Lesson 3.3: Using boolean Values for On-or-Off Robot State

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Technical Context

Sensors like Touch Sensors or Limit Switches only have two states: pressed or not pressed. Using boolean flags to store these states allows the robot to make binary decisions, such as stopping a lift before it hits a physical hard-stop and causes mechanical failure.

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How boolean Values Simplify Robot Decisions

A boolean is a primitive datatype that can only hold one of two values: true or false. In the FTC environment, digital sensors and gamepad buttons are inherently boolean. When you call getState() on a DigitalChannel (like a touch sensor), the SDK returns a boolean. Storing this result in a variable allows you to "capture" the state at a specific moment in the loop() cycle and use it for logic comparisons.

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Annotated Code

@TeleOp(name="Boolean_Logic")
public class BooleanLogic extends OpMode {

    // Declaring a boolean to track if the safety limit is reached
    boolean isAtLimit;
    DcMotor lift;
    DigitalChannel touch;

    @Override
    public void init() {
        lift  = hardwareMap.get(DcMotor.class, "lift");
        touch = hardwareMap.get(DigitalChannel.class, "limit_switch");
    }

    @Override
    public void loop() {
        // Capturing the current hardware state into the boolean variable
        isAtLimit = touch.getState();
        telemetry.addData("Safe to move?", isAtLimit);
    }
}

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Fill-in-the-Blank Practice

1. A variable type that can only represent two possible states is a/an __________.
2. The default value of a boolean variable in Java, if not assigned, is __________.
3. To invert a boolean value (changing true to false), we use the __________ operator.

Show answers

1. boolean
2. false
3. ! (the logical NOT operator)

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Simulator Challenge

Robot Scenario: Capture the state of the "A" button on gamepad1 into a boolean variable and send that variable to the Driver Station via telemetry.

1.Complete the codeWork in fullscreen when you need more room for the editor and visualizer.

2.Run the lifecyclePress Init, then Start. Use the available gamepad or scene controls.

3.Debug the behaviorCheck telemetry, motion, requirements, and hints before opening the answer.

Telemark Unit 3 Simulator

Tracks `String`, `double`, `boolean`, and `int` variables as you edit.

Supports telemetry, `gamepad1`, simple `if` blocks, and basic `setPower()` math.

Does not simulate full hardware behavior or complex Java control flow.

Show answer

@Override
public void loop() {
    boolean buttonState = gamepad1.a;
    telemetry.addData("Button A Pressed", buttonState);
}

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