Question

You need to write a class called SingleItemBox (in a file called SingleItemBox.java that you create). This class has a constructor that takes a single item (of any type) and puts it in the box. You also need a method called getItem() which provides the item back to the user but does not remove it from the box (this is an “accessor”, if you remember, sometimes called a “getter”).

public class BoxUsageDemo {
   /**
   * This is a main method with demo code.
   * @param args command line args (not used)
   */
   public static void main(String[] args) {
       //demo putting an apple in a box
       class Apple { }
      
       //make an apple
       Apple a1 = new Apple();
      
       //put the apple in a box
       SingleItemBox<Apple> appleBox = new SingleItemBox<>(a1);
      
       //check that the apple was put in the box
       if(appleBox.getItem().equals(a1)) {
           System.out.println("yay 1");
       }
      
      
      
       //demo putting a banana in a box
       class Banana { }
      
       //make a banana
       Banana b1 = new Banana();
      
       //put the banana in a box
       SingleItemBox<Banana> bananaBox = new SingleItemBox<>(b1);
      
       //check that the banana was put in the box
       if(bananaBox.getItem().equals(b1)) {
           System.out.println("yay 2");
       }
      
      
      
       //demo putting a banana in a box
       class Cat { }
      
       //make a banana
       Cat c1 = new Cat();
      
       //put the banana in a box
       SingleItemBox<Cat> catPlayBox = new SingleItemBox<>(c1);
      
       //check that the banana was put in the box
       if(catPlayBox.getItem().equals(c1)) {
           System.out.println("yay 3");
       }
   }
}

Answer 1

SOURCE CODE IN JAVA:

SingleItemBox.java

//generic class to accept and store an object of any class

class SingleItemBox<T>

{

//instance variable

private T obj;

//parametrized constuctor

public SingleItemBox(T obj)

{

this.obj=obj;

}

//getter method

public T getItem()

{

return obj;

}

}

BoxUsageDemo.java

class Main

{

public static void main(String[] args) {

//demo putting an apple in a box

class Apple { }

//make an apple

Apple a1 = new Apple();

//put the apple in a box

SingleItemBox<Apple> appleBox = new SingleItemBox<>(a1);

//check that the apple was put in the box

if(appleBox.getItem().equals(a1)) {

System.out.println("yay 1");

}

//demo putting a banana in a box

class Banana { }

//make a banana

Banana b1 = new Banana();

//put the banana in a box

SingleItemBox<Banana> bananaBox = new SingleItemBox<>(b1);

//check that the banana was put in the box

if(bananaBox.getItem().equals(b1)) {

System.out.println("yay 2");

}

//demo putting a banana in a box

class Cat { }

//make a banana

Cat c1 = new Cat();

//put the banana in a box

SingleItemBox<Cat> catPlayBox = new SingleItemBox<>(c1);

//check that the banana was put in the box

if(catPlayBox.getItem().equals(c1)) {

System.out.println("yay 3");

}

}

}

OUTPUT: