Help me in solving FCTRL2 problem

My issue

explain this code

My code

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import java.util.*;
import java.lang.*;
import java.math.*;

/* Name of the class has to be "Main" only if the class is public. */
class Codechef
	public static void main (String[] args) throws java.lang.Exception
             Scanner sc = new Scanner(;
             int t = sc.nextInt();
            while(t --> 0)
                int n = sc.nextInt();
                BigInteger fact = new BigInteger("1");
                for(int i = 2; i <= n; i++)
                fact = fact.multiply(BigInteger.valueOf(i));

Problem Link: FCTRL2 Problem - CodeChef

its a simple way for finding factorial by looping through the array.
We are type casting it as BigInteger because the answer can very large and can’t be fit inside int data type.