Integers in lists

ArrayLists hold objects, so ArrayList<Integer> stores Integer boxes — and arithmetic quietly unboxes them:

ArrayList<Integer> nums = new ArrayList<Integer>();
nums.add(7);
int x = nums.get(0) + 1;          // unboxes to int, x = 8
Integer boxed = nums.get(0);
if (boxed == 7) { ... }           // true: unboxing comparison
if (nums.get(0) == new Integer(7)) { ... }  // int comparison, true

But between two Integers, == compares references:

Integer a = 200, b = 200;
if (a == b) { }          // false outside the small-value cache!
if (a.equals(b)) { }     // true — always compare objects with equals

(The small-value cache makes -128..127 sometimes compare equal with == — a trap that only looks reliable in tests.)

The exam's ArrayList FRQ always wraps a real class:

ArrayList<Member> roster = new ArrayList<Member>();
for (Member m : roster) {
    if (m.getPoints() >= threshold) { count++; }
}

For-each is perfect for reading; the moment you must remove, switch to an indexed loop. And the length-vs-size discipline: arrays use .length (no parens), Strings use .length(), ArrayLists use .size().