Prime visits problem doubt

what are the mistakes in my code:
import java.util.*;
public class Main {
public static void main(String args[]) {
Scanner cin = new Scanner(System.in);
int t = cin.nextInt();
while(t>0){
int count = 0;
ArrayList alist = new ArrayList();
long a = cin.nextLong(),b = cin.nextLong();
for(long i = a;i<=b;i++){
for(long j =a;j<=i;j++){
if(i%j == 0){
count ++;
}
}
if(count == 2){
alist.add(i);
}
}
System.out.println(alist.size());
t–;
}
}
}

  1. You don’t need to take ‘long’, just take ‘int’

here ‘j’ should be initialized with 1, not a.
3)

This should be initialized as 'ArrayList<Integer> alist = new ArrayList<>();
4) You will have to make your algorithm more efficient otherwise all test cases will not pass. For example, you could run the second loop till sqrt(i) or use Sieve of Eratosthenes

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