Combine Lists of Letters

import java.util.Scanner;

public class Problem_09_CombineListsOfLetters {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        String firstText = scanner.nextLine();
        String secondText = scanner.nextLine();
        StringBuilder sb = new StringBuilder();
        sb.append(firstText+ " ");
        for (int i = 0; i < secondText.length(); i++) {
            for (int j = 0; j < firstText.length(); j++) {
                if (secondText.charAt(i) == firstText.charAt(j)) {
                    break;
                }
                if (j == firstText.length()-1) {
                sb.append(secondText.charAt(i)+" ");
                }
            }
        }
        System.out.println(sb);
    }
}