Can anybody point out why my field is throwing errors?

I'm currently working on a small project to improve my Java skills and settled on a small project which tests your ability to design and implement Java classes to model and manipulate data.
I have to create classes to manage a collection of vehicle hire bookings for a vehicle-hire company. I have to develop classes using an inheritance hierarchy, and appropriate collection types from the Java Collections Framework (JCF).

So far I've created my first class which is the Vehicle class which models a vehicle for hire, and a second class which models the hiring of a vehicle.

I'm having a bit of trouble making my classes talk to each other and was hoping somebody could point me in the right direction. My vehicle class is fine and has no errors, the problem is on the hire class where I don't seem to be able to get my 'Vehicle' field to function properly. Below is the code for my two classes.

Thanks a lot in advance for any help

//Import the comparator 
import java.util.Comparator;
//Task 1 - Vehicle Class
public class Vehicle {
//Private string field that stores the name of the vehicle
//Private double field that stores the cost per day for vehicle hire
private String modelName;
private double dailyCost;
//Constructor for vehicle with two fields using two parameters
public Vehicle(String Modelname, double dailyCost) {
this.modelName = modelName;
this.dailyCost = dailyCost;
}
//Getter for model name
public String getModelname() {
return modelName;
}
//Setter for model name
public void setModelName() {
this.modelName = modelName;
}
//Getter for daily cost
public double getDailyCost() {
return dailyCost;
}
//Setter for daily cost
public void setDailyCost() {
this.dailyCost = dailyCost;
}
@Override
//Return details as formatted String 
public String toString(){
String result = "Vehicle: " + this.getModelname()+ " £" + this.getDailyCost() + " per day\n";
return result;
}
}
//Task 2 - Abstract Hire class
public abstract class Hire {
//Private field of type vehicle to store the vehicle on hire
//Private int to store the duration of hire in days 
private int days;
//Need to declare this field properly later 
private Vehicle aVehicle = new Vehicle(String modelName, double dailyCost);
//Constructor for the Hire with two fields and two parameters
public Hire(String vehicle, int days) {
this.vehicle = vehicle;
this.days = days;
}
//Getter for model days
public int getDays() {
return days;
}
//Setter for model days
public void setdays() {
this.days = days;
}
//Getter for model vehicle
public String getVehicle() {
return vehicle;
}
//Setter for model vehicle
public void setVehicle() {
this.vehicle = vehicle;
}
//Method to calculate the total cost of hire 
public double getCost(){
return (days * dailyCost);
}
//Think this is in the right place?
@Override
//Method to return the details of Hire as a string 
public String toString(){
String result = ("Vehicle: " + this.modelName()+ this.dailyCost + " per day. Days: " + this.getDays + " Hire Cost: " + this.getCost );
return result;
}
}

You need to pass to the Vehicle constructor inside Hire actual values
for example:

new Vehicle("Toyota", 100);

I use Lambda to create a instace Object hire to extend abstract class Hire and over-write setter/getter method.Now it works.

Hire Class:

public abstract class Hire {
    //Private field of type vehicle to store the vehicle on hire
    //Private int to store the duration of hire in days
    private int days;
    private String vehicle;

    private int dailyCost;
    //Need to declare this field properly later
    private Vehicle aVehicle;

    // a blank Constructor
    public Hire(){

    }

    //Constructor for the Hire with two fields and two parameters
    public Hire(String vehicle, int days) {
        this.vehicle = aVehicle.getModelname();
        this.days = days;
    }

    //Getter for model days
    public int getDays() {
        return days;
    }

    //Setter for model days
    public void setdays() {
        this.days = days;
    }

    //Getter for model vehicle
    public String getVehicle() {
        return vehicle;
    }

    //Setter for model vehicle
    public void setVehicle(Vehicle vehicle) {
        this.vehicle = vehicle.getModelname();
    }

    //Method to calculate the total cost of hire
    public double getCost(){
        return (days * dailyCost);
    }


    //Think this is in the right place?
    @Override
    //Method to return the details of Hire as a string
    public String toString(){
        String result = ("Vehicle: " + this.aVehicle.getModelname()+ this.dailyCost + " per day. Days: " + this.getDays() + " Hire Cost: " + this.getCost() );
        return result;
    }
}

Test Class:

public class Test {
    public static void main(String[] args){
        Vehicle vehicle = new Vehicle("Driver",100);
        Hire hire = new Hire() {
            @Override
            public int getDays() {
                return super.getDays();
            }

            @Override
            public void setVehicle(Vehicle vehicle) {
                super.setVehicle(vehicle);
            }

            @Override
            public String getVehicle() {
                return super.getVehicle();
            }
        };

        hire.setVehicle(vehicle);
        System.out.println("Vehivle Class Name: " + vehicle.getModelname());

        System.out.println("Abstract Hire Class Name: " + hire.getVehicle());
    }
}

The output is :

Vehivle Class Name: Driver
Abstract Hire Class Name: Driver

As @tobias-k said: new Vehicle(String modelName, double dailyCost); is not valid. You can pass Vehicle instance by Hire constructor<br>

private Vehicle vehicle;
public Hire(Vehicle vehicle, int days) {
this.vehicle = vehicle;
this.days = days;
}

Additionaly I fixed those methods:

public Vehicle getVehicle() { //Valid return type
return vehicle;
}
public void setVehicle(Vehicle vehicle) { //Pass vehicle instance to set as this.vehicle value
this.vehicle = vehicle;
}
public void setdays(int days) { //Pass int valueto set as this.days value
this.days = days;
}
public double getCost(){
return (days * this.vehicle.getDailyCost()); //Valid get dailyCost via Vehicle getter
}
@Override
public String toString() { //Accesses via getters and formatted
return "Vehicle: " + this.vehicle.getModelname() + this.vehicle.getDailyCost() +
" per day. Days: " + this.days + " Hire Cost: " + this.getCost();
}

Fixes for Vehicle class:
<br>

1. (modelName typo)

instead of :

public Vehicle(String Modelname, double dailyCost) {
this.modelName = modelName;
this.dailyCost = dailyCost;
}

use:

public Vehicle(String modelName, double dailyCost) {
this.modelName = modelName;
this.dailyCost = dailyCost;
}

<br>
2. (lack of String modelName)

instead of :

public void setModelName() {
this.modelName = modelName;
}

use :

public void setModelName(String modelName) {
this.modelName = modelName;
}

<br>
3. (lack of double dailyCost)

instead of :

public void setDailyCost() {
this.dailyCost = dailyCost;
}

use:

public void setDailyCost(double dailyCost) {
this.dailyCost = dailyCost;
}

Try change:

• private Vehicle aVehicle = new Vehicle(String modelName, double dailyCost); with private Vehicle aVehicle = new Vehicle("", (Double) 0); or null because you need to instanciate something, and not pass the contructor;

• public Hire(String vehicle, int days) { with public Hire(Vehicle vehicle, int days) { because you need a Vehicle class and not a String;

• this.vehicle = vehicle; to this.aVehicle = vehicle; because aVehicle is the name of variable in Hire class.

First of all your constructor at 'Vehicule' class is wrong

public Vehicle(String Modelname, double dailyCost) {
this.modelName = modelName;
this.dailyCost = dailyCost;
}

The parameter 'String Modelname' is written with a capital M, but the 'modelname' you're giving to 'this.modelname' is actually the class property,
it's like you're doing : this.modelName=this.modelName
Which means you're adding nothing new to it

Secondly, why would your 'Hire' class be abstract if you're willing to use it ? an abstract class can't be initialized.

I also found two main errors in this class :

1. private Vehicle aVehicle = new Vehicle(String modelName, double dailyCost);
   Here you must first declare the String 'modelname' and double 'dailyCost' and give them a value before creating your aVehicle object.

-Or just do this instead : Vehicle aVehicle = new Vehicle("Volkswagen",42069);

2. your getters and setters for Vehicule are wrong because you declared your Vehicle property as aVehicle with an 'a' and not 'vehicule'

Your getters and setters should be like this instead :

 public String getaVehicle() {
return aVehicle;
}
//Setter for model vehicle
public void setaVehicle(Vehicle aVehicle) {
this.aVehicle = aVehicle;
}

Finally, your toString method in this class is wrong because of the same initiale error, you didn't declare the modelName and dailycost properties in your Hire class.
Now if you want a inheritance between the two classes, you should do this :

public class Hire extends Vehicle {
...
}

This inheritance means that your child class 'Hire' class will 'inherite' all the attributes and methods from your parent class Vehicle class, so you won't have to declare the modelname and dailycost attributes in Hire class again, because they are already present in your Vehicle class.