Tokens and boxing

String tokens inside Q3 — the exam loves lists of words:

"Count words that start and end with the same letter"

public int sameEnds(ArrayList<String> words) {
    int count = 0;
    for (String w : words) {
        if (w.length() > 0 && w.charAt(0) == w.charAt(w.length() - 1)) {
            count++;
        }
    }
    return count;
}

Two obligations hide in one line: the guard w.length() > 0 (empty strings are legal elements!) and the first/last comparison. Swap charAt order and nothing changes; forget the guard and a single empty-string element throws — the test that separates 8 from 9.

Autoboxing in Q3 answers: ArrayList<Integer> totals need no special handling (int sum += list.get(i) unboxes), but equals still beats == when the spec says "the Integer equal to" — for small values they agree; for exam values, write .equals or unbox explicitly.

Mutating Q3 — when the question says "remove", the answer is the backward loop (Module 7) wearing a Q3 wrapper class. The provided class never changes the rules of mutation.