Java - Storing numbers from input file in a 2D array

Question

My goal of this program is to take numbers from an input text file, called seatPrices.txt and save them in an array of type double, called priceArray .

The input file is:

310:300:320:320:300:310
360:350:370:370:350:360
360:350:370:370:350:360
360:350:370:370:350:360
360:350:370:370:350:360
260:250:270:270:250:260
260:250:270:270:250:260
260:250:270:270:250:260
260:250:270:270:250:260
260:250:270:270:250:260
210:200:220:220:200:210
210:200:220:220:200:210
210:200:220:220:200:210
210:200:220:220:200:210
210:200:220:220:200:210
210:200:220:220:200:210
210:200:220:220:200:210
210:200:220:220:200:210
210:200:220:220:200:210
210:200:220:220:200:210
110:100:120:120:100:110
110:100:120:120:100:110
110:100:120:120:100:110
110:100:120:120:100:110
110:100:120:120:100:110
110:100:120:120:100:110
110:100:120:120:100:110
110:100:120:120:100:110
110:100:120:120:100:110
110:100:120:120:100:110

My code for this is:

import java.io.FileReader;
import java.util.Scanner;
import java.io.IOException;

public class testAirline {

    // initializing variables and arrays
    private static final int MAX_COLUMN = 6;
    private static final int MAX_ROW = 30;
    double[][] priceArray;
    FileReader fr;
    Scanner scan;

    // this constructor reserves memory for arrays and sets the filereader and scanner variables, then call "start" method
    public void Airline() throws IOException {      
        priceArray = new double[MAX_ROW][MAX_COLUMN];
        fr = new FileReader(seatPrices);
        scan = new Scanner(fr).useDelimiter(":");
        start();
    }

    // fills the priceArray with numbers from seatPrices.txt
    private void start() {
        for (int i = 0; i < MAX_ROW; i++) {
            for (int j = 0; j <  MAX_COLUMN; j++) {
                priceArray[i][j] = scan.nextDouble();
            }
        }
    }
}

When I run this, I get the following errors in the console:

Exception in thread "main" java.util.InputMismatchException
    at java.util.Scanner.throwFor(Scanner.java:864)
    at java.util.Scanner.next(Scanner.java:1485)
    at java.util.Scanner.nextDouble(Scanner.java:2413)
    at testAirline.start(Airline.java:19)
    at testAirline.Airline(Airline.java:12)

So the errors appear to come from when I call the "start" method ( start() ) and when the numbers are scanned from the file to be stored in the array. I do not know why these errors are being thrown. Being that I am new to using delimiter , I thought these problems could have stemmed from not formatting it properly, however this suspicious was squashed when I found what lines in my code the errors were being thrown at.

I was not able to find an answer on here that worked in my program. I am open to all possible solutions! Any and all help is appreciated!

Edit:

Output from @robert's suggested code:

:0,0 : 310.0
:0,1 : 300.0
:0,2 : 320.0
:0,3 : 320.0
:0,4 : 300.0
:1,0 : 360.0
:1,1 : 350.0
:1,2 : 370.0
:1,3 : 370.0
:1,4 : 350.0
:2,0 : 360.0
:2,1 : 350.0
:2,2 : 370.0
:2,3 : 370.0
:2,4 : 350.0
:3,0 : 360.0
:3,1 : 350.0
:3,2 : 370.0
:3,3 : 370.0
:3,4 : 350.0
:4,0 : 360.0
:4,1 : 350.0
:4,2 : 370.0
:4,3 : 370.0
:4,4 : 350.0
:5,0 : 260.0
:5,1 : 250.0
:5,2 : 270.0
:5,3 : 270.0
:5,4 : 250.0
:6,0 : 260.0
:6,1 : 250.0
:6,2 : 270.0
:6,3 : 270.0
:6,4 : 250.0
:7,0 : 260.0
:7,1 : 250.0
:7,2 : 270.0
:7,3 : 270.0
:7,4 : 250.0
:8,0 : 260.0
:8,1 : 250.0
:8,2 : 270.0
:8,3 : 270.0
:8,4 : 250.0
:9,0 : 260.0
:9,1 : 250.0
:9,2 : 270.0
:9,3 : 270.0
:9,4 : 250.0
:10,0 : 210.0
:10,1 : 200.0
:10,2 : 220.0
:10,3 : 220.0
:10,4 : 200.0
:11,0 : 210.0
:11,1 : 200.0
:11,2 : 220.0
:11,3 : 220.0
:11,4 : 200.0
:12,0 : 210.0
:12,1 : 200.0
:12,2 : 220.0
:12,3 : 220.0
:12,4 : 200.0
:13,0 : 210.0
:13,1 : 200.0
:13,2 : 220.0
:13,3 : 220.0
:13,4 : 200.0
:14,0 : 210.0
:14,1 : 200.0
:14,2 : 220.0
:14,3 : 220.0
:14,4 : 200.0
:15,0 : 210.0
:15,1 : 200.0
:15,2 : 220.0
:15,3 : 220.0
:15,4 : 200.0
:16,0 : 210.0
:16,1 : 200.0
:16,2 : 220.0
:16,3 : 220.0
:16,4 : 200.0
:17,0 : 210.0
:17,1 : 200.0
:17,2 : 220.0
:17,3 : 220.0
:17,4 : 200.0
:18,0 : 210.0
:18,1 : 200.0
:18,2 : 220.0
:18,3 : 220.0
:18,4 : 200.0
:19,0 : 210.0
:19,1 : 200.0
:19,2 : 220.0
:19,3 : 220.0
:19,4 : 200.0
:20,0 : 110.0
:20,1 : 100.0
:20,2 : 120.0
:20,3 : 120.0
:20,4 : 100.0
:21,0 : 110.0
:21,1 : 100.0
:21,2 : 120.0
:21,3 : 120.0
:21,4 : 100.0
:22,0 : 110.0
:22,1 : 100.0
:22,2 : 120.0
:22,3 : 120.0
:22,4 : 100.0
:23,0 : 110.0
:23,1 : 100.0
:23,2 : 120.0
:23,3 : 120.0
:23,4 : 100.0
:24,0 : 110.0
:24,1 : 100.0
:24,2 : 120.0
:24,3 : 120.0
:24,4 : 100.0
:25,0 : 110.0
:25,1 : 100.0
:25,2 : 120.0
:25,3 : 120.0
:25,4 : 100.0
:26,0 : 110.0
:26,1 : 100.0
:26,2 : 120.0
:26,3 : 120.0
:26,4 : 100.0
:27,0 : 110.0
:27,1 : 100.0
:27,2 : 120.0
:27,3 : 120.0
:27,4 : 100.0
:28,0 : 110.0
:28,1 : 100.0
:28,2 : 120.0
:28,3 : 120.0
:28,4 : 100.0
:29,0 : 110.0
:29,1 : 100.0
:29,2 : 120.0
:29,3 : 120.0
:29,4 : 100.0

Answer 1

public class InputMismatchException extends NoSuchElementException Thrown by a Scanner to indicate that the token retrieved does not match the pattern for the expected type, or that the token is out of range for the expected type.

priceArray[i][j] = Double.parseDouble(scan.next());

Answer 2

You could assist with your hunt for the flaw by adding some more informative error output eg

private void start() {
    for (int i = 0; i < MAX_ROW; i++) {
        for (int j = 0; j <  MAX_COLUMN; j++) {
            try {
                priceArray[i][j] = scan.nextDouble();
            } catch (Exception e) {
                System.err.println("Error discovered at " + i + "," + j ": " + e);
            }
        }
    }
}

This will at least tell you what line/column your input was bad on.

You'll see errors like this:

Error discovered at 0,5: java.util.InputMismatchException

which should indicate to you that the scanner is going beyond the end of the line. You need to guard your call to nextDouble() :

                if (scan.hasNextDouble()) {
                    priceArray[i][j] = scan.nextDouble();
                    System.out.println(":" + i + "," + j + " : " + priceArray[i][j]);
                }

You'll also need to advance to the next line for each row:

        if (scan.hasNextLine()) {
            scan.nextLine();
        }

The following revised start() function should correctly parse your input:

// fills the priceArray with numbers from seatPrices.txt
private void start() {
    for (int i = 0; i < MAX_ROW; i++) {
        for (int j = 0; j <  MAX_COLUMN; j++) {
            try {
                if (scan.hasNextDouble()) {
                    priceArray[i][j] = scan.nextDouble();
                    System.out.println(":" + i + "," + j + " : " + priceArray[i][j]);
                }
            } catch (Exception e) {
                System.err.println("Error discovered at " + i + "," + j + ": " + e);
            }
        }
        if (scan.hasNextLine()) {
            scan.nextLine();
        }
    }
}

Answer 3

If you check the java docs for the Scanner class, it says that,

The method nextDouble() will throw InputMismatchException if the next token cannot be translated into a valid double value. If the translation is successful, the scanner advances past the input that matched.

Although, in your code you have set the delimiter to : , the code breaks when new line .ie \\n is encountered. Hence, to make your code to store the data in 2D matrix of type double , try changing your scanner to:

Scanner sc = new Scanner(new FileInputStream(new File(pathOfInpFile));

and change your for loops in start() method to:

for(int row = 0; row < rowcount; row++){
                //Read each line. No. of lines will be equal to the no. of rows in file.
                String eachLine = sc.nextLine();
                /*
                 * Split each line at ':'. This gives you a String array of 
                 * length equal to no. of columns in file.
                 */
                String[] columnData = eachLine.split(":");
                for(int col = 0; col < colCount; col++){
                    //Now, store data in your matrix.
                    data[row][col] = Double.parseDouble(columnData[col]);
                }
            }

I hope this solves your problem.