A mind teaser: fill the digits once

[FredWe]

make it equal by filling each digit [1 ... 9] once in the block:
      a b
*       c
----------
      d e
+     f g
----------
=     h i

import java.io.*;
import java.util.*;

public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int[] nums = {1, 2, 3, 4, 5, 6, 7, 8, 9};
		helper(nums, new ArrayList());
        return;
    }
    public static void helper(int[] nums, List<Integer> tempPerm) {
    	if (nums.length == tempPerm.size()) {
    		int ab = tempPerm.get(0) * 10 + tempPerm.get(1);
    		int c = tempPerm.get(2);
    		int de = tempPerm.get(3) * 10 + tempPerm.get(4);
    		int fg = tempPerm.get(5) * 10 + tempPerm.get(6);
    		int hi = tempPerm.get(7) * 10 + tempPerm.get(8);
    		if (ab * c == de && de + fg == hi) System.out.println(tempPerm);
    	}
        for (int n: nums) {
        	if (tempPerm.contains(n)) continue;
        	tempPerm.add(n);
        	helper(nums, tempPerm);
        	tempPerm.remove(tempPerm.size() - 1);
        }
    }
}

>>  [1, 7, 4, 6, 8, 2, 5, 9, 3]