else块之外调用该方法

PrintWriter f0 = new PrintWriter(new FileWriter("SomeFile",false));
        f0.print("");
        // Erase the contents of the input file in a
        // Very bad way
        f0.close();
        f0 = new PrintWriter(new FileWriter("output.txt"));
        for(String row : output)
        {
            f0.println(row);
        }
        f0.close();

    // read csv file
        // append timeTillExpired to end of first row of CSV
        // for each row after first row
            // calculate timeTillExpired
                // if format MYYYY (ex 22017)
                    // M and YYYY
                    // calculate relative to current date as months
                //else
                    // MM and YYYY (ex 122017)
                    // calculate relative to current date as months
            // if calculated > 3
                // timeTillExpired = ">3"
                // add timeTillExpired to end of row
            //else
                // add timeTillExpired to end of row
    // save file
    // close file

private void process(){
    BufferedReader bufferedReader = null;
    PrintWriter p = null;
    String sep = ",";
    String newCol = "monthsTill";
    String defaultTillExpMonth = ">3";
    Calendar cal = Calendar.getInstance();
    cal.setTime(new Date());
    int currMonth = cal.get(Calendar.MONTH) + 1;
    try {
    // read csv file
    List<String> input = new ArrayList<String>();
   File inputFile = new File("InputFile");
  bufferedReader = new BufferedReader(new FileReader(inputFile));
    String readLine = "";
    while ((readLine = bufferedReader.readLine()) != null) {
        input.add(readLine);
    }

 // for each row after first row
    // calculate timeTillExpired
        // if format MYYYY (ex 22017)
            // M and YYYY -> MM and YYYY

       // calculate relative to current date as months

    int numOfRecords = input.size();
    if(numOfRecords>1){
        List<String> output = new ArrayList<String>();
        String header = input.get(0) +sep +newCol;
        output.add(header);

        // for each row after first row
        // calculate timeTillExpired
        // if format MYYYY (ex 22017)
              // M and YYYY -> MM and YYYY
        // calculate relative to current date as months
        for(int i=1;i<numOfRecords;i++){
            // I am simply going to get the last column from record
            String row = input.get(i);
            StringBuilder res = new StringBuilder(row);
            String [] entries = row.split(sep);
            int length = entries.length;
            if(length>0){
                res.append(sep);
                String rec = entries[length-1];
                int expMonth = 0;
                // Case of MYYYY. Assumption is it's either MYYYY or MMYYYY
                if(rec.length()==5){
                    expMonth = Integer.valueOf(rec.substring(0, 1));
                } else {
                    expMonth = Integer.valueOf(rec.substring(0, 2));
                }

                int monToExp = expMonth - currMonth;
                // if calculated > 3
                if(monToExp > 3){
                    res.append(defaultTillExpMonth);
                } else {
                    res.append(monToExp);
                }
                output.add(res.toString());
            }
        }
        // Write into the same file.
        // First We'll delete everything in the input file and then write the modified records

        p = new PrintWriter(new FileWriter("output.txt",false));
        // Ouch. Very bad way to handle resources. You should find a better way
        p.print("");
        p.close();
        // Write into file
        p = new PrintWriter(new FileWriter("InputFile"));
        for(String row : output)
        {
            p.println(row);
        }



    } else {
        System.out.println("No records to process");
    }



    } catch(IOException e){
        e.printStackTrace();
    } finally { // Close file
        if(p!=null){
            p.close();
        }
        if(bufferedReader!=null){
            try {
                bufferedReader.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }
}

private static int calculateTimeTill(int date) 
{
    // TODO Auto-generated method stub
    String numberAsString = Integer.toString(date);
    if(numberAsString.length() == 5)
    {
        //format 22017
        String month = numberAsString.substring(0,1);
        String year = numberAsString.substring(1,5);
        int monthResult = Integer.parseInt(month);
        int yearResult = Integer.parseInt(year);
        int day = 1;
        // using Joda - Time http://joda-time.sourceforge.net/installation.html
        // downloaded Joda - Convert as well
        LocalDate expDate = new LocalDate(yearResult, monthResult, day);
        LocalDate currDate = new LocalDate();
        int output = Months.monthsBetween(expDate, currDate).getMonths();
        return output;
    }
    else
    {
        //format 122017
        String month = numberAsString.substring(0,2);
        String year = numberAsString.substring(2,6);
        int monthResult = Integer.parseInt(month);
        int yearResult = Integer.parseInt(year);
        int day = 1;
        // using Joda - Time http://joda-time.sourceforge.net/installation.html
        // downloaded Joda - Convert as well
        LocalDate expDate = new LocalDate(yearResult, monthResult, day);
        LocalDate currDate = new LocalDate();
        int output = Months.monthsBetween(expDate, currDate).getMonths();
        return output;
    }
}