Get stair paths

I/P: 3

O/P: [111, 12, 21, 3]

import java.util.ArrayList;

public class GetStairPath {
    public static void main(String[] args) {
        int n = 3;
        ArrayList<String> ans = getStairPath(n);
        System.out.println(ans);
    }

    private static ArrayList<String> getStairPath(int n) {
        // base case
        if (n == 0) {
            ArrayList<String> bres = new ArrayList<>();
            bres.add("");
            return bres;   // iska size 1 hoga toh step append ho jaega isme
        } else if (n < 0) {
            ArrayList<String> bres = new ArrayList<>();
            return bres;    // iska size empty hoga toh kuch bhi add ni hoga ans me
        }

        // faith
        ArrayList<String> n1 = getStairPath(n - 1);
        ArrayList<String> n2 = getStairPath(n - 2);
        ArrayList<String> n3 = getStairPath(n - 3);

        // expectation meet faith
        ArrayList<String> ans = new ArrayList<>();

        for (String step : n1) {
            ans.add(step + "1");
        }
        for (String step : n2) {
            ans.add(step + "2");
        }
        for (String step : n3) {
            ans.add(step + "3");
        }
        return ans;
    }
}