Enums

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Enums (Enumerations)

What is an Enum?

An enum (short for enumeration) is a special Java type used to define a collection of named constants. Enums are used when you have a fixed set of related values that a variable can hold, making your code more readable and less error-prone.

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Why Use Enums?

• Readability: Instead of using arbitrary numbers or strings to represent states or modes, enums give meaningful names.

• Type Safety: Enums restrict values to a predefined set, preventing invalid assignments.

• Maintainability: If you need to add or modify states, you update the enum in one place.

• Better Code Structure: Enums can have methods and fields, allowing richer behavior.

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Simple Example

Suppose you have a shooter subsystem with different states:

public enum ShooterState {
    IDLE,
    SPINNING_UP,
    SHOOTING,
    COOLING_DOWN
}

You can now use this enum to represent the current state:

ShooterState currentState = ShooterState.IDLE;

if (currentState == ShooterState.SPINNING_UP) {
    // Run motors to spin up the shooter
}

This is much clearer than using integers like 0, 1, 2, or strings like "idle" which are prone to typos.

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Enums with Data and Methods

Enums can also have variables, constructors, and methods. For example:

public enum ShooterState {
    IDLE(0),
    SPINNING_UP(5000),  // RPM target
    SHOOTING(6000),
    COOLING_DOWN(0);

    private final int targetRPM;

    ShooterState(int rpm) {
        this.targetRPM = rpm;
    }

    public int getTargetRPM() {
        return targetRPM;
    }
}

You can then access the associated value:

int rpm = ShooterState.SPINNING_UP.getTargetRPM();  // rpm = 5000

This allows your enum to not only represent a state but also store related parameters.

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Enums in Subsystem State Machines

Enums are ideal to manage subsystem states clearly and reliably. For example, an intake roller subsystem might have:

public enum IntakeRollerState {
    OFF,
    INTAKING,
    EXHAUSTING
}

Your code can then switch behavior based on the state, like:

switch (currentState) {
    case OFF:
        stopMotors();
        break;
    case INTAKING:
        runIntakeMotors();
        break;
    case EXHAUSTING:
        reverseIntakeMotors();
        break;
}

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Summary

• Enums represent a fixed set of related constants.

• They improve code readability, safety, and maintainability.

• Can store associated data and methods.

• Perfect for managing states and modes in robot code.