[Java Basics][Collections-HW] 09. Combine Lists of Letters

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

public class CombineListsOfLetters {

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);

        String firstLine = sc.nextLine();
        String secondLine = sc.nextLine();

        String[] firstStrArr = firstLine.split(" ");
        String[] secondStrArr = secondLine.split(" ");

        ArrayList<Character> l1 = new ArrayList<>();
        ArrayList<Character> tempList = new ArrayList<>();
        ArrayList<Character> l2 = new ArrayList<>();

        for (int i = 0; i < firstStrArr.length; i++) {
            l1.add(i, firstStrArr[i].charAt(0));
        }
        tempList.addAll(l1);

        for (int i = 0; i < secondStrArr.length; i++) {
            l2.add(i, secondStrArr[i].charAt(0));
        }
        for (int i = 0; i < l2.size(); i++) {
            if(!(tempList.contains(l2.get(i)))) {
                l1.add(l2.get(i));
            }
        }
        for (Character character : l1) {
            System.out.print(character + " ");
        }
    }
}