java - 从 csv 文件读取字符串、int 和 double

Question

大家好，我正在尝试从 csv 文件中读取字符串、int 和 double。这是我的 csv 文件中的示例:

World Development Indicators
Number of countries,252
CountryName,1960,1961,1962,1963,1964,1965,1966,1967,1968,1969,1970,1971,1972,1973,1974,1975,1976,1977,1978,1979,1980,1981,1982,1983,1984,1985,1986,1987,1988,1989,1990,1991,1992,1993,1994,1995,1996,1997,1998,1999,2000,2001,2002,2003,2004,2005,2006,2007,2008,2009,2010,2011,2012
Aruba,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0.029310471,0,0,2.138784453,3.605985937,3.98141538,6.16435217,13.48254011,16.50927821,57.05427692,65.05605558,72.10431377,99.64250268,103.3849507,108.1325002,112.2180618,119.2038996,126.2103374,129.72824,0,131.8565401
Andorra,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,1.307211734,1.278625641,1.250259142,4.424155104,8.538444783,13.44671556,22.12730607,32.14530928,35.99902139,43.27794118,45.77115817,68.60251444,73.82494308,79.48487497,84.27763597,78.1171579,80.2836099,82.06181111,84.06818386,83.53432222,81.50204186
Afghanistan,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0.112598381,0.865196277,2.498055472,4.826865367,9.833164022,17.71624331,29.22037376,37.89493697,45.77817474,60.32631999,60.35299258.

我需要将字符串读入名为String[]countryNames的数组，读取年份并将其存储到int[]yearLabels中，最后将双double[][]cellularDataTable.

我为每个数组创建了一个函数，名为 public String[] getCountryNames()、public int[] getYearLabel() 和 public data[][ ] getCellularDataTable()。我创建了名为 Class CSVReader 的类，这些方法位于我的类中。在字符串数组函数中，我打算跳过类的第一行并读取行 Number of states,252 并存储 252 作为字符串数组的大小，然后返回它或存储每个将国家/地区放入字符串数组中。我的算法是错误的，需要一些指导。 Year 函数仅用于读取年份，因此基本上获取国家/地区行并将其存储在年份中，而 double[][] 函数则读取国家/地区和统计数据。因为我将把数组传递到我的 TestClass 中，例如:

 CSVReader parser = new CSVReader(FILENAME);
 String [] countryNames = parser.getCountryNames();
 int [] yearLabels = parser.getYearLabels();
 double [][] parsedTable = parser.getCellularDataTable();

下面是我的 CSVReader 类文件:

import java.io.*;
import java.util.Scanner;

public class CSVReader {
String[] countryNames;
int[] yearNum;
double[][] tables;
Scanner scan;

public CSVReader(String filename)// throws FileNotFoundException 
{ 
    File file = new File(filename);
    try
    {
        scan = new Scanner(file);
    }
    catch(FileNotFoundException e)
    {
        System.out.println(e.getMessage());
    }

}

public String[] getCountryNames()
{
    scan.nextLine();
    while(scan.hasNext())
    {
        final String input = scan.nextLine();
        String[] country = input.split(",");
        //int a = Integer.parseInt(countryNames[1]);
        System.out.println(country[0]);
        int numberOfCountries = Integer.parseInt(country[1]);
    }
    scan.close();
}
public int[] getYearLabels()
{

}
public double[][] getParsedTable()
{

}
}

如果有人可以给我如何存储字符串、int 和 double 的例子，我相信我能理解。我想我已经有了我的想法，只是不知道如何实现代码。将感谢您的帮助，我是编程新手。谢谢

Answer 1

从设计的角度来看，您应该读取一次文件并存储数据，以便以后可以快速访问它。没有理由将解析分离到多个位置；只需立即进行所有解析并将其存储在应该存放的位置即可。

使用当前的范例，您应该在构造函数中读取所有文件，这样一旦您开始使用您构造的对象，所有数据都已被读入。

import java.io.*;
import java.util.Scanner;

public class CSVReader {
    String[] countryNames;
    int[] yearNum;
    double[][] tables;

    public CSVReader(String filename) throws FileNotFoundException{ 
        File file = new File(filename);
        Scanner scan = new Scanner(file);
        scan.nextLine(); //Skip the header line

        //Read the int on the next line to allocate arrays
        String numLine = scan.nextLine();
        final int n = Integer.parseInt(numLine.split(",")[1]); //Number is the string portion after the first comma

        //Allocate arrays with length n
        countryNames = new String[n];
        tables = new double[n][];

        //Read in the header line of years, parse and copy into yearNum
        String[] yearHeaders = scan.nextLine().split(",");
        final int m = yearHeaders.length - 1;
        yearNum = new int[m];
        for(int i = 0; i < m; i++){
            yearNum[i] = Integer.parseInt(yearHeaders[i+1]); //i+1 to skip the first entry in the string arr
        }

        //Now read until we run out of lines - put the first in country names and the rest in the table
        int c = 0;
        while(scan.hasNext()){
            String[] inputArr = scan.nextLine().split(",");
            countryNames[c] = inputArr[0];
            tables[c] = new double[m];
            for(int i = 0; i < m; i++){
                tables[c][i] = Double.parseDouble(inputArr[i+1]);
            }
            c++;
        }
        scan.close();
    }

    public String[] getCountryNames(){
        return countryNames;
    }
    public int[] getYearLabels(){
        return yearNum;
    }
    public double[][] getParsedTable(){
        return tables;
    }
}