Thread: Loading an array from a .txt file

First post I am making here and hopefully it will be a good one.

I have the following code:

// File:  Array07.java
 
/*  *********************************************
    The program creates a file based on the random values
    generated for an array..
 
	********************************************* */
import java.util.Scanner;
import java.io.*;
 
public class Array07
{
 
    public static void main(String[ ] args)
	    throws java.io.IOException
	{
 
		String endMsg = "***** end of Array07 *****";
 
		FileReader arrayIn = new FileReader("Array07Data.txt");
		int [] [] array07 = new int [7] [8];
		int i = 0;
		int j = 0;
		Scanner inData = new Scanner(arrayIn);
/*
		[B]Develop the code to load the array
		from the file Array07.txt. In order for the for loop
		below to work properly, the code to fill the array
		should be placed here...[/B]*/
 
		for(i = 0; i < array07.length; i++) {
			for(j = 0; j < array07[i].length; j++) {
				System.out.printf("%5d",array07[i] [j]);
			}
			System.out.println();
		}
		arrayIn.close();
		System.out.println(endMsg);
    } // end of method main
 
} // end of Array07 class

I have highlighted in bold what I am asked to do. I am supposed to load the array in the file "Array07Data.txt". The "Array07Data.txt" contains the following array:

1422
927
259
400
1170
356
1193
876
114
1454
286
1237
1406
237
32
577
921
1407
692
656
1002
365
1191
1136
1382
196
783
1454
712
607
243
1113
185
1438
174
385
258
1002
593
727
1483
1386
782
626
973
173
945
633
986
657
993
479
84
673
781
914

How do I load this into the program? Running the program as it is, it just gives me an array of zeros. It's probably simple stuff but to me it isn't.

Where does the code assign any values to the array?

Originally Posted by NEPALII

How do I load this into the program? Running the program as it is, it just gives me an array of zeros.

Just only
Scanner inData = new Scanner(arrayIn);

does not read any file content. You have to read each number token using (presumably, being int values) nextInt() of Scanner, and assign these values to array elements.

Originally Posted by NEPALII

So I have to put Scanner nextInt() in order to read file content? I'm confused.

The main purpose of Scanner is to read "tokens", by default separated by any number of "whitespaces" (also end-of-lines). In your file you have many integer tokens. Thus, you have to invoke many times nextInt() to read each single integer token.

In your initial code, the double-for loop to print the array is correct. Do a similar double-for loop to read integers and assign them into the array.

Originally Posted by NEPALII

I have no clue on how to get a loop to read integers and assign them into the array. That double for loop, like you said, prints out the array into the program, right?

Yes, the double-for loop you have already written is correct but prints only the content of the matrix.
It would be possible to read each integer into that loop, just before the System.out.printf. But the matrix would be useless (you read and print immediately a value, where is the meaning of the matrix?).

So before that double-loop, make a pratically equal loop, with one difference: instead to print, invoke nextInt() on the Scanner and assign the return value to the array element at the row/column i,j.


P.S. It's better to close the Scanner ... not the FileReader.

Originally Posted by NEPALII

Something like this?

Scanner int x = x.next.Int();
Scanner int Array07Data = Array07Data.next.Int();

No, both are wrong (for syntax and meaning).

This reads 1 integer token (where inData is the reference to your Scanner instance):

int value = inData.nextInt();

While the following fills an int[] (monodimensional):

int[] arr = new int[10];
 
for (int i = 0; i < arr.length; i++) {
    arr[i] = inData.nextInt();
}

Your case is slightly different: you have a bidimensional array. Thus, do a double-for loop and into this loop read the integer token and assign the value to the array element at row/column i,j.

@micronome Please don't spoonfeed code.
See: http://www.javaprogrammingforums.com...n-feeding.html