Daniel Finley - The AP Computer Science Tutor

Daniel Finley - The AP Computer Science Tutor I help students boost their confidence and score 5's on the AP Computer Science Exam

09/15/2026

The most dangerous method you'll write in this class isn't broken. It's just really convincing when it's wrong.

Binary search assumes the array is already sorted. It never checks. It just trusts you.

Hand it unsorted data and it still runs. Still finishes. Still hands you an answer with total confidence. That answer just happens to be wrong.

No exception. No red flag. Just a wrong number that looks completely fine.

Comment below if you've ever gotten burned by something that looked totally fine and wasn't 💻⚡️

09/14/2026

Her first practice tests were landing in the 3 to 4 range. She finished AP Computer Science A with a 5.

In her words, she kind of sucked at the beginning. She didn't fail. She just wasn't close to a 5 yet.

That's the honest starting point for most students who end up scoring one.

She was self studying before we met. Her online class covered the material but never taught to the exam, which is a distinction most families don't find out until the first practice test comes back.

Here's what actually moved her. Practice tests, then reviewing the questions she got wrong with someone who could explain why the wrong answer looked right.

A 3 in the fall says nothing about May. It only means the gap hasn't been worked yet, and there's a whole year to work it.

Comment APCOMPSCI below if your student is sitting in the 3 to 4 range right now 💻⚡️

09/12/2026

We just opened something new: 30 days free on the ACE AP CS Portal.

Full lesson library for AP CS A (Java) and AP CS Principles, built in practice sets, and progress tracking so you can see exactly where your teen stands before the exam.

We’re only opening this beta to the first 30 families and want your feedback. Once they’re in, the form closes.

Comment BETA and we’ll DM you the link.

—
Daniel · enginearu.com

AP® and Advanced Placement® are trademarks registered by the College Board, which is not affiliated with, and does not endorse, this content.

09/09/2026

Quick test. Pull out your planner right now. If the only things in there are due dates, you've already got a problem, and it's only a few weeks in.

Not because you're behind. Because you don't have a system yet.

It's never about willpower. The students who fall behind in October are the ones who never decided three things in September: where they work, when they review instead of just turning things in, and how they track what's still fuzzy.

Decide those now, while it's still easy. Not in six weeks when it isn't.

Comment below which one of those three you don't actually have yet 💻⚡️

09/07/2026

This nested loop looks like it runs 9 times. It actually runs 6.

The inner loop doesn't restart from zero every pass. It starts wherever the outer loop left off, and that one detail changes the whole count.

Most students guess 9 and move on. Tracing it, not reading it, is the only way to catch this before the exam does.

Comment below if you would've guessed 9 too 💻⚡️

09/03/2026

This program never stops running. Okay, not forever, but close enough that it might as well.

Recursion only stops when you give it an exit. Forget the base case and it spirals until Java crashes it for you.

Here's the actual test for which one you need: does the problem break into a smaller version of itself? That's recursion. Just repeating something a known number of times? That's iteration.

One of these can genuinely crash your program. The other can't.

Comment below if you've ever actually crashed something doing this 💻⚡️

09/01/2026

This loop never stops. And it's not a typo.

It's because whoever wrote it picked the wrong loop type before they even got to the logic.

Here's the rule that never changes: if you know the exact number of repeats before you start, that's a for-loop. If the loop itself decides when it's done, that's a while-loop.

Pick wrong and you won't get an error. It'll just run forever or stop too early, and you won't know why.

Comment below if you've ever picked the wrong one and had no idea what broke 💻⚡️

08/28/2026

"I ended up getting a five on the AP exam." 🎉

That's the highest score possible on AP Computer Science A — and Aarav earned it. This is the moment, in his own words.

Thinking about AP CSA for your teen this year? Comment "APCOMPSCI" and I'll send you the exact study plan behind results like this. 👇

08/19/2026

If the public key is public, how is your message secure?

This is the most misunderstood idea in the AP Computer Science Principles security unit, and it comes down to one thing.

Symmetric encryption uses one key for both jobs. It locks and it unlocks. Which means you have to somehow deliver that key to the other person first, and anyone who intercepts it can read everything.

Public key encryption uses a pair. The public key only locks. It can't open anything, not even what it just closed. The private key is the only thing that opens it, and it never gets sent anywhere.

That's why publishing your public key is safe. Anyone can lock a message to you. Nobody can open one.

Also worth knowing: College Board says the math behind encryption is out of scope. You won't encrypt anything by hand. You just need to know which key does which job.

Comment below with the CSP topic you want broken down next, security or networking 💻⚡️

08/17/2026

Make sure you go into AP Computer Science prepared.

Know which track you're in, CSA is Java and daily coding, CSP is broader concepts with less syntax. Don't coast through unit one just because it's easy, that's where you build the study habit you'll rely on all year. Practice reading code and predicting output, not just writing it. And build a weekly rhythm early, because this class stacks and you can't cram a subject that stacks.

The one that matters most: get help before you start struggling, not after. Every family that calls me in October is patching three units of gaps. The September families never build them.

You don't need any coding experience to start. You do need a plan.

Comment below if you're starting AP CSA or AP CSP this year, I want to know which one 💻⚡️

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