java - 如何向 CSV 添加包含 Java 数据的列

Question

我们可以在 CSV 中添加一个新列作为最后一列吗？假设该列已经有 3 列，其中包含一些数据？因此，这个新列稍后将作为第四列添加，而且每一行都应该有随机数。

示例，

Id  Name   Address     Calculated
1   John    U.K.        341679
2   Vj      Aus         467123
3   Scott   U.S.        844257

据我了解，这需要首先读取 csv，for 循环可能是迭代到最后一列，然后添加一个新的计算列，即写入 csv。而添加值的可能是Java的Random类。但究竟如何才能做到这一点才是真正的问题。像示例代码会很有帮助。

代码:

import java.io.BufferedReader;
import java.io.FileReader;
import java.io.IOException;
import java.util.ArrayList;
import java.util.List;
import java.util.Random;


public class Demo1 {

    public static void main(String[] args) throws IOException {

        String csvFile = "C:\\MyData\\Input.csv";
        String line = "";
        String cvsSplitBy = ",";
        String newColumn = "";
        List<String> aobj = new ArrayList<String>();


  /* Code to read Csv file and split  */

        try (BufferedReader br = new BufferedReader(new FileReader(csvFile))) {


            while ((line = br.readLine()) != null)  
            {
                String[] csvData = line.split(cvsSplitBy);  
                int arrayLength = csvData.length;  


            }
        }


        /* Code to generate random number  */
        String CHARS = "1234567890";
        StringBuilder random = new StringBuilder();
        Random rnd = new Random();
        while (random.length() < 18) { // length of the random string.
            int index = (int) (rnd.nextFloat() * CHARS.length());
            random.append(CHARS.charAt(index));
        }
        String finaldata = random.toString();
    }
}

Answer 1

太好了，根据您提供的代码，这可能如下所示

(只是为了给你一个想法 - 我在没有测试的情况下即时写在这里......) :

import java.io.BufferedReader;
import java.io.FileReader;
import java.io.IOException;
import java.util.ArrayList;
import java.util.List;
import java.util.Random;


public class Demo1 {
    //moved your random generator here 
    public static String getRandomNumber() {
      /* Code to generate random number  */
        String CHARS = "1234567890";
        StringBuilder random = new StringBuilder();
        Random rnd = new Random();
        while (random.length() < 18) { // length of the random string.
            int index = (int) (rnd.nextFloat() * CHARS.length());
            random.append(CHARS.charAt(index));
        }
        String finaldata = random.toString();
        return finaldata;
     }

    public static void main(String[] args) throws IOException {

        String csvFile = "C:\\MyData\\Input.csv";
        String temporaryCsvFile = "C:\\MyData\\Output_temp.csv";
        String line = "";
        String cvsSplitBy = ",";
        String newColumn = "";
        List<String> aobj = new ArrayList<String>();


  /* Code to read Csv file and split  */

        BufferedWriter writer = new BufferedWriter(new FileWriter(
                temporaryCsvFile));


        try (BufferedReader br = new BufferedReader(new FileReader(csvFile))) {


            while ((line = br.readLine()) != null)  
            {
                //String[] csvData = line.split(cvsSplitBy);  
                //int arrayLength = csvData.length;  
                //actually you don't even need to split anything 
                 String newFileLine = line + cvsSplitBy  + getRandomNumber();  
                 // ... We call newLine to insert a newline character.
                  writer.write(newFileLine);
                  writer.newLine();

            }
        }
              writer.close();
              //Now delete the old file and rename the new file
              //I'll leave this to you 


    }
}