reading a string, int, and double from csv file

Question

Hello everyone i am trying to read a string, an int and a double from a csv file. This is a sample from my csv file:

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.

I am required to read the string into an array called String[] countryNames , read the years and store it into an int[] yearLabels and finally the double double[][] cellularDataTable .

I created a function for each array called public String[] getCountryNames() , public int[] getYearLabel() , and public data[][] getCellularDataTable() . I created my class called Class CSVReader and those methods are in my class. In the String array function i am meant to skip the first line of the class and read the line Number of countries,252 and store 252 for the size of the array of the string and return it or store each country into the string array. My algorithm is wrong and would need some guidance. The year function is only meant to read the years, so basically get the row of country and store in the years, and the double[][] function reads the country and the stats. Because i will be passing the arrays into my TestClass such as:

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

Below is my CSVReader class file:

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()
{

}
}

If some can can give me example of how to store the strings, int and double i believe i can understand. I think i have my idea down just don't know how to implement the code. Will appreciate the help and i am new to programming. Thanks

Answer 1

From a design standpoint, you should be doing the file reading once and storing the data so you can later access it quickly. There's no reason to separate the parsing out into many locations; just do the parsing all at once and store it where it should go.

Using your current paradigm, you should be doing all of your file reading in the constructor, so that as soon as you start using the object you've constructed all of the data is already read in.

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;
    }
}