AP Computer Science A 3-Day Cram Plan

You have three days until the AP Computer Science A exam. This is not the time to learn recursion from scratch — it's time to drill the highest-frequency Java patterns and lock in the FRQ templates the College Board reuses every year.

This plan assumes ~4 focused hours per day. Skip nothing on the checklist; if you're short on time, shorten the practice sets, not the topic coverage.

Day 1: Primitives, Objects, and Classes (4 hrs)

The first ~20 multiple-choice questions lean on understanding variables, objects, and how to write methods.

What to review (90 min)

• Primitive types: int, double, boolean — declaration, initialization, assignment.
• Integer division and modulo: 7 / 2 = 3, 7 % 2 = 1. This trap appears on almost every exam.
• String methods: .length(), .substring(), .indexOf(), .compareTo(), .equals() vs ==.
• Math class: Math.abs(), Math.max(), Math.min(), Math.pow(), Math.random().
• Writing a class: constructor, instance variables, this keyword, instance methods, static variables.
• Scope and visibility: public, private, local variables inside methods.

What to practice (2.5 hrs)

• Write 3 simple methods: one that uses integer division, one that manipulates a String, one that uses Math.random().
• Write 1 complete class with a constructor and 2 instance methods.
• 15 multiple-choice on primitives and object instantiation.

💡 Highest leverage: Integer division mistakes appear on every exam. Drill 5 problems where you compute a / b and a % b together.

Day 2: Arrays, ArrayLists, and Traversal (4 hrs)

These two structures account for nearly half of all AP CS A points. You must know both forwards and backwards.

What to review (90 min)

• 1D Arrays: declaration (int[] arr = new int[10]), access, traversal with for-loops.
• Common array algorithms: find max/min, sum all elements, count matches, swap, reverse.
• ArrayList basics: add, remove, get, set, size — and that ArrayList uses generics (ArrayList<Integer> not ArrayList).
• Traversal patterns: enhanced for-loop vs index-based for-loop vs while-loop.
• The remove trap: removing during iteration can skip elements; use remove(index) carefully.
• 2D arrays: row-major order, nested for-loops, accessing arr[row][col].

What to practice (2.5 hrs)

• 1 FRQ-style problem: write a method that takes an array and returns the index of the max element.
• 1 FRQ-style problem: write a method that takes an ArrayList, removes all even numbers, and returns the size.
• 1 2D array problem: write a method that sums all elements in a 2D array.
• 20 multiple-choice on arrays and ArrayLists.

⚠️ FRQ trap: When removing from an ArrayList during iteration, your index will skip elements. Either iterate backwards, use an iterator, or build a new ArrayList instead.

Day 3: Inheritance, Recursion, and Full FRQ Timed Practice (4 hrs)

What to review (90 min)

• Inheritance: extends keyword, super() call in constructor, method overriding.
• Polymorphism: a subclass object in a superclass variable, calling overridden methods.
• The Object class: .equals(), .toString(), .hashCode() — know what you're overriding.
• Recursion basics: base case, recursive case, the call stack, tracing a recursive method by hand.
• Common recursive patterns: factorial, sum of array, binary search.

What to practice (2.5 hrs — full timed set)

• Trace 2 recursive methods by hand (write out 5-7 steps of the call stack).
• Write 1 recursive method (e.g., sum of an array, or count a character in a string).
• 1 full FRQ timed (methods and control structures, 10 min).
• 1 full FRQ timed (class design with inheritance, 10 min).
• 25 mixed multiple-choice (high-frequency topics), strictly timed.

💡 Recursion on Day 3: If you're weak on recursion, spend 30 min here and accept you may lose 2-3 points. Don't sacrifice array mastery to learn recursion from scratch.

The night before

Skim our last-minute review checklist. Get 8 hours of sleep — tomorrow your brain must parse Java syntax cleanly, and fatigue turns == into .equals() blindness.

Common point-leaks (prevent these)

• Using == to compare Strings instead of .equals().
• Integer division instead of casting to double before division.
• Forgetting to return from a method.
• ArrayList remove during a forward iteration (skip next element).
• Off-by-one errors in array loops and substring calls.
• Null pointer exceptions from accessing uninitialized objects.

What this 3-day plan deliberately skips

You will not fully master advanced recursion patterns or deep inheritance hierarchies in 3 days. If you're shaky there: do 2 worked examples, trace 1 complex recursive call, and accept you may lose a few points. Spend the saved time mastering array traversal and basic class design instead.

Ready to start?

Open the AP Computer Science A topic library → and start with Day 1 if you're weak on classes, or Day 2 if you're weak on arrays. Mix in 2-3 FRQ practice problems. You've got this.

Related guides:

• 7-day study plan
• FRQ practice guide
• Last-minute review