How to multiply a matrix already created with random numbers to itself ?

Question

Hello everyone. I created a matrix with random integers and I have to multiply this matrix to itself and print it. And I have to do the multiplication in an another method. Here is my code :
public class Deneme21 {

/**
* @param args the command line arguments
*/
public static void main(String[] args) {
// TODO code application logic here
int [][]a = new int [10][10];

gunesF(a);
}
/**
*
* @param sayi
* @return
*/
public static boolean isPrime(int sayi){
boolean sonuc = true;
for (int i = 2; i < sayi; i++){
if (sayi % i == 0){
sonuc = false;
break;
}
}
return sonuc;
}

public static void gunesF(int [][] a) {

Random randomNum = new Random();

for (int x = 0; x < 10; x++){
for (int y = 0; y < 10; y++){
int s;
s = randomNum.nextInt(100);
a[x][y] = s;
}
}
for (int x = 0; x < 10; x++){
for (int y = 0; y < 10; y++){
if (isPrime(a[x][y])){
System.out.print(a[x][y] + "* ");
} else {
System.out.print(a[x][y] + " ");
}
}
System.out.println(" ");
}
}
}

Answer 1

What is the isPrime() method for though? are you only multiplying when a certain element's value was a prime number?

Answer 2

Martin Taylor
Does a[x][y] = a[x][y] * a[x][y] ; works for matrix multiplication?
This will multiply the numbers with itself but I think Güneş Özkan want the matrix multiplication.

Answer 3

Ipang No man it is for checking the random integer if it is prime number or not, when it is prime, the number has got an asteriks over it.

Answer 4

Okay then, Martin's suggestion is good. I'd go his way for this case also 👌