### Program for Matrix multiplication in Java.

Note:  Step 1: Make sure that the the number of columns in the 1st one equals the number of rows in the 2nd one. (The pre-requisite to be able to multiply)

Step 2: Multiply the elements of each row of the first matrix by the elements of each column in the second matrix.

public class MatrixMultiplication {

public static void main(String args[]) {
int a[][] = new int[3][3];
int b[][] = new int[3][3];
int mul[][] = new int[3][3];
int sum = 0;
Scanner sc = new Scanner(System.in);

System.out.println("Enter element of First Matrix ");
for (int i = 0; i <= 2; i++) {

for (int j = 0; j <= 2; j++) {
a[i][j] = sc.nextInt();

}
}
System.out.println("Value of  Matrix is ");
for (int i = 0; i <= 2; i++) {

for (int j = 0; j <= 2; j++) {
System.out.print(a[i][j] + " ");

}
System.out.println();
}

System.out.println("Enter element of Second Matrix ");
for (int i = 0; i <= 2; i++) {

for (int j = 0; j <= 2; j++) {
b[i][j] = sc.nextInt();

}
}
System.out.println("Value of Second Matrix is ");
for (int i = 0; i <= 2; i++) {

for (int j = 0; j <= 2; j++) {
System.out.print(b[i][j] + " ");

}
System.out.println();
}

//Logic for matrix multiplication

for (int k = 0; k < 3; k++)
{
for (int i = 0; i < 3; i++)
{
for (int j = 0; j < 3; j++)
{
sum=sum+(a[k][j]*b[j][i]);
}
mul[k][i]=sum;
sum=0;
}
}

System.out.println("Multiplication of both Matrix is ");
for (int i = 0; i <= 2; i++) {

for (int j = 0; j <= 2; j++) {
System.out.print(mul[i][j] + " ");

}
System.out.println();
}

}

}

Output:

Enter element of First Matrix
1
2
3
4
5
6
7
8
9

Value of  Matrix is
1 2 3
4 5 6
7 8 9

Enter element of Second Matrix
1
2
3
4
5
6
7
8
9

Value of Second Matrix is
1 2 3
4 5 6
7 8 9

Multiplication of both Matrix is
30 36 42
66 81 96
102 126 150