Trying to use polymorphism, need some corrections

Question

So I am using the superclass Vehicle and subclass Van. The Van subclass inherits horsepower, weight, and aerodynamics from the superclass. I have also defined a new instance variable in Van called carryweight. When I try to run TestAcceleration.java I get this error:

java error

Here is the code:

VEHICLE SUPERCLASS

public class Vehicle
{
public double horsepower;
public double aerodynamics;
public double weight;

public Vehicle(double hp, double w, double ad)
{
    horsepower = hp;
weight = w; 
aerodynamics = ad;
}

public double getHorsepower()
{
    return horsepower;
}

public double getAerodynamics()
{
    return aerodynamics;
}

public double getWeight()
{
    return weight;
}

public double acceleration()
{
double calcAccel = (100/horsepower)*aerodynamics*weight/100;
double roundAccel = Math.round(calcAccel * 100.0) / 100.0;
return roundAccel;
}
}

VAN SUBCLASS

public class Van extends Vehicle
{
public double carryweight;

public Van(double hp, double w, double ad, double cw)
{
super(hp, w, ad, cw);
carryweight = cw;
}

public double getCarryweight()
{
    return carryweight;
}

public double acceleration()
{
double calcAccel = (100/horsepower)*(aerodynamics/2)*weight/100;
double roundAccel = Math.round(calcAccel * 100.0) / 100.0;
return roundAccel;
}
}

TESTACCELERATION CLASS

public class TestAcceleration
{
public static void main (String[] args)
{

Vehicle car1 = new Van(100, 3500, 0.9, 160.4);

System.out.println(car1.acceleration());

}
}

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Your parameters don't match, you probably meant `super(hp, w, ad);` . — Arnaud, Feb 05 '18 at 13:01
Your code shouldn't even compile, as no constructor with 4 arguments is to be found in the `Vehicule` class — DamCx, Feb 05 '18 at 13:03
Please understand that this community is not programming school where tutors help you with super basic problems. The idea is that do **serious** research prior posting questions. But it seems you didn't do that. You dont even understand that you have a **compiler** error. You are **not** running your classes. The screen shot (which you should not have used - as error messages are **text** and should be coming as **text** in your question) **clearly** tells you that the different parts of your source code simply dont "match up". — GhostCat, Feb 05 '18 at 13:05
@Tom No, actually he claims that he gets this error when *running* stuff. Unfortunately this newbie is still at a level where is not able to even correctly communicate his problem. — GhostCat, Feb 05 '18 at 13:08
@GhostCat And when people would actually look that the linked picture, they would see that OP is "running" the compiler to compile TestAcceleration.java. — Tom, Feb 05 '18 at 13:09
@Tom Pretty often, people here think that linking to a screen shot of *text* is a nogo anyway. So they most often will not follow that link, but click that "down arrow" icon instead ;-) — GhostCat, Feb 05 '18 at 13:24
@GhostCat That's fine, but one shouldn't claim what OP should actually get, then they don't even know that OP is currently asking about. — Tom, Feb 05 '18 at 13:46

score 2 · Answer 1 · answered Feb 05 '18 at 13:01

The super you are calling in the subclass calls the constructor of your parent class, in this case Vehicle so you must use the paremeters of it's constructor which are 3 and not 4 as you typed.

Parent class constructor

public Vehicle(double hp, double w, double ad)

Your code:

public Van(double hp, double w, double ad, double cw)
{
    super(hp, w, ad, cw); // this is wrong, you should call with only 3 parameters, there is no CW in your parent class. The call should be super(hp, w, ad);
    carryweight = cw;
}

score 0 · Answer 2 · answered Feb 05 '18 at 13:01

0

You have passed four arguments to Vehicle constructor in Van subclass.

super(hp, w, ad, cw);

Just remove cw from constructor and it will be ok.

answered Feb 05 '18 at 13:01

Hani

21
4

score 0 · Answer 3 · answered Feb 05 '18 at 13:02

0

In the constructor of your subclass you call:

super(hp, w, ad, cw);

But the constructor of your superclass has only three arguments. Remove the last argument and your code will compile.

answered Feb 05 '18 at 13:02

erdeanmich

33
3

Trying to use polymorphism, need some corrections

3 Answers3