CODEWITHSUNDEEP
java
Konstantina Papagiannopoulou
Konstantina Papagiannopoulou

Reputation: 213

Error message while using inheritance in java

I am new to inheritance in java and I have the folowing problem. My base class is Plane, its child class is PlaneComponent and PlaneComponent's child class is PassengerCompartment. My program consists of 11 classes, when I ignore the PassengerCompartment class everythig's right. But when I run the whole program I get this message: at Plane.<init>(Plane.java:14) at PlaneComponent.<init>(PlaneComponent.java:1) at PassengerCompartment.<init>(PassengerCompartment.java:11) which is printed repeatedly for so many times that I cannot see the top line of the error. The lines includes in error messages are the bold lines (here printed between ** **).

Plane:

import java.util.*;

public class Plane
{
int cap;
int pl;

public Plane()
{
    String desc = "Plane Description";
    String title = "Boeing 747";
    Random rand = new Random();
    cap = rand.nextInt(100) + 51;       //initialize cap with 50<value<100
    **PassengerCompartment a8 = new PassengerCompartment();**
    pl = cap / a8.cap2;                 // pl = sum of Passenger Compartments
    if (cap % a8.cap2 != 0)
    {
        pl = pl - (cap % a8.cap2) + 1;
    }
}
public boolean ready_check()
{
    CargoBay a6 = new CargoBay();
    a6.ready_check();
    for (int i = 0 ; i < 3 ; i++)
    {
        EquipmentCompartment a7 = new EquipmentCompartment();
        a7.ready_check();
    }
    for(int i = 0; i < pl; i++)
    {
        PassengerCompartment a8 = new PassengerCompartment();
        a8.ready_check();
    }
    System.out.println("Plane OK!");
    return true;
}
public void process(String e)
{
    if(e == "SecurityEmployee")
    {
        SecurityEmployee a14 = new SecurityEmployee();
        a14.workOn();
    }
    if(e == "MaintenanceEmployee")
    {
        MaintenanceEmployee a15 = new MaintenanceEmployee();
        a15.workOn();
    }
    if(e == "CleaningEmployee")
    {
        CleaningEmployee a16 = new CleaningEmployee();
        a16.workOn();
    }
}

public void values()
{
    System.out.println("Would you like more info about the plane's capacity? type Y or N");
    Scanner input = new Scanner(System.in);
    String inp = input.nextLine();
    while (!(inp.equals("Y")) && !(inp.equals("N")))
    {
        System.out.println("Wrong input, please type again");
        inp = input.nextLine();
    }
    if ( inp.equals("Y"))
    {
        PassengerCompartment a8 = new PassengerCompartment();
        System.out.println("Plane's capacity: " + cap);
        System.out.println("PassComp's capacity: " + a8.cap2);
        System.out.println("Number ofPassenger Compartments " + pl);
    }
}

}

PlaneComponent:

**public class PlaneComponent extends Plane**
{
public boolean ready_check()
{
    return true;
}

public void process(String desc)
{
    Employee.workOn(desc);
}
}

PassengerCompartment:

import java.util.*;

public class PassengerCompartment extends PlaneComponent
{
Random rand = new Random();
boolean inner = rand.nextBoolean();
int cap2;
String desc;

public PassengerCompartment()
**{**
    desc = "Passenger Compartment";
    cap2 = rand.nextInt(50) + 21;       //initialize cap with 20<value<50
}
public boolean ready_check()
{
    System.out.println(desc);
    if (super.ready_check() == true)
    {
        System.out.println("Passenger Compartment OK!");
        if (inner == true)
        {
            desc = "Inner Compartment";
            System.out.println(desc);
            if (super.ready_check() == true)
            {
                System.out.println("Inner Compartment OK!");
            }
        }
    }
    return true;
}
public void process(String desc)
{
    super.process(desc);
}
}

Upvotes: 1

Views: 94

Answers (2)

pczeus
pczeus

Reputation: 7867

Your issue is with your inheritance structure.

In Planes constructor, you create an instance of PassengerCompartment. PassengerCompartment extends PlaneCompartment. PlaneCompartment extends `Plane'. So, you are in a circle.

I don't think it makes sense for PlaneCompartment to extends Plane. What you have is a 'has-a' relationship. So, Plane has a PlaneCompartment but neither extends each other.

Upvotes: 0

Idos
Idos

Reputation: 15310

You have a circular-inheritance-kind-of-situation (which probably creates a StackOverflow exception):

You instantiate PassengerCompartment a8 = new PassengerCompartment(); in the constructor of Plane.

PassengerCompartment extends PlaneComponent, so the constructor of PlaneComponent is called implicitly (super()), which inherit from Plane. In Plane's constructor you have the mentioned instantiation of PassengerCompartment and so on... So I would strongly advise to not instantiate classes that inherit from your class in the constructor of said class.

I would recommend reading my Q/A on this very topic here.

Upvotes: 2

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