Question

This assignment involves writing a program that uses an abstract class and concrete subclasses. An abstract Vehicle class declares an abstract method named display() that is used to display vehicles. Vehicle has two subclasses: Boat and Car. A Boat has a length attribute, and a draft attribute (a draft is how far below the surface the bottom of the boat is). A Car has a make attribute and a year attribute. Appropriate getter, setter, and constructor methods should be defined for the subclasses, as well as an implementation of the display() method. All the method needs to do is to display the type of object and its attributes. Develop a class that has a main method that creates an array of type Vehicle, and populates it with a few Boat and Car objects. Prompt the user to enter attributes for the objects, and then use a looping construct to iterate through the array and display object attributes and invoke the display() method.

Answer 1

import java.util.*;

abstract class Vehicle // base class
{
  
   abstract void display();
  
}
class Boat extends Vehicle // derived class
{
   private int length,draft;
  
   public Boat() // default constructor
   {
       length = 0;
       draft = 0;
   }
   public Boat(int length,int draft)// argument constructor
   {
       this.length = length;
       this.draft = draft;
   }
   public void display()
   {
       System.out.println("Boat length : "+length+" draft : "+draft);
      
   }
   //set and get methods
   public void setLength(int length)
   {
       this.length = length;
   }
   public void setDraft(int draft)
   {
       this.draft = draft;
   }
   public int getLength()
   {
       return length;
   }
   public int getDraft()
   {
       return draft;
   }
  
}

class Car extends Vehicle
{
   private String make;
   private int year;
  
   public Car()
   {
       make = "";
       year = 0;
   }
   public Car(String make,int year)
   {
       this.make = make;
       this.year = year;
   }
   public void display()
   {
       System.out.println("Car make : "+make +" year : "+ year);
      
   }
   public void setMake(String make)
   {
       this.make = make;
   }
   public void setYear(int year)
   {
       this.year = year;
   }
   public String getMake()
   {
       return make;
   }
   public int getYear()
   {
       return year;
   }
  
}
class TestVehicles
{
   public static void main (String[] args)
   {
       Vehicle[] v = new Vehicle[5]; // array of Vehicle objects
       Scanner input = new Scanner(System.in);
      
       Boat b = new Boat();
       System.out.println("Enter the length and draft of the boat : ");
       int length = input.nextInt();
       int draft = input.nextInt();
       b.setLength(length);
       b.setDraft(draft);
      
       v[0] = b;
      
       Car c = new Car();
       System.out.println("Enter the make and year of the car : ");
       String make = input.next();
       int year = input.nextInt();
       c.setMake(make);
       c.setYear(year);
      
       v[1] = c;
      
      
       for(int i=0;i<=1;i++)
       {
           v[i].display();
       }
      
      
   }
}

Output:

Enter the length and draft of the boat : 34 5
Enter the make and year of the car : Ford 2017
Boat  length : 34 draft : 5
Car make : Ford year : 2017

Do ask if any doubt. Please upvote.