尝试访问列 Java CSV 时出现问题

Question

我有问题，我正在尝试从 JAVA 中的 CSV 存档访问列。我编写了一个函数，即 return 来自 csv 存档的所有数据。但我想根据条件 return 1 列。条件是，列区域。

如果区域编号为1，则结果为，例如SQL。

SELECT region, sum(nviv) AS 'HOUSES' FROM census WHERE region = 1

子句returns 1 区域 1 的值，所有列 nviv 的总和。我尝试这样做，但在 JAVA 和 OpenCSV 中。

这是我的代码，我是 java 使用 CSV 存档编程的新手。

package hogares;

import java.util.*;
import com.opencsv.*;
import java.io.*;

public class Hogares {

    public static final String SEPARADOR = ";";

    public static void main(String[] args){

        int opc;
        Scanner sc = new Scanner(System.in);

        System.out.println("MENU HOMES");
        System.out.println("");

        System.out.println("1. Count Regions by region number");
        System.out.println("2. Average of homes of blocks by region number");
        System.out.println("3. Blocks number by region number");
        System.out.println("4. Exit");
        System.out.println("");

        System.out.println("Select an option: ");
        opc = sc.nextInt();

        switch(opc){
            case 1:
                CountHome();
                break;
            case 2:
                AverageHome();
                break;
            case 3:
                BlocksNumber();
                break;
            case 4:
                System.out.println("EXITING...");
                System.out.println("");
                break;
            default:
                System.out.println("Invalid option...");
                break;
        }
    }

    private static void CountHome(){

        int region;
        Scanner lee = new Scanner(System.in);

        BufferedReader csvr = null;
        try {


            csvr = new BufferedReader(new FileReader("C:\Users\ADMIN\Desktop\census2010.csv"));

            String[] headers = new String[]{"REGION","PROVINCE","COMMUNE","DC","AREA","ZC_LOC","ID_ZONE_LOC","NVIV","NHOME","TIPE_HOME","TIPE_OPERATIVE"};

            System.out.println("Tell me a number: ");
            region = lee.nextInt();


            String line = csvr.readLine();
            while (null!=line) {
                headers = line.split(SEPARADOR);
                System.out.println(Arrays.toString(headers));


                System.out.println(Arrays.toString(headers));

                line = csvr.readLine();
            }
        }
        catch (IOException e) {
            e.printStackTrace();
        }
        finally{

            if (csvr != null) {
                try {
                    csvr.close();
                }
                catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }

    }

    private static void AverageHome() {

    }

    private static void BlocksNumber() {

    }
}

这是输出。请记住，我正在尝试 return 1 个结果，具体取决于此行中的数字：

System.out.println("Tell me a number: ");
region = lee.nextInt();

Answer 1

添加了代码注释以进行解释

    private static void CountHome() {

        int requestedRegion;
        Scanner scanner = new Scanner(System.in);

        System.out.println("Tell me a number: ");
        requestedRegion = scanner.nextInt();

        try {
            FileReader filereader = new FileReader("C:\\Users\\ADMIN\\Desktop\\census2010.csv");

            // Use OpenCsv to read CSV file
            CSVReader csvReader = new CSVReader(filereader);

            System.out.println("REGION\tHOUSES");

            //Assign it to skip header row from records
            String[] nextLine = csvReader.readNext();

            //Take variable to for sum of nviv
            int houses = 0;

            // Read CSV record one by one
            while ((nextLine = csvReader.readNext()) != null) {

                // Get first column value which is region
                String region = nextLine[0];

                // Get nviv column value
                String nviv = nextLine[7];

                // Check region and nviv is not null and empty
                if (region != null && !region.isEmpty() && nviv != null && !region.isEmpty()) {

                    // Parse region string to integer
                    int currentRegion = Integer.parseInt(region);

                    // Check row region is equals to region entered by user
                    if (currentRegion == requestedRegion) {

                        // Parse nviv sting to integer
                        int currentNviv = Integer.parseInt(nviv);

                        // Sum nviv And get total houses
                        houses = houses + currentNviv;

                        // System.out.println(region + "\t" + nviv);
                    }
                } else {
                    System.out.println("Invalid data to proceed");
                }
            }
            System.out.println(requestedRegion + "\t" + houses);

        } catch (Exception e) {
            e.printStackTrace();
        }
    }

示例 CSV 数据：

REGION,PROVINCE,COMMUNE,DC,AREA,ZC_LOC,ID_ZONE_LOC,NVIV,NHOME,TIPE_HOME,TIPE_OPERATIVE
1,2,33,4,5,66,7,8,9,10,11
2,2,33,4,5,66,7,8,9,10,11
1,2,33,4,5,66,7,8,9,10,11
2,2,33,4,5,66,7,8,9,10,11
1,2,33,4,5,66,7,8,9,10,11
1,2,33,4,5,66,7,8,9,10,11
7,2,33,4,5,66,7,8,9,10,11
7,2,33,4,5,66,7,8,9,10,11
7,2,33,4,5,66,7,8,9,10,11
7,2,33,4,5,66,7,8,9,10,11
7,2,33,4,5,66,7,8,9,10,11
8,2,33,4,5,66,7,8,9,10,11
8,2,33,4,5,66,7,8,9,10,11
8,2,33,4,5,66,7,8,9,10,11
8,2,33,4,5,66,7,8,9,10,11
8,2,33,4,5,66,7,8,9,10,11

输出：

MENU HOMES

1. Count Regions by region number
2. Average of homes of blocks by region number
3. Blocks number by region number
4. Exit

Select an option: 
1
Tell me a number: 
7
REGION  HOUSES
7   40

如果 CSV 有空行，结果可能会出错，

检查是否存在任何空行，如果找到则跳过

           // Read CSV record one by one
            while ((nextLine = csvReader.readNext()) != null) {

                // Check row empty, if found skip iteration
                if (nextLine.length != 0 && nextLine[0].trim().isEmpty()) {
                    continue;
                }

尝试访问列 Java CSV 时出现问题

Problem whit trying to access to a column Java CSV

java

opencsv