public static boolean sameShape(int[][] matrixA, int[][] matrixB) {
      
    // check if # of rows is same 
    if (matrixA.length != matrixB.length) 
        return false; // error 
      	
    // for each row, check if # cols is same 
    for (int row = 0; row < matrixA.length; row++) 
        if (matrixA[row].length != matrixB[row]) 
            return false; // error 
      	
    return true;
}
    

int[][] sum;

// first check that A and B have the same shape
if (sameShape(A, B) { 
    // assume all rows have same number of columns 
    sum = new int[A.length, A[0].length]; 
    
    // compute A + B 
    for (int row = 0; row < A.length; row++) 
        for (int col = 0; col < A[row].length; col++) 
            sum[row][col] = A[row][col] + B[row][col];
}
else 
    System.out.println("Can't add matrices of different sizes");