Program is to calculate the prime factorization, the prime factorization theorem

Question

Program is to calculate the prime factorization, the prime factorization theorem states that every positive integer is uniquely factorable into a product of prime numbers. The below code is set to calculate only for the number 40. Please alter code to ask the user to enter a number, then take that number and calculate the prime factorization.

import java.util.*;

public class PrimeFactorization {

public static void main(String[] args) {

ArrayList<Integer> factors = new ArrayList<>();

// adding 1 in list
factors.add(1);

int s = 2;

int num = 40;

int n = num;

// loop till divisors is less than dividend
while (s <= n) {

// divide n by s till it is divisible
while (n != 1 && n % s == 0) {

factors.add(s);

n = n / s;

}

s = s + 1;

}

factors.add(num); // adding number itself in list

System.out.println(factors);

// finding factors
for (int i = 1; i <= num; i++) {

if (num % i == 0) {
System.out.print(i + " ");
}

}

System.out.println();

}

}

Explanation / Answer

import java.util.*;
public class PrimeFactorization {
public static void main(String[] args) {
ArrayList<Integer> factors = new ArrayList<>();
// adding 1 in list
factors.add(1);
int s = 2;
System.out.print("Enter a positive interger:");
Scanner scan = new Scanner(System.in);
int num = scan.nextInt();
int n = num;
// loop till divisors is less than dividend
while (s <= n) {
// divide n by s till it is divisible
while (n != 1 && n % s == 0) {
factors.add(s);
n = n / s;
}
s = s + 1;
}
factors.add(num); // adding number itself in list
//System.out.println(factors);
// finding factors
for (int i = 1; i <= num; i++) {
if (num % i == 0) {
System.out.print(i + " ");
}
}
System.out.println();
}
}

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