Loops

A loop lets a program repeat a block of code multiple times, without having to manually write that code over and over. Java provides a few different kinds of loops, each suited to slightly different situations.

The for Loop

A for loop is best used when you know exactly how many times you want to repeat a block of code, such as iterating a fixed number of times.

For Loop Formula

for ([initialization]; [condition]; [update]) {
    [code to run each iteration]
}

for (int i = 0; i < 5; i++) {
    System.out.println("Motor check " + i);
}

The three parts of a for loop run in a specific order:

1. Initialization: int i = 0; runs once, before the loop starts
2. Condition: i < 5; is checked before every iteration; the loop stops once it's false
3. Update: i++ runs after every iteration

The while Loop

A while loop is best used when you don't know exactly how many times you need to repeat, and instead want to keep looping as long as some condition remains true.

While Loop Formula

while ([condition]) {
    [code to run each iteration]
}

int velocity = 0;

while (velocity < 10) {
    velocity += 2;
    System.out.println("Velocity: " + velocity);
}

The condition is checked before every iteration, including the very first one. If the condition is false from the start, the loop body never runs at all.

The do-while Loop

A do-while loop is similar to a while loop, except the condition is checked after the loop body runs, guaranteeing that the code inside runs at least once.

Do-While Loop Formula

do {
    [code to run each iteration]
} while ([condition]);

int attempts = 0;

do {
    System.out.println("Attempt " + attempts);
    attempts++;
} while (attempts < 3);

Choosing the Right Loop

Loop	Best used when...
for	You know the exact number of iterations ahead of time
while	You want to loop based on a condition, and might not loop at all
do-while	You want to loop based on a condition, but need it to run at least once

A Preview: The Enhanced for Loop

Java also provides a special version of the for loop, called the enhanced for loop (or "for-each" loop), which is used to iterate over every element in a collection, such as an array or ArrayList, without needing to manually track an index.

for (int motorId : motorIds) {
    System.out.println("Motor ID: " + motorId);
}

This loop is covered in much more detail in the Data Structures section, once collections like arrays and ArrayList have been introduced.