Java判断质数、求所有约数【蓝桥杯常用方法】

public static boolean isPrime(int n){
            for (int i = 2; i <= Math.sqrt(n) ; i++) {
                if(n%i==0){
                    return false;
                }
            }
            return true;
}

public static HashSet<Long> getFac(long n){
HashSet<Long> set = new HashSet<>();
        for (long i = 1; i <= (long)Math.sqrt(n); i++) {
            if(n%i == 0){
                set.add(i);
                set.add(n/i);
            }
        }
}