While Loops

The Three Steps of a Loop

A while loop repeats its body as long as a condition holds, checked before every pass, including the first:

int attempts = 0;             // 1. initialize
while (attempts < 3 && !connected) { // 2. test
    connected = tryConnect();
    attempts++;                // 3. update
}

Every loop needs these same three steps — initialize the loop variable, test it, update it inside the loop. A for loop (Lesson 5.1-5.2) just packs all three into one header line; a while loop spreads them out, which is more natural when the "update" isn't a simple counter.

Infinite Loops

Forget step 3 and the condition never changes — the loop runs forever:

int i = 0;
while (i < 10)
{
    System.out.println(i); // i never changes — this never stops
}

An infinite loop on a robot doesn't just print forever — it can freeze the whole robot's control loop, since nothing after it ever gets a chance to run.

When to Reach for `while` Instead of `for`

for fits naturally when you already know the number of iterations. while fits better when you're waiting for a condition, not counting to a number — like waiting for a sensor to settle, or retrying a connection a limited number of times:

while (!gyro.isConnected() && attempts < 5)
{
    attempts++;
}

Common Pitfalls

Forgetting to update the loop variable. The single most common cause of an infinite loop — every while loop needs something inside it that eventually makes the condition false.
A condition that's false from the very first check. If the condition never holds, the loop body never runs at all — not even once. Double-check the loop variable's starting value against the condition.

Key Takeaways

Every loop needs three steps: initialize, test, update — while just doesn't bundle them into one line like for does.
A while loop's condition is checked before every pass, including the first — if it starts false, the body never runs.
Forgetting to update the loop variable is the classic cause of an infinite loop, which can freeze a robot's control code.
while fits naturally when you're waiting for a condition rather than counting a known number of iterations.

Derived from csawesome-2026: unit-2-selection-and-iteration/2.07-while-loops.md (CSA 2.7)