object that contains 2dimensional double array-user input

Question

I am fairly new to java and I have a problem with following program:

 import java.util.Scanner;

public class Matrix2D { 

private double[][] matrix; 
private int dimX; 
private int dimY;   



public Matrix2D(int row , int col ){  
    Scanner scanner=new Scanner(System.in);
    dimX=col; 
    dimY=row;
    matrix=new double[row][col]; 
    int i ,j;
    for( i=0;i<matrix[row].length;i++) 
    { 
        for( j=0;j<matrix[col].length;j++) 
        {   
            System.out.println("Please enter double at position"+" "+ row +" "+ col);  
            double input=scanner.nextDouble();
            matrix[row][col]=input;  }
    }


}


public static void main(String[] args) {
    Matrix2D test=new Matrix2D(3 ,3 );

}

}

Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: 3
    at Matrix2D.<init>(Matrix2D.java:17)
    at Matrix2D.main(Matrix2D.java:31)

The program lets me give the first user input , but immediately after it throws the exception above. Any help would be much appreciated.

Eran · Accepted Answer · 2016-05-24 18:48:17Z

1

You got the indices of your loops mixed up. martix has row rows, with indices 0 to row-1, so matrix[row] is out of bounds.

It should be :

matrix=new double[row][col]; 
for(int i=0;i<row;i++) { 
    for(int j=0;j<col;j++) {   
        System.out.println("Please enter double at position"+" "+ i +" "+ j);  
        double input=scanner.nextDouble();
        matrix[i][j]=input;  
    }
}

or

matrix=new double[row][col]; 
for(int i=0;i<matrix.length;i++) { 
    for(int j=0;j<matrix[i].length;j++) {   
        System.out.println("Please enter double at position"+" "+ i +" "+ j);  
        double input=scanner.nextDouble();
        matrix[i][j]=input;  
    }
}

answered May 24, 2016 at 18:48

Eran

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1 Comment

williamsidis Over a year ago

thanks for the quick response.You were right , now the program works just fine. Thx

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