05 - Control Flow Loops

Loops let you repeat code without writing it over and over. They're essential for processing collections, generating worlds, and updating game objects.

While Loop

Repeats code while a condition is true:


int countdown = 5;

while (countdown > 0) {
    System.out.println(countdown);
    countdown--;
}
System.out.println("Blast off!");

Structure

while (condition) {
    // code to repeat
}

Infinite Loops

Always make sure your loop condition will eventually become false, or your program will run forever!

int x = 0;
while (x < 10) {
    System.out.println("Stuck!");
    // Forgot to increase x!
}

Do-While Loop

Like a while loop, but always runs at least once:

int health = 0;

do {
    System.out.println("Attempting respawn...");
    health = 100;
} while (health <= 0);

For Loop

Best when you know how many times to repeat:

for (int i = 1; i <= 5; i++) {
    System.out.println("Level " + i);
}

Structure

for (initialization; condition; update) {
    // code to repeat
}

For Loop Parts

for (int i = 0; i < 10; i++) {
//   ^         ^        ^
//   Start     Stop     Step
}

Initialization: int i = 0 - Runs once at the start
Condition: i < 10 - Checked before each loop
Update: i++ - Runs after each loop

Break Statement

You can exit a loop early with break:


for (int i = 1; i <= 10; i++) {
    if (i == 6) {
        break; // Exit loop when i is 6
    }
    System.out.println(i);
}

Continue Statement

Skip to the next iteration with continue:

for (int i = 1; i <= 10; i++) {
    if (i % 2 == 0) {
        continue; // Skip even numbers
    }
    System.out.println(i); // Prints only odd numbers
}

Nested Loops

You can put loops inside other loops:

for (int i = 1; i <= 3; i++) {
    for (int j = 1; j <= 2; j++) {
        System.out.println("i: " + i + ", j: " + j);
    }
}

Nested Loop Performance

Be careful with nested loops! They can slow down your mod significantly.

// This runs 1,000,000 times!
for (int i = 0; i < 1000; i++) {
    for (int j = 0; j < 1000; j++) {
        // Code here
    }
}

Try to avoid deeply nested loops when processing large amounts of data.

05 - Control Flow Loops

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