Question

Create a data class named Automobile that implements the Comparable interface. Give the class data fields for make, model, year, and price. Then add a constructor, all getters, a toString method that shows all attribute values, and implement Comparable by using the year as the criterion for comparing instances.

Write a program named TestAutos that creates an ArrayList of five or six Automobiles. Use a for loop to display the elements in the ArrayList. Sort the Arraylist of autos by year with Collections.sort(). Finally, use a foreach loop to display the ArrayList sorted by year.

Answer 1

Automobile.java

public class Automobile implements Comparable<Automobile>{
  
   String make;
   String model;
   int year;
   int price;
  
   public Automobile(String make, String model, int year, int price) {
       super();
       this.make = make;
       this.model = model;
       this.year = year;
       this.price = price;
   }

   public String getMake() {
       return make;
   }

   public String getModel() {
       return model;
   }

   public int getYear() {
       return year;
   }

   public int getPrice() {
       return price;
   }

   @Override
   public String toString() {
       return "Automobile [make=" + make + ", model=" + model + ", year=" + year + ", price=" + price + "]";
   }

   @Override
   public int compareTo(Automobile o) {
       // TODO Auto-generated method stub
       return this.year - o.year;
   }
}

TestAutos.java

import java.util.ArrayList;
import java.util.Collections;
import java.util.List;

public class TestAutos {
  
   public static void main(String[] args) {
       List<Automobile> automobiles = new ArrayList<>();
       automobiles.add(new Automobile("A", "abc", 1900, 25000));
       automobiles.add(new Automobile("B", "asq", 1910, 4000));
       automobiles.add(new Automobile("C", "kve", 1820, 5100));
       automobiles.add(new Automobile("D", "cmw", 1816, 9400));
       automobiles.add(new Automobile("E", "vrw", 1960, 20000));
       automobiles.add(new Automobile("F", "jeq", 1905, 6500));
       System.out.println("Before sorting: ");
       for(int i=0;i<automobiles.size();i++)
           System.out.println(automobiles.get(i));
       Collections.sort(automobiles); // sort on basis of year
       System.out.println("After sorting: ");
       for(Automobile automobile : automobiles)
           System.out.println(automobile);
   }

}

OUTPUT :

Before sorting: Automobile (make=A, model=abc, year=1900, price=25000] Automobile (make=B, model=asq, year=1910, price=4000] Automobile (make=C, model=kve, year=1820, price=5100] Automobile (make=D, model=cmw, year=1816, price=9400] Automobile [make-E, model=vrw, year=1960, price=20000] Automobile (make=F, model=jeq, year=1905, price=6500] After sorting: Automobile (make=D, model=cmw, year=1816, price=9400] Automobile [make=C, model=kve, year=1820, price=5100] Automobile (make=A, model=abc, year=1900, price=25000] Automobile (make=F, model=jeq, year=1905, price=6500] Automobile (make=B, model=asq, year=1910, price=4000] Automobile (make=E, model=vrw, year=1960, price=20000]