Question

I wrote this matrix addition program and I dont know why but I keep getting this two errors on lines 61 and 63 and i dont want to handle the exceptions but just throwing would do

error: unreported exception IOException; must be caught or declared

The code of the program is as follows:

import java.io.*;
class Arr
{
    int r,c;
    int arr[][];

    Arr(int r,int c)
    {
        this.r=r;
        this.c=c;
        arr=new int[r][c];
    }

    int[][] getMatrix()throws IOException
    {
        BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
        for(int i=0;i<r;i++)
        {
            for(int j=0;j<c;j++)
            {
                System.out.println("enter element");
                arr[i][j]=Integer.parseInt(br.readLine());
            }
        }
        return arr;
    }

    int[][] findsum(int a[][],int b[][])
    {
        int temp[][]=new int[r][c];
        for(int i=0;i<r;i++)
            for(int j=0;j<c;j++)
                temp[i][j]=a[i][j]+b[i][j];
        return temp;
    }

    void putmatrix(int res[][])
    {
        for(int i=0;i<r;i++)
        {
            for(int j=0;j<c;j++)
            {
                System.out.println(res[i][j]+"\t");
            }
        }
        System.out.println();
    }

}


class Matrixsum
{
    public static void main(String args[])
    {
        Arr obj1=new Arr(3,3);
        Arr obj2=new Arr(3,3);

        int x[][],y[][],z[][];
        System.out.println("\nEnter matrix 1");
        x=obj1.getMatrix();
        System.out.println("Enter matrix 2");
        y=obj2.getMatrix();
        z=obj1.findsum(x,y);
        System.out.println("the sum matrix is");
        obj2.putmatrix(z);
    }
}

Answer 1

1. getMatrix() is declared to throw IOException. Calls to getMatrix() in main() can generate IOExceptions, which are required to be caught by the function or rethrown. To solve the problem, you could declare main() to throw IOException.

2. The design of class Arr is a bit strange. Instead of using two redundant objects obj1 and obj2, you should condense it to one object, say one called arrProcessor. So the calls would look like:

   x=arrProcessor.getMatrix();
   y=arrProcessor.getMatrix();
   z=arrProcessor.findSum(x,y);
   arrProcessor.putMatrix(z);
   

Even better, instead of using arrays, you should wrap the arrays in objects, say in a class called Matrix:

public class Matrix{
    int[][] values;
    int numRows, numCols;

    protected Matrix(){/*...*/}

    public static Matrix getMatrix(int nRows, int nCols){/*...*/}
    public static Matrix addMatrices(Matrix a, Matrix b) throws Exception {/*...*/}

    public void print(){/*...*/}
    public void plus(Matrix another) throws Exception {/*...*/}
}

So now the code would look like:

Matrix x,y,z;
x=Matrix.getMatrix(3,3);
y=Matrix.getMatrix(3,3);
z=x.plus(y);
z.print();