Lesson 6.4: Looping Through Hardware Arrays with for-each

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Technical Context

Complex robots often utilize four drivetrain motors or multiple identical sensors. Iterating through these components individually is inefficient; using a for..each loop with a hardware array allows the programmer to apply a single command (like BRAKE behavior) to every component simultaneously, reducing the risk of accidentally missing a port.

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Why for-each Loops Scale Better with More Hardware

A Java array is instantiated to hold a fixed number of SDK objects (e.g., DcMotor[] motors = new DcMotor[4]). The for..each syntax: for (Type variable : array): provides a shortcut to access every object in that array without managing an index integer, ensuring every connected component receives the instruction in a clean, readable block.

Two things to remember:

• Arrays in Java are zero-indexed: the first element is at index 0.
• The variable type declared in the for..each header must match the type stored in the array.

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Annotated Code

package org.firstinspires.ftc.teamcode;

import com.qualcomm.robotcore.eventloop.opmode.OpMode;
import com.qualcomm.robotcore.eventloop.opmode.TeleOp;
import com.qualcomm.robotcore.hardware.DcMotor;

@TeleOp(name="Array_Drive_Demo")
public class ArrayDriveDemo extends OpMode {

    // Array declaration: holds all four drivetrain motors
    DcMotor[] allMotors;

    private DcMotor leftFront, rightFront, leftBack, rightBack;

    @Override
    public void init() {
        leftFront  = hardwareMap.get(DcMotor.class, "left_front");
        rightFront = hardwareMap.get(DcMotor.class, "right_front");
        leftBack   = hardwareMap.get(DcMotor.class, "left_back");
        rightBack  = hardwareMap.get(DcMotor.class, "right_back");

        // Populate the array after mapping
        allMotors = new DcMotor[]{ leftFront, rightFront, leftBack, rightBack };

        // Apply BRAKE behavior to every motor in one loop
        for (DcMotor motor : allMotors) {
            motor.setZeroPowerBehavior(DcMotor.ZeroPowerBehavior.BRAKE);
        }
    }

    @Override
    public void loop() {
        // Stop all motors at once using the array
        for (DcMotor motor : allMotors) {
            motor.setPower(0.0);
        }
    }
}

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Fill-in-the-Blank Practice

1. To declare an array of DC motors, the syntax is DcMotor__________ motors;.
2. The index of the first element in any Java array is __________.
3. In a for..each loop, the variable type must __________ the type of the objects stored in the array.

Show answers

1. [] (e.g., DcMotor[] motors;)
2. 0
3. match

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Simulator Challenge

Use the simulator below to practice looping across an array of motors and applying the same configuration to every element.

1.Complete the codeWork in fullscreen when you need more room for the editor and visualizer. Where file tabs are available, hover over the tab strip and choose + to create a file or reuse saved code.

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 6 Simulator

Supports OpMode and LinearOpMode practice with lesson-specific starter code.

Includes loop stepping, runtime tracking, lifecycle controls, and live gamepad input.

Best for practicing loop structure, timers, and safe control flow patterns.

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