9. Combine Lists of Letters

/* Write a program that reads two lists of letters l1 and l2 and combines them:
 * appends all letters c from l2 to the end of l1, but only when c does not appear in l1.
 * Print the obtained combined list. All lists are given as sequence
 * of letters separated by a single space, each at a separate line.
 * Use ArrayList<Character> of chars to keep the input and output lists. */

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

public class _09_CombineListsOfLetters {

    public static void main(String[] args) {
        // TODO Auto-generated method stub
        Scanner scan = new Scanner(System.in);
        System.out.println("Enter sequence of letters to the First list on single line, separated by a space:");
        String firstLine = scan.nextLine();
        System.out.println("Enter sequence of letters to the Second list on single line, separated by a space:");
        String secondLine = scan.nextLine();

        String[] firstArr = firstLine.split("[^a-zA-Z]");
        String[] secondArr = secondLine.split("[^a-zA-Z]");

        ArrayList<Character> combinedList = new ArrayList<>();
        ArrayList<Character> secondList = new ArrayList<>();
        for (int i = 0; i < firstArr.length; i++) {
            char letter = firstArr[i].charAt(0);
            combinedList.add(letter);
        }

        for (int i = 0; i < secondArr.length; i++) {
            char letter = secondArr[i].charAt(0);
            if (!combinedList.contains(letter)) {
                secondList.add(letter);
            }
        }

        combinedList.addAll(secondList);
        System.out.println("The obtained combined list is:\n" + combinedList);
    }

}