Для -1,0,1,150 все работает корректно.
package com.javarush.task.task15.task1531;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.math.BigInteger;
/*
Факториал
*/
public class Solution {
public static void main(String[] args) throws IOException {
BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));
int input = Integer.parseInt(reader.readLine());
reader.close();
System.out.println(factorial(input));
}
public static int k = 0;
public static String factorial(int n) {
if (k == 0) k = n;
BigInteger bn = BigInteger.valueOf(n);
BigInteger answ = BigInteger.ZERO;
if (n == 0) {
System.out.print(k + "! = ");
return "1";
}
if (n > 0) {
answ = bn.multiply(new BigInteger(factorial(n - 1)));
} else {
System.out.print("0! = ");
return "1";
}
return answ.toString();
}
}