09. Combine Lists Of Letters

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


public class _09_CombineListsOfLetters {

    public static void main(String[] args) {
        try (Scanner scanner = new Scanner(System.in)) {
            ArrayList<Character> list1 = new ArrayList<>();
            ArrayList<Character> combinedList = new ArrayList<>();
            // read chars from first list;
            // with "replaceAll" method remove all whitespace
            for (char c : scanner.nextLine().replaceAll("\\s+", "").toCharArray()) {
                list1.add(c);
            }
            combinedList.addAll(list1);
            // add chars from second list to combined one,
            // but only those chars, which do not exist in first list
            for (char c : scanner.nextLine().replaceAll("\\s+", "").toCharArray()) {
                if (!list1.contains(c)) {
                    combinedList.add(c);
                }
                // there's no need to save these chars
            }
            // print combined list
            for (char c : combinedList) {
                System.out.print(c + " ");
            }
        } catch (Exception e) {
            e.printStackTrace();
        }

    }

}