Generate permutation of 2 string in ordered form

GeneratePermutation2Strings.java

public class GeneratePermutation2Strings {

    public static void main(String... arg) {
        Scanner scanner = new Scanner(System.in);
        String s1 = scanner.nextLine();
        String s2 = scanner.nextLine();

        generateSequence("", s1, s2);
    }

    private static void generateSequence(String prefix, String s1, String s2) {
        if(s1.length() + s2.length() == 0) {
            System.out.println(prefix);
        }

        if(s1.length() > 0) {
            String temp1 = s1.length() <= 1 ? "" : s1.substring(1, s1.length());
            generateSequence(prefix + (s1.length() > 0 ? s1.charAt(0) : ""),temp1 , s2);
        }

        if(s2.length() > 0) {
            String temp2 = s2.length() <= 1 ? "" : s2.substring(1, s2.length());
            generateSequence(prefix + (s2.length() > 0 ? s2.charAt(0) : ""), s1, temp2);
        }
    }
}