Data Type for a CSV File processing problem

[James Joe]

Hi,

I am breaking my head on this problem to find a suitable data type to use, but I am not able to settle with which one would be the most efficient and simple way to program this without using any third party libraries:

Problem:
Consider Share prices for a N number of companies given for each month since year 1990 in a CSV file. Format of the file is as below with first line as header.

Year,Month,Company A, Company B,Company C, .............Company N
1990, Jan, 10, 15, 20, , ..........,50
1990, Feb, 10, 15, 20, , ..........,50
.
.
.
.
2013, Sep, 50, 10, 15............500

Output:
List for each Company year and month in which the share price was highest.

I've considered using trees, Hashmap, Lists but I am unable to finalise THE ONE solution. I am a newbie to Java with a couple of weeks of Java coding experience so far. Any help in the form of pseudo code, program or what data type to use is appreciated.

[Campbell Ritchie]

Welcome to the Ranch

We have an FAQ about different file types; that might help you. Try under “Excel”.

[Campbell Ritchie]

I suggest you need a Company class or a SharePriceHistory class.

[James Joe]

Thank you Campbell Ritchie. But the constraint here is that the CSV parsing has to be done without using third party libraries.
I have the following so far, but I think I am not heading the right way. The csv parsing is turning out to be very messy and complicated:

Any suggestion with the CSV parsing to fit the solution? I have reached a dead end!

package com.trade;

import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.util.HashMap;
import java.util.Map;
import java.util.Scanner;

public class Company {

	private String name;
	private String year;
	private String month;
	private double price;
	
	private static String[] header;
	private static int lineCount = 0;
	private static int rows = 0;
	private static int columns = 0;

	public Company(String name, String year, String month, double price) {
		this.name = name;  
		this.year = year; 
		this.month = month; 
		this.price = price;
	}

	public String getName() {
		return name;
	}

	public void setName(String name) {
		this.name = name;
	}

	public String getYear() {
		return year;
	}

	public void setYear(String year) {
		this.year = year;
	}

	public String getMonth() {
		return month;
	}

	public void setMonth(String month) {
		this.month = month;
	}

	public double getPrice() {
		return price;
	}

	public void setPrice(double price) {
		this.price = price;
	}
	
	// Simply read the CSV and return the next set of company data
	private static Company getNextCompanyData(Scanner scanner) {
		
		String name = "ABC"; // get company name from CSV file
		String year = "1992"; // get year data from CSV file
		String month = "Feb"; // get month data from CSV file
		double price = 88.2;  // get price data from CSV file
		return new Company(name, year, month, price);
	}

	public static void main(String[] args) {
		
		if (0 >= args.length) {
		   System.err.println("Invalid arguments count: " + args.length);
		   System.exit(1);
		}
		
		Scanner scanner = readFile(args[0]);
		countRowsColumnsStoreHeader(scanner);
		
		String[][] yearMonths = new String[lineCount-1][2];
		String[][] sharePrices = new String[lineCount-1][columns-2];
		
		Scanner scanData = readFile(args[0]);
		populateData(scanData, yearMonths, sharePrices);
        
		Map<String, Company> companies = new HashMap<String,Company>();
		Company newCompany = null;

		// repeat until all company data processed from CSV file
		while ((newCompany = getNextCompanyData(scanner)) != null) {
			Company oldCompany = companies.get(newCompany.getName());
			if (oldCompany == null || newCompany.getPrice() > oldCompany.getPrice()) 
				companies.put(newCompany.getName(), newCompany);
		}
		// Done, now display the winners
		for (String name : companies.keySet()) {
			Company company = companies.get(name);
			System.out.println(company.getName() + " highest price " + company.getPrice() + 
					" is " + company.getMonth() + " " + company.getYear());
		}
	}
	
	private static void populateData(Scanner scanData, String[][] yearMonths, String[][] sharePrices) {
		int rowCount = 0;
		if (rowCount == 0 && scanData.hasNextLine()){
			scanData.nextLine();
		}
	
		while (scanData.hasNextLine())
		{
			String[] record = (scanData.nextLine()).split(",");
			//run nested for loops to populate 2 dimensional array with data 
		}
	}

	private static void countRowsColumnsStoreHeader(Scanner scanner) {
        if (lineCount == 0){
        	if(scanner.hasNextLine()){
            String firstLine = scanner.nextLine();
            header = firstLine.split(",");
            columns = header.length;
            lineCount++;
        	}
        }
        while (scanner.hasNextLine()){
        	scanner.nextLine();
        	lineCount++;
        }
        scanner.close();
	}

	private static Scanner readFile(String inFile){
		//Scanner Example - read file line by line in Java using Scanner
        FileInputStream fis = null;
		try {
			fis = new FileInputStream(inFile);
		} catch (FileNotFoundException e) {
			System.err.println("File "+inFile+" not found.");
			e.printStackTrace();
			System.exit(1);
		}
		
        Scanner scanner = new Scanner(fis);
        
        return scanner;
        /*//reading file line by line using Scanner in Java
        System.out.println("Reading file line by line");
*/      
	}
}

[Ulf Dittmer]

I'd say partly that's a reflection that CSV is not quite as trivial as it first looks, and partly a reflection that the contents of the file you're dealing with have a structured format, i.e. not entirely trivial, either.

One thing I would do differently is using collections instead of arrays, so that I wouldn't have to worry about array sizes.

But the constraint here is that the CSV parsing has to be done without using third party libraries.

Why is that? The parser doesn't implement all CSV features yet, so it's going to get more complicated - something an open source 3rd party library can help avoid safely.