在java中创建类实例的问题

我试图制作一个“赛车模拟器”,在其中创建和比较车辆。它包括定义车辆的类别和比较其速度的主要类别。当我创建两个Vehicle实例并在两个实例上使用getSpeed方法时,速度是相同的。知道为什么吗?

主要:

public class Main {

    static Vehicle bike, jeep;
    //static Race race;

    public static void main(String args[]) {
        bike = new Vehicle(4000, 20, 30.5, "bike");
        jeep = new Vehicle(3000, 12, 9.8, "Jeep");
        //race = new Race(bike, jeep, 0);
        System.out.println("Bike: " + bike.getTopSpeed() + " Jeep: " + jeep.getTopSpeed());
    }
}

public class Vehicle {

    static int _weight, _topSpeed;
    static double _zeroToSixty;
    static String _vehicleName;

    public Vehicle(int weight, int topSpeed, double zeroToSixty, String vehicleName) {
        _weight = weight;
        _topSpeed = topSpeed;
        _zeroToSixty = zeroToSixty;
        _vehicleName = vehicleName;
    }

    public static void setVehicleName(String name) {
        _vehicleName = name;
    }

    public static void setWeight(int weight) {
        _weight = weight;
    }

    public static void setTopSpeed(int topSpeed) {
        _weight = topSpeed;
    }

    public static void setZeroToSixty(double zeroToSixty) {
        _zeroToSixty = zeroToSixty;
    }

    public static String getVehicleName() {
        return _vehicleName;
    }

    public static int getWeight() {
        return _weight;
    }

    public static int getTopSpeed() {
        return _topSpeed;
    }

    public static double getZeroToSixty() {
        return _zeroToSixty;
    }
}

main的输出为:

“自行车:12吉普车:12”