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文件中的一个示例：

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的数组中，读取年份并将其存储到int[] yearLabels中，最后将其存储为double[][] cellularDataTable。

我为每个名为public String[] getCountryNames()，public int[] getYearLabel()和public data[][] getCellularDataTable()的数组创建了一个函数。我创建了一个名为Class CSVReader的类，这些方法都在我的班级中。在String数组函数中，我想跳过类的第一行并读取行Number of countries,252并存储252作为字符串数组的大小并返回它或将每个国家存储到字符串数组中。我的算法错了，需要一些指导。年份函数仅用于读取年份，因此基本上可以获取年份中的国家和商店行，而double [] []函数读取国家和统计数据。因为我将数组传递给我的TestClass，如：

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

以下是我的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()
{

}
}

如果有人可以给我一些如何存储字符串的例子，int和double我相信我能理解。我想我的想法只是不知道如何实现代码。将欣赏帮助，我是编程新手。感谢

Answer 1

从设计的角度来看，您应该进行一次文件读取并存储数据，以便以后快速访问。没有理由将解析分成许多位置;只需一次完成解析并将其存储在应该去的地方。

使用您当前的范例，您应该在构造函数中执行所有文件读取，这样一旦您开始使用您构建的对象，就已经读入了所有数据。

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;
    }
}

从csv文件中读取字符串，int和double

1 个答案: