Question

QUESTION 5 (15 Marks) Inheritance and Polymorphism Design a Ship class that has the following members: • A private String data field named name for the name of the ship. • A private String data field named yearBuilt for the year that the ship was built. • A constructor that creates a ship with the specified name and the specified year that the ship was built. • Appropriate getter and setter methods. A toString method that overrides the toString method in the Object class and returns a string containing the class name Ship, the ship's name and the year it was built. Use @Override to ensure you override the method. Design a CruiseShip class that extends the Ship class. The CruiseShip class should have the following members: • A private int data field named passengerCapacity for the maximum number of passengers. • A constructor that creates a cruise ship with the specified name, the specified year that the ship was built, and the specified passenger capacity. • Appropriate getter and setter methods. • A toString method that overrides the toString method in the base class and returns a string containing the class name CruiseShip, the ship's name and passenger capacity. Use @Override to ensure you override the method. Design a CargoShip class that extends the Ship class. The CargoShip class should have the following members: • A private int data field named tonnage for the cargo capacity.

Answer 1

Ship.java

/** Definition of Ship class */
public class Ship
{
/** private member variables of Ship class */
private String name;
private String yearBuilt;

/** Constructor to initialize the member variables */
public Ship(String na, String year)
{
name = na;
yearBuilt = year;
}
  
/** Setter methods for the private member variables */
public void setName(String na)
{
name = na;
}
  
public void setYearBuilt(String year)
{
yearBuilt = year;
}
  
/** Getter methods for the private member variables */
public String getName()
{
return name;
}
  
public String getYearBuilt()
{
return yearBuilt;
}
  
/** toString method of Object class is overridden to return a string
* with the details of the Ship
*/
@Override
public String toString()
{
String s="";
s = "Ship \n";
s = s + "Name: " + getName() + "\n";
s = s + "Year Built: " + getYearBuilt() + "\n";
return s;
}
}

/** Definition of Ship class */ public class Ship /** private member variables of Ship class */ private String name; private String yearBuilt; /** Constructor to initialize the member variables / public Ship (String na, String year) name = na; yearBuilt = year; /** Setter methods for the private member variables / public void setName (String na) name = na; public void setYearBuilt (String year) yearBuilt = year; /** Getter methods for the private member variables / public String getName() return name;

public String getYearBuilt() return yearBuilt; /** toString method of Object class is overridden to return a string * with the details of the Ship */ @Override public String toString() String s=""; 8 = "Ship \n"; 8 = 3 + "Name:" + getName() + "\n"; 8 = + "Year Built: " + getYearBuilt() + "\n"; return s;

=======================================================================================

CargoShip.java

/** Definition of subclass CargoShip from superclass Ship */
public class CargoShip extends Ship
{
/** private member variable of CargoShip class */
private int tonnage;

/** Constructor to initialize the member variables of subclass */
public CargoShip(String na, String year, int weight)
{
/** super() keyword is used to call the constructor of
* the superclass before initializing the member variables of
* subclass
*/
super(na,year);
tonnage = weight;
}
  
/** Setter and getter */
public void setTonnage(int weight)
{
tonnage = weight;
}
  
public int getTonnage()
{
return tonnage;
}

/** The toString() method of superclass Ship is overridden by the subclass */
@Override
public String toString()
{
String s="";
s = "CargoShip \n";
s = s + "Name: " + getName() + "\n";
s = s + "Cargo Capacity: " + getTonnage() + " tons\n";
return s;
}
}

/ ** Definition of subclass CargoShip from superclass Ship public class CargoShip extends Ship /** private member variable of CargoShip class */ private int tonnage; /** Constructor to initialize the member variables of subclass / public CargoShip (String na, String year, int weight) /** super() keyword is used to call the constructor of * the superclass before initializing the member variables of * subclass super (na, year); tonnage = weight; /** Setter and getter */ public void setTonnage (int weight) tonnage = weight; public int getTonnage) return tonnage;

/** The toString() method of superclass Ship is overridden by the subclass */ @Override public String toString() String s=""; 3 = "CargoShip \n"; 3 = 3 + "Name: " + getName() + "\n"; 3 = 8 + "Cargo Capacity: " + getTonnage () + " tons\n"; return s;

=======================================================================================

CruiseShip.java

/** Definition of subclass CruiseShip from superclass Ship */
public class CruiseShip extends Ship
{
/** private member variable of CruiseShip class */
private int passengerCapacity;

/** Constructor to initialize the member variables of subclass */
public CruiseShip(String na, String year, int capacity)
{
/** super() keyword is used to call the constructor of
* the superclass before initializing the member variables of
* subclass
*/
super(na,year);
passengerCapacity = capacity;
}
  
/** Setter and getter */
public void setPassengerCapacity(int capacity)
{
passengerCapacity = capacity;
}
  
public int getPassengerCapacity()
{
return passengerCapacity;
}

/** The toString() method of superclass Ship is overridden by the subclass */
@Override
public String toString()
{
String s="";
s = "CruiseShip \n";
s = s + "Name: " + getName() + "\n";
s = s + "Passenger Capacity: " + getPassengerCapacity() + " persons\n";
return s;
}
}

/** Definition of subclass CruiseShip from superclass Ship */ public class Cruise Ship extends Ship /** private member variable of CruiseShip class */ private int passengerCapacity: /** Constructor to initialize the member variables of subclass / public Cruise Ship (String na, String year, int capacity) /** super() keyword is used to call the constructor of * the superclass before initializing the member variables of * subclass super (na, year); passengerCapacity = capacity; /** Setter and getter */ public void setPassengerCapacity (int capacity) passengerCapacity = capacity; public int get PassengerCapacity) return passengerCapacity:

/** The toString() method of superclass Ship is overridden by the subclass */ @Override public String toString() String s=""; 3 = "CruiseShip \n"; 3 = 3 + "Name: " + getName() + "\n"; 3 = 3 + "Passenger Capacity: " + getPassengerCapacity () + " persons\n"; return 3;

===================================================================================

TestShips.java

/** Test Class */
public class TestShips
{
/** Driver method to create objects of all three ships
* and print their details
*/
public static void main(String[] args)
{
/** Create an array of type Ship, to hold Ship objects */
Ship ShipArray[] = new Ship[3];

/** Create an object of super class Ship */
Ship ship1 = new Ship("Lolipop","1960");
/** Create an object of subclass CruiseShip and assign the object
to Ship reference variable */
Ship ship2 = new CruiseShip("Disney Magic","1960",2400);
/** Create an object of subclass CargoShip and assign the object
to Ship reference variable */
Ship ship3 = new CargoShip("Black Pearl","1960",50000);
  
/** Store all three objects in the array */
ShipArray[0] = ship1;
ShipArray[1] = ship2;
ShipArray[2] = ship3;
  
/** Loop through the array to print all ships */
for(int i=0;i<ShipArray.length;i++)
{
System.out.println(ShipArray[i]);
System.out.println();
}
}
}

/** Test Class */ public class Test Ships /** Driver method to create objects of all three ships * and print their details */ public static void main(String[] args) /** Create an array of type Ship, to hold ship objects / Ship ShipArray[] = new Ship[3]; /** Create an object of super class Ship */ Ship shipl = new Ship ("Lolipop", "1960"); /** Create an object of subclass Cruise Ship and assign the object to Ship reference variable */ Ship ship2 = new Cruise Ship ("Disney Magic","1960", 2400); /** Create an object of subclass CargoShip and assign the object to Ship reference variable */ Ship ship3 - new CargoShip ("Black Pearl","1960", 50000); /** Store all three objects in the array */ ShipArray[0] = shipl; ShipArray[1] = ship2; ShipArray[2] = ship3; /** Loop through the array to print all ships */ for (int i=0;i<ShipArray.length;i++) System.out.println(ShipArray[i]); System.out.println();

========================================================================================

Output:

Ship Name: Lolipop Year Built: 1960 Cruise Ship Name: Disney Magic Passenger Capacity: 2400 persons CargoShip Name: Black Pearl Cargo Capacity: 50000 tons