Question

Animal class

Create a simple class called Animal instantiated with a name and a method toString which returns the name.

Cat class

Create a simple class Cat which extends Animal, but adds no new instance variable or methods.

RedCat class

Create a simple class RedCat which extends Cat, but adds no new instance variable or methods.

WildCardTester class

Create a class with the main method and methods addCat, deleteCat and printAll as follows.

addCat method

Has two parameters, an ArrayList with a lower bound of RedCat, and a String with the name of a Cat. Adds the identified Cat reference to the ArrayList, and prints out a line as shown in the sample output below.

deleteCat method

Has two parameters, an ArrayList with an upper bound of Cat, and a String with the name of a Cat to be deleted. Deletes the identified Cat reference to the ArrayList, and prints out a line as shown in the sample output below.

printAll method

Has a single parameter of an ArrayList with a wildcard type. Prints out all the items in the ArrayList.

main method

Create two ArrayLists, one for Animal, and one for RedCat.

Use addCat to add “Tiger” to the animal ArrayList.

Use addCat to add “Tom”, “Siamese” and “Tiger” to the redCats ArrayList.

Use printAll to print the list in the animal ArrayList.

Use printAll to print the list in the redCat ArrayList.

Use deleteCat to delete the first item in the redCat ArrayList.

Use printAll to print the list in the redCat ArrayList.

Sample Output:

Cat Added named Tiger was added

Cat Added named Tom was added

Cat Added named Siamese was added

Cat Added named Tiger was added

The list of animals:

Tiger

The list of redCats:

Tom Siamese Tiger

Removed cat named Tom

The list of redCats after a deletion:

Siamese Tiger

Answer 1

Program Screenshots:

Animal.java

Cat.java

RedCat.java

WildCardTester.java

Program Code :

Animal.java

//Create a simple class called Animal instantiated with a name and a method toString which returns the name.
public class Animal {
   String name;

   public Animal(String name) {
       this.name = name;
   }

   @Override
   public String toString() {
       return name;
   }

}

Cat.java

//Create a simple class Cat which extends Animal, but adds no new instance variable or methods.
public class Cat extends Animal {

   public Cat(String name) {
       super(name);
      
   }

}

RedCat.java

//Create a simple class RedCat which extends Cat, but adds no new instance variable or methods.
public class RedCat extends Cat {

   public RedCat(String name) {
       super(name);
      
   }

}

WildCardTester.java

//Create a class with the main method and methods addCat, deleteCat and printAll as follows
import java.util.ArrayList;
import java.util.List;

public class WildCardTester {

   public static void main(String[] args) {
      
//       Create two ArrayLists, one for Animal, and one for RedCat.
       List<Animal> animal = new ArrayList<Animal>();
       List<RedCat> redCat = new ArrayList<RedCat>();
       addCat(animal,"Tiger");
       addCat(redCat,"Tom");
       addCat(redCat,"Siamese");
       addCat(redCat,"Tiger");
       System.out.println("The list of animals:");
       for(Animal a : animal) {
           System.out.print(a + " ");
       }
       System.out.println();
       System.out.println("The list of redCats:");
       for(RedCat r : redCat) {
           System.out.print(r + " ");
       }
       System.out.println();
       deleteCat(redCat, "Tom");
       printAll(redCat);
   }
//   printAll method:Has a single parameter of an ArrayList with a wildcard type. Prints out all the items in the ArrayList.
   private static void printAll(List<? super RedCat> lists) {
       System.out.println("The list of redCats after a deletion:");
       for(Object r : lists) {
           System.out.print(r + " ");
       }
      
   }
  
   /*deleteCat method:Has two parameters, an ArrayList with an upper bound of Cat,
   and a String with the name of a Cat to be deleted.
   Deletes the identified Cat reference to the ArrayList, and prints out a line as shown in the sample output below.*/

   private static void deleteCat(List<RedCat> lists1, String name1) {
       System.out.println("Removed cat named " + name1);
       for(RedCat rc : lists1) {
           if(rc.name.equals(name1)) {
               lists1.remove(rc);
               break;
           }
       }
      
   }
  
   /*addCat method :Has two parameters, an ArrayList with a lower bound of RedCat, and a String with the name of a Cat.
   Adds the identified Cat reference to the ArrayList, and prints out a line as shown in the sample output below.*/
   private static void addCat(List<? super RedCat> lists, String name1) {
       lists.add(new RedCat(name1));
       System.out.println("Cat Added named " + name1 + " was added");
      
      
   }

}

Sample Output: