AP04_HW/HW01/PrimeFactors_05.java

import java.util.Scanner;
import java.util.ArrayList;

public class PrimeFactors {
    public static ArrayList<Integer> Factors(int num){
        ArrayList<Integer>  factors = new ArrayList<>();

        if (num <= 1){
            System.out.println("no prime factor!.");
        }

        while (num%2 == 0){
            factors.add(2);
            num /= 2;
        }
        for(int i = 3; i*i <= num; i+=2){
            while (num%i == 0){
                factors.add(i);
                num /= i;
            }
        }
        if (num > 1 ){
            factors.add(num);
        }
        return factors;
    }
    public static void main(String[] args){
        Scanner sc = new Scanner(System.in);
        int number = sc.nextInt();
        ArrayList<Integer> factors = Factors(number);
         if (!factors.isEmpty()){
             System.out.println("factors =  "+ factors);
         }
    }
}