3 dimensional array index out of bounds

Question

This is my first question here. I am trying to write a program that reads as many arrays as I input from the keyboard. After inputting the number of columns I get the error: Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: 0

Thanks in advance.

package Final;

import java.util.*;

public class Final {
    int a,b,x,l;
    double mat[][][];

    Final()
    {
        a=0;
        b=0;
        c=0;
        d=0;
        x=0;
        l=0;
    }

    public void read() {
        Scanner citast = new Scanner(System.in);
        System.out.println("How many arrays do you want to enter?");
        x=citast.nextInt();
        for (this.l=0; this.l<x; this.l++)
        {
              System.out.println("Matrix "+this.l);
              System.out.println("Number of lines: ");
              this.a = citast.nextInt();
              System.out.println("Number of columns: ");
              this.b = citast.nextInt();
              this.mat= new double [this.l][a][b];
              for (int i=0; i<this.a; i++)
               {
                  for (int j=0; j<this.b; j++)
                   {
                      System.out.print("Matrice " + l + " ["+ i +"]["+ j +"]= ");
                      this.mat[l][i][j]=citast.nextInt();
                   }
                  System.out.println();
            }
        }
    }

    public static void main(String[] args) {
        Final a = new Final();
        Scanner citast = new Scanner(System.in);
        a.read();
        System.out.println();

}

}

What is the point of having Scanner citast = new Scanner(System.in); in main? — inixsoftware
– inixsoftware, Commented Nov 24, 2013 at 15:05
try to give meaningful variables names like rows height columnsIterator... — iShaalan
– iShaalan, Commented Nov 24, 2013 at 15:08
Do you really want to allow differently sized matrices for each l? — Ridcully
– Ridcully, Commented Nov 24, 2013 at 15:10
@inixsoftware The code was edited here, I have more functions in the program and I forgot to remove the Scanner. — Sebastian N.
– Sebastian N., Commented Nov 24, 2013 at 15:38

Alexis C. · Accepted Answer · 2013-11-24 15:15:48Z

this.mat= new double [this.l][a][b];

Should be:

this.mat= new double [x][a][b];

But your code is wrong, you should set the dimension of the array before the first for loop :

public void read() {
        Scanner citast = new Scanner(System.in);
        System.out.println("How many arrays do you want to enter?");
        x=citast.nextInt();
        this.mat = new double[x][][]; //<-- added this line
        for (this.l=0; this.l<x; this.l++)
        {
            System.out.println("Matrix "+this.l);
            System.out.println("Number of lines: ");
            this.a = citast.nextInt();
            System.out.println("Number of columns: ");
            this.b = citast.nextInt();
            this.mat[l] =  new double [a][b]; //<-- modified this line
            for (int i=0; i<this.a; i++)
                for (int j=0; j<this.b; j++)
                {
                    System.out.print("Matrice " + l + " ["+ i +"]["+ j +"]= ");
                    this.mat[l][i][j]=citast.nextInt();
                }
            System.out.println();
        }
        System.out.println(Arrays.deepToString(mat));
    }

Output for an array containing 2 square matrices (one filled with 4 and one with 5):

[[[4.0, 4.0], [4.0, 4.0]], [[5.0, 5.0], [5.0, 5.0]]]

Ridcully · Accepted Answer · 2013-11-24 15:15:46Z

This should work. At first you create an array of size x to hold arbitrary sized two-dimensional arrays. Then for each l you create a two-dimensional array of size a x b, put it at position l of mat and read the values into it.

Scanner citast = new Scanner(System.in);
System.out.println("How many arrays do you want to enter?");
x=citast.nextInt();

this.mat = new double[x][][];

for (this.l=0; this.l<x; this.l++) {
    System.out.println("Matrix "+this.l);
    System.out.println("Number of lines: ");
    this.a = citast.nextInt();
    System.out.println("Number of columns: ");
    this.b = citast.nextInt();
    this.mat[this.l] = new double [a][b];
    for (int i=0; i<this.a; i++)
        for (int j=0; j<this.b; j++)
        {
            System.out.print("Matrice " + l + " ["+ i +"]["+ j +"]= ");
            this.mat[l][i][j]=citast.nextInt();
        }
        System.out.println();
    }
}

WonderWorld · Accepted Answer · 2013-11-24 15:39:19Z

0

for (int j=0; j<this.b; j++)
    {
        System.out.print("Matrice " + l + " ["+ i +"]["+ j +"]= ");
        this.mat[l][i][j]=citast.nextInt();
    }

If you leave

this.mat[l][i][j] = citast.nextInt();

out of it, then it's working.

Also you have to make Final() static and declare c and d in your class, because they are in the constructor, but there is no reference to them in the class.

edited Nov 24, 2013 at 15:39

answered Nov 24, 2013 at 15:30

WonderWorld

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