Stage 0: Loops

examples/stage0/snippets/src/Loops.java

@@ -0,0 +1,70 @@
+/*
+ * Copyright 2026 FRCSoftware
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ */
+
+class Drivetrain {
+    public void setThrottle(double speed) {}
+}
+
+boolean condition = false;
+Drivetrain drivetrain = new Drivetrain();
+
+void main() {
+    // [whileSyntax]
+    while (condition) {
+        // code to run when condition is true
+    }
+    // [/whileSyntax]
+
+    {
+        // [whileExample]
+        int i = 0;
+        while (i < 6) {
+            System.out.println(i); // prints 0, 1, 2, 3, 4, 5
+            i++;
+        }
+        // [/whileExample]
+    }
+
+    // [whileExample2]
+    int timer = 0;
+
+    while (timer <= 5) {
+      if (timer < 5) {
+        System.out.println("Drive Forward");
+      } else {
+        System.out.println("Stop Driving");
+      }
+      timer++;
+    }
+    // [/whileExample2]
+
+
+    {
+        // [ForExample1]
+        int i = 0;
+        while (i < 6) {
+            System.out.println("Hi!");
+            i++;
+        }
+        // [/ForExample1]
+    }
+
+    // [ForExample2]
+    for (int i = 0; i < 6; i++) {
+    System.out.println("Hi!");
+    }
+    //[/ForExample2]
+
+    // [forExample]
+    for (int i = 0; i < 5; i++){
+        System.out.println(i); // prints 0, 1, 2, 3, 4
+    }
+    // [/forExample]
+
+
+
+
+}

src/config/sidebarConfig.ts

@@ -69,10 +69,10 @@ export const sidebarSections: Record<string, SidebarSection[]> = {
                             label: 'Conditionals',
                             slug: 'learning-course/stage0/conditionals',
                         },
-                        // {
-                        //     label: 'Loops',
-                        //     slug: 'learning-course/stage0/loops',
-                        // },
+                        {
+                            label: 'Loops',
+                            slug: 'learning-course/stage0/loops',
+                        },
                         {
                             label: 'Classes, Fields, and Methods',
                             slug: 'learning-course/stage0/classes-methods',

src/content/docs/learning-course/stage0/loops.mdx

@@ -0,0 +1,205 @@
+---
+title: Loops
+description: An Intro loops in Java
+prev: learning-course/stage0/conditionals
+next: learning-course/stage0/classes-methods
+codeRegionSources:
+    default: stage0/snippets/src/Loops.java
+---
+
+Oftentimes in code, there is a need to repeat the same action multiple times in a row.
+For instance, if you know your grades are about to be released, you might repeatedly check them until they come out.
+In Java we can use loops to do this.
+
+In this lesson, we're going to cover two main types of loops: **while** loops and **for** loops.
+
+<Aside type="note">
+    There is another type of loop, the do-while loop. We will not be covering it
+    because it isn't commonly used in FRC. However, if you want to learn more
+    about do while loops, you can learn more on w3school's page on [do while
+    loops](https://www.w3schools.com/java/java_while_loop_do.asp)
+</Aside>
+
+Conditionals and loops may seem similar but they have different purposes.
+Conditionals and loops both control the flow of programs.
+Conditionals are used to run a block of code once, whereas a loop can run a block of multiple times
+
+## while
+
+`while` loops are the most simple type of loops.
+
+The syntax of a `while` loops is as shown:
+
+```java #whileSyntax
+
+```
+
+You might notice that a `while` loop looks very similar to the `if` conditional, which was discussed in the previous lesson.
+A `while` loop includes:
+
+- the `while` keyword to declare that we're making a `while` loop
+- `( )` to hold the condition that is either true or false.
+  Example: (5 > 1) is a condition and it is true because 5 is greater than 1
+- `{` to denote the opening of the loop's code block
+- `}` to denote the end of the loop's code block
+
+The following flowchart demonstrates how a while loop works:
+
+<ContentFigure
+    src="/learning-course/stage0/loops/WhileLoop.webp"
+    width="300px"
+    height="300px"
+/>
+
+Like the `if` conditional, the `while` loop will run its code block if the condition is true.
+Unlike the `if` conditional, however, when the code block is done, the `while` loop will evaluate its condition again.
+If the condition is still true, the code block will run again.
+This will repeat until the condition is false.
+Also unlike the `if` conditional, a `while` loop (or any other type of loop) can't have any `else` statements attached.
+This means that if the condition is false when the loop is first encountered, the entire thing is skipped.
+
+Let's look at an example:
+
+```java #whileExample
+
+```
+
+In the example, there is an `int` called `i` which holds the value 0. The `while` loop has the condition `i < 6`.
+First, the compiler checks if the condition is true.
+We know that 0 is less than 6 so the `while` code block runs and the value of `i`, which is currently 0, is printed to the terminal.
+The value of `i` is also updated because of `i++` and it changes to 1.
+Now the condition checks if 1 is less than 6. We know that it is true, so the value of `i` gets printed and the value of `i` is increased by 1.
+This repeats and eventually `i`'s value becomes 6.
+Now, when the condition is evaluated, it's `false`, as 6 is not less than 6, so the loop is complete.
+
+<Aside type="tip">
+    Does the ``i++`` look familiar? This was covered in the operator section. If
+    you need a refresher on what an operator is and how it works, check out the
+    operator page.
+</Aside>
+
+Lets look at an another example!
+In the example below we have:
+
+```java #whileExample2
+
+```
+
+Without running the code, what do you think happens?
+
+`timer` is set to 0, and the `while` loop’s condition is checking if `timer` is less than or equal to 5.
+0 is less than 5, so the code enters the while loop.
+Now the `if` statement checks whether `timer` is less than 5.
+0 is less than 5, so it prints out `Drive Forward`.
+The `if` statement is done, and the code runs `timer++`, which increases `timer`’s value by one.
+
+The code goes back to the `while` loop.
+1 is less than 5, so the code enters the `while` loop again.
+For the `if` statement, 1 is less than 5.
+Therefore, `Drive Forward` gets printed out again.
+
+This repeats 4 times until `timer` is 5.
+Once this happens, the `if` statement is skipped since 5 is not less than 5.
+Now the else runs and prints out `Stop Driving`, `timer`’s value increases to 6, 6 is not less than 5, so the code stops running.
+
+## for
+
+With the power of while loops, we're able to repeat a block of code any number of times, like so:
+
+```java #ForExample1
+
+```
+
+This loop depends on 3 important statements:
+`int i = 0;`, `i < 6`, and `i++`.
+For loops allow us to inline these statements:
+
+```java #ForExample2
+
+```
+
+Using the previous, we can see that the `for` loop syntax includes:
+
+- the `for` keyword to declare that we're making a `for` loop
+- `()`to hold the three statements which allow the loop to run
+- `{` to denote the opening of the loop's code block
+- `}` to denote the ending of the loop's code block
+
+The three statements are
+
+- **initialization**: creates a variable that sets the starting point of the loop.
+  This is the `int i = 0;` seen in the previous example.
+- **condition**: a condition, which uses the variable, that is checked before each iteration.
+  This is `i < 6;`.
+  If the condition is true, the code inside the loop runs
+- **update**: updates the variable created in initialization after each iteration.
+  Lastly, that's `i++`;
+
+All 3 statements are optional, but the semicolons must be present.
+However, the examples in this section will use all statements.
+
+Let's look at another example:
+
+```java #forExample
+
+```
+
+In this example, we create a variable `i` that is set to 0. When `i` is less than 5, the `for` code block runs, printing the value of `i` which is 0.
+Then it goes back to the update statement which is `i++`, `i` has increased by 1 and `i`'s value is now 1.
+We check the condition, 1 is less than 5, so `for` code block runs, the new value of `i` is printed, `i` is updated and this repeats until `i` is no longer less than 5.
+When `i` is no longer less than 5, the `for` loop is skipped.
+
+## Be Careful about Infinite Loops
+
+It is important to make sure that the condition can become false.
+If the condition is always true, the loop will always run causing an infinite loop.
+When an infinite loop happens, the code never stops.
+This can be unsafe if the code is running a robot mechanism.
+This could cause a robot to never stop driving forward or an arm to always move.
+Infinite loops can be prevented by ensuring that the value inside the condition changes by incrementing or decrementing.
+
+<Aside type="note">
+
+When diving into FRC programming, you will find that infinite loops are occasionally encouraged (such as in commands).
+This will be talked about more in Stage 1
+
+</Aside>
+
+{/* rli:ignore */}
+
+```java
+    int timer = 0;
+    if (false) {
+        while (timer < 7){
+            drivetrain.setThrottle(1); // sets drive motors to full speed
+        }
+    }
+```
+
+In this example, we want our drive train to run for 7 seconds.
+We have our variable called `timer` which is set to 0.
+0 is less than 7 so the code inside runs and the robot drives forward at full speed.
+However, `timer`'s value never changes.
+This means `timer` will always be 0. 0 is less than 7 so the loop will continuously run and the robot never stops driving!
+
+To fix this, we would make sure to increment the timer value as shown below.
+
+{/* rli:ignore */}
+
+```java
+    int timer = 0;
+    while (timer < 7){
+        drivetrain.setThrottle(1); // sets drive motors to full speed
+        timer++; // increments timer by 1
+    }
+```
+
+`timer` now increments by 1 each time the loop is run, and the robot will stop driving after 7 seconds.
+
+## Loops Exercise
+
+<Aside type="exercise">
+
+WIP
+
+</Aside>