import java.util.*;

class AlphabetIterator implements Iterator<Character> {
    // keeps track of which one we're on and whether we are uppercase or not
    private char current;
    private boolean upper;
    
    // starts out on a or A
    public AlphabetIterator(boolean uppercase) {
        if (uppercase) {
            current = 'A';
        } else {
            current = 'a';
        }
        upper = uppercase;
    }

    // returns whether we have a next value in the sequence
    @Override
    public boolean hasNext() {
        if (upper) {
            return current <= 'Z';
        } else {
            return current <= 'z';
        }
    }

    // returns the next one in the sequence
    @Override
    public Character next() {
        Character val = Character.valueOf(current);
        current++;
        return val;
    }
}

class Alphabet implements Iterable<Character> {
    private boolean uppercase;

    public Alphabet(boolean uppercase) {
        this.uppercase = uppercase;
    }

    public Iterator<Character> iterator() {
        return new AlphabetIterator(uppercase);
    }
}

public class Letters {
    public static <T> int count(Iterable<T> stuff) {
        int num = 0;
        Iterator<T> it = stuff.iterator();

        while (it.hasNext()) {
            num++;
            it.next();
        }

        return num;
    }

    public static <T> ArrayList<T> reverse(Iterable<T> stuff) {
        ArrayList<T> reversed = new ArrayList<>();

        Iterator<T> it = stuff.iterator();
        while (it.hasNext()) {
            reversed.add(0, it.next());
        }

        return reversed;
    }

    public static void main(String args[]) {
        Alphabet letters = new Alphabet(true);
        for (Character c : letters) {
            System.out.println(c);
        }

        System.out.println(reverse(letters));

    }
}