2614. Prime In Diagonal

```java
class Solution {
    public boolean[] getPrimes(int n) {
        boolean[] primes = new boolean[n];
        Arrays.fill(primes, true);
        primes[0] = false;
        primes[1] = false;
        for (int i = 2; i*i < n; i++) {
            if (primes[i]) {
                for (int j = i*i; j < n; j+=i) {
                    primes[j] = false;
                }
            }
        }
        return primes;
    }
    public int diagonalPrime(int[][] nums) {
        boolean[] isPrime = getPrimes(4000001);
        int ans = 0;
        for (int i = 0; i < nums.length; i++) {
            int a = nums[i][i];
            int b = nums[i][nums.length - i - 1];
            if (isPrime[a]) {
                ans = Math.max(ans, a);
            }
            if (isPrime[b]) {
                ans = Math.max(ans, b);
            }
        }
        return ans;
    }

}
```