Three Wheel With Multiplier.java

package org.firstinspires.ftc.teamcode.drive;

import androidx.annotation.NonNull;

import com.acmerobotics.dashboard.config.Config;
import com.acmerobotics.roadrunner.geometry.Pose2d;
import com.acmerobotics.roadrunner.localization.ThreeTrackingWheelLocalizer;
import com.qualcomm.robotcore.hardware.DcMotorEx;
import com.qualcomm.robotcore.hardware.HardwareMap;
import org.firstinspires.ftc.teamcode.util.Encoder;

import java.util.Arrays;
import java.util.List;

/*
 * Sample tracking wheel localizer implementation assuming the standard configuration:
 *
 *    /--------------\
 *    |     ____     |
 *    |     ----     |
 *    | ||        || |
 *    | ||        || |
 *    |              |
 *    |              |
 *    \--------------/
 *
 */
@Config
public class StandardTrackingWheelLocalizer extends ThreeTrackingWheelLocalizer {
    public static double TICKS_PER_REV = 0;
    public static double WHEEL_RADIUS = 2; // in
    public static double GEAR_RATIO = 1; // output (wheel) speed / input (encoder) speed

    public static double LATERAL_DISTANCE = 10; // in; distance between the left and right wheels
    public static double FORWARD_OFFSET = 4; // in; offset of the lateral wheel

    public static double X_MULTIPLIER = 1; // Multiplier in the X direction
    public static double Y_MULTIPLIER = 1; // Multiplier in the Y direction
  
    private Encoder leftEncoder, rightEncoder, frontEncoder;

    public StandardTrackingWheelLocalizer(HardwareMap hardwareMap) {
        super(Arrays.asList(
                new Pose2d(0, LATERAL_DISTANCE / 2, 0), // left
                new Pose2d(0, -LATERAL_DISTANCE / 2, 0), // right
                new Pose2d(FORWARD_OFFSET, 0, Math.toRadians(90)) // front
        ));

        leftEncoder = new Encoder(hardwareMap.get(DcMotorEx.class, "leftEncoder"));
        rightEncoder = new Encoder(hardwareMap.get(DcMotorEx.class, "rightEncoder"));
        frontEncoder = new Encoder(hardwareMap.get(DcMotorEx.class, "frontEncoder"));

        // TODO: reverse any encoders using Encoder.setDirection(Encoder.Direction.REVERSE)
    }

    public static double encoderTicksToInches(int ticks) {
        return WHEEL_RADIUS * 2 * Math.PI * GEAR_RATIO * ticks / TICKS_PER_REV;
    }

    @NonNull
    @Override
    public List<Double> getWheelPositions() {
        return Arrays.asList(
                encoderTicksToInches(leftEncoder.getCurrentPosition()) * X_MULTIPLIER,
                encoderTicksToInches(rightEncoder.getCurrentPosition()) * X_MULTIPLIER,
                encoderTicksToInches(frontEncoder.getCurrentPosition()) * Y_MULTIPLIER
        );
    }
    
    
    @NonNull
    @Override
    public List<Double> getWheelVelocities() {
        // TODO: If your encoder velocity can exceed 32767 counts / second (such as the REV Through Bore and other
        //  competing magnetic encoders), change Encoder.getRawVelocity() to Encoder.getCorrectedVelocity() to enable a
        //  compensation method

        
        return Arrays.asList(
                encoderTicksToInches(leftEncoder.getRawVelocity()) * X_MULTIPLIER,
                encoderTicksToInches(rightEncoder.getRawVelocity()) * X_MULTIPLIER,
                encoderTicksToInches(frontEncoder.getRawVelocity()) * Y_MULTIPLIER
        );
    }
}

TICKS_PER_REV = 0; why is it 0 instead of 8192?

You are supposed to input with whatever value corresponds with your encoder specification. The Rev Encoder is 8192. However, this has not historically been the only encoder in use.
I do not know the current state of affairs and the Rev Encoder may be the default now.