Java While Loops → Java Break/Continue

Complete the W3Schools lessons from Java While Loop through Java Break/Continue.

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Robotics Programming Challenge: Intake Control

Objective

You are programming the intake mechanism of an FRC robot.

Your job is to write the code that controls two motors:

• Intake motor — pulls game pieces into the robot
• Indexer motor — moves game pieces farther into the robot

The robot operator has several controls, and the intake has a sensor that detects when a game piece has been collected.

You will be given some starter code, but you are responsible for writing the majority of the control logic.

1. Starter Code

Begin with:

public class IntakeChallenge {
 
    public static void main(String[] args) {
 
        // Operator controls
        boolean intakeButton = true;
        boolean outtakeButton = false;
 
        // Intake sensor
        boolean hasPiece = false;
 
        // Motor speed from 0.0 to 1.0
        double motorSpeed = 0.75;
 
        // Motor outputs
        double intakeMotor = 0;
        double indexerMotor = 0;
 
        // Your code goes here
 
 
 
        // Print final motor outputs
        System.out.println("Intake Motor: " + intakeMotor);
        System.out.println("Indexer Motor: " + indexerMotor);
    }
}

The motor outputs work like this:

2. Program the Intake

When the operator presses the intake button, the intake should run forward.

If:

intakeButton == true

then:

• intakeMotor should equal motorSpeed
• indexerMotor should equal motorSpeed

If the button isn’t pressed, the motors should not run unless another command tells them to.

You’ll need to decide what conditional structure makes sense here.

Display the Motor Speed

After setting the motor outputs, print the motor speed as a percentage.

Use an explicit cast to convert the calculated percentage to an integer:

System.out.println("Motor Speed: " + (int)(motorSpeed * 100) + "%");

For example, if motorSpeed is 0.75, the output should be:

Motor Speed: 75%

Print this line whenever the intake or outtake button is pressed.

3. Program the Outtake

The robot also needs to be able to spit a game piece back out.

When:

outtakeButton == true

the motors should run backward.

For example:

intakeMotor = -motorSpeed;

The indexer should also run backward.

Important

What happens if both intakeButton and outtakeButton are pressed?

Your program should choose one behavior rather than trying to run the motors in both directions.

Decide which command should have priority and implement it using if, else if, and else.

3.5. Use a Switch Statement

In addition to your if, else if, and else statements, use a switch statement to determine the robot’s current operating mode.

Create an integer variable:

int operatingMode = 0;

Use the following modes:

Use a switch statement to print the current operating mode:

Mode: Idle
Mode: Intake
Mode: Outtake

You may determine the operating mode using the operator buttons.

This statement should be used somewhere in your completed program.

4. Add the Game-Piece Sensor

The intake has a sensor called:

boolean hasPiece = false;

This tells you whether the robot currently has a game piece.

If the robot detects a game piece while intaking:

• The indexer should stop
• The intake should continue running
• Print:

GAME PIECE DETECTED
INDEXER STOPPED

For example:

Intake Motor: 0.75
Indexer Motor: 0.0

Think carefully about the order of your conditions.

The sensor should be able to override the normal indexer behavior.

## 5. Add a Motor Safety Limit

Real robot code shouldn’t blindly trust its inputs.

Add a safety check so that motorSpeed can never cause the motor to run above 100%.

For example, if:

double motorSpeed = 1.25;

your program should prevent the motor from running at 125%.

Print:

WARNING: MOTOR SPEED LIMITED

and adjust the speed to the maximum allowed value.

Important: Motor speed must always be between 0.0 and 1.0.

• If motorSpeed is greater than 1.0, set it to 1.0.
• If motorSpeed is less than 0.0, set it to 0.0.
• Otherwise, leave it unchanged.

This safety check should happen before calculating motor outputs.

6. Simulate Collecting a Game Piece

Now use a loop to simulate the intake collecting a game piece.

Only run this simulation when the intake button is pressed and the robot does not already have a game piece.

Start with:

int distanceToPiece = 5;

The distance represents how many arbitrary units away the game piece is.

While the robot is intaking, decrease the distance:

Distance to piece: 5
Distance to piece: 4
Distance to piece: 3
Distance to piece: 2
Distance to piece: 1
Distance to piece: 0
GAME PIECE COLLECTED

You will need to:

• Create a loop
• Use a comparison
• Change the distance each iteration
• Stop the loop when the piece reaches the robot
• Print the distance each iteration

Test A should include the distance simulation output.

7. Test Your Code

Change the starter variables to test different situations.

Test A — Intake

boolean intakeButton = true;
boolean outtakeButton = false;
boolean hasPiece = false;
double motorSpeed = 0.75;

Expected:

Distance to piece: 5
Distance to piece: 4
Distance to piece: 3
Distance to piece: 2
Distance to piece: 1
Distance to piece: 0
GAME PIECE COLLECTED
Intake Motor: 0.75
Indexer Motor: 0.75
Motor Speed: 75%

Test B — Already Have a Piece

boolean intakeButton = true;
boolean outtakeButton = false;
boolean hasPiece = true;
double motorSpeed = 0.75;

Expected:

GAME PIECE DETECTED
INDEXER STOPPED
Intake Motor: 0.75
Indexer Motor: 0.0
Motor Speed: 75%

Test C — Outtake

boolean intakeButton = false;
boolean outtakeButton = true;
boolean hasPiece = true;
double motorSpeed = 0.50;

Expected:

Intake Motor: -0.5
Indexer Motor: -0.5
Motor Speed: 50%

Test D — Nothing Happening

boolean intakeButton = false;
boolean outtakeButton = false;
boolean hasPiece = false;
double motorSpeed = 0.75;

Expected:

Intake Motor: 0.0
Indexer Motor: 0.0

Test E — Motor Speed Limit

double motorSpeed = 1.25;

Expected:

WARNING: MOTOR SPEED LIMITED
Intake Motor: 1.0
Indexer Motor: 1.0
Motor Speed: 100%

Final Requirements

Your completed program must use:

• boolean
• int
• double
• if
• else if
• else
• switch
• A for or while loop
• Arithmetic operators
• Comparison operators
• An explicit cast
• Intake control
• Outtake control
• Game-piece detection
• Motor speed limiting

CONGRATULATIONS!

You have completed what I consider starter Java.

You know how to do a lot of cool things in a main method, and you have become good at taking apart challenges and completing them on your own.

Up next is more basic Java, but it is going to take you much further than anything you’re able to do right now.

Keep it up!

To complete this lesson

Paste all your code challenges, including the Intake Control challenge, into this lesson’s tab in your training doc. Code goes in as text, no screenshots.