Stupid Car

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package bai3;

import java.util.ArrayList;
import java.util.Scanner;

/**
 *
 * @author pc
 */
public class Main {

    public static Car f3(ArrayList<SUV> cars)
    {
        for (int i = 0; i < cars.size(); ++i){
            for (int j = i + 1; j < cars.size(); ++j) {
                if (cars.indexOf(i).getTax() < cars.indexOf(j).getTax()) {
                    SUV temp = (SUV)cars.indexOf(i);
                    cars.indexOf(i) = cars.indexOf(j);
                    cars.indexOf(j) = temp;
                }
            }
        }
        if (cars.size() <= 1) return null;
        return cars.indexOf(1);
    }

    public static void main(String[] args)
    {
        int numcar = 0;
        Scanner scanner = new Scanner(System.in);
        String input;
        System.out.println("Enter the number of car:");
        input = scanner.nextLine();
        numcar = Integer.parseInt(input);
        ArrayList<SUV> cars = new ArrayList<>();
        for (int i = 0; i < numcar; i++) {
            SUV car = new SUV();
            System.out.println("Car serial number:");
            car.serialNumber =scanner.nextLine();
            System.out.println("Car price:");
            car.price = Float.parseFloat(scanner.nextLine());
            System.out.println("Car tax:");
            car.ptax = Float.parseFloat(scanner.nextLine());
            cars.add(car);
        }
        Car secondExpCar = f3(cars);
        System.out.println(secondExpCar.display());
    }

}