We develop a static method, matrixSum(), that takes as parameters two matrices A and B of doubles, and returns a new matrix obtained by summing corresponding elements of A and B. We assume that A and B have the same dimensions (i.e., the same number of rows and the same number of columns).
public static double[][] matrixSum(double[][] A, double[][] B) { double[][] C = new double[A.length][A[0].length]; for (int i = 0; i < A.length; i++) for (int j = 0; j < A[0].length; j++) C[i][j] = A[i][j] + B[i][j]; return C; }
Note that, in order to access all elements of the matrices A and B, we use two nested for loops: the outermost one iterates over the rows (i), while the innermost one iterates over the elements of each row (j).
Example of usage:
public static void main(String[] args) { double[][] A = { // creates matrix A of dimension 2x3 { 1.2, 2.3, 2.3 }, // row 0 of A (array of 3 double) { 7.4, 5.1, 9.8 } // row 1 of A (array of 3 double) }; double[][] B = { // creates matrix B of dimension 2x3 { 5.0, 4.0, 1.3 }, // row 0 of B (array of 3 double) { 1.2, 0.3, 3.2 } // row 1 of B (array of 3 double) }; double[][] C = matrixSum(A,B); // calculates the sum of A and B System.out.println(C[1][0]); // prints out 8.6 }