Question

In Java, create a program implementing the functionalities of a standard queue in a class called Queue3503. You will test the functionalities of the Queue3503 class from the main() method of the Main class. In a queue, first inserted items are removed first and the last items are removed at the end (imagine a line to buy tickets at a ticket counter).

Do NOT change your class name from "Main". The Main class should come first in your code. Your filename should be "Main.java".

The Queue3503 class will contain:
a. An int[] data filed named elements to store the int values in the queue.
b. An int data field named size that stores the number of elements in the queue.
c. A no-arg constructor that creates a Queue object with default capacity 0.
d. A constructor that takes an int argument representing the capacity of the queue.
e. A method with signature enqueue(int v) that adds the int element v into the queue.
f. A method with signature dequeue() that removes and returns the first element of the
queue.
g. A method with signature empty() that returns true if the queue is empty.
h. A method with signature getSize() that returns the size of the queue (return type is hence
int)).

The queue class you develop should be tested using the following steps: (In other words, your program named Main will consist of the following)

a. Start your queue with an initial capacity of 8.
b. When the dequeue() method is called, an element from the queue at the beginning of the queue must be removed.

c. The main() method in your Main class should consist of statements to:
i. Create a queue object;
ii. Call enqueue() to insert twenty integers (taken from the user) into the queue.
iii. After the above task is completed, include a for-loop that will print out the contents of the queue.

d. After printing the queue filled with twenty integers, call dequeue() repeatedly to remove the beginning element of the queue.

e. Print the contents of the queue after removing every fifth number.

f. For your reference, the execution of the Main program is shown below. User inputs for populating the Queue is shown in the first line. Next, your program outputs are shown.

Your program MUST follow the sample output format shown below.

Sample Run

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

Initial content: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

After removing 5 elements: 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

After removing 5 elements: 11 12 13 14 15 16 17 18 19 20

After removing 5 elements: 16 17 18 19 20

Answer 1

Here is the implementation of Queue in Main.java :

import java.util.Scanner;

public class Main {

   public static void main(String[] args) {
       Scanner src = new Scanner(System.in);
       Queue3503 queueObj = new Queue3503(8);
       System.out.println("Please enter 20 elements");
       for (int i = 0; i < 20; i++) {
           queueObj.enqueue(src.nextInt());
       }

       System.out.print("Initial content: ");
       for (int i = 0; i < queueObj.getSize(); i++) {
           System.out.print(queueObj.displayElement(i) + " ");
       }
       System.out.println();
      
       int counter=queueObj.getSize();
       int counter2=0;
      for(int i=0;i<counter;i++) {
          queueObj.dequeue();
          counter2++;
          if(counter2%5==0 && !queueObj.empty()) {
              System.out.print("After removing 5 elements: ");
              for(int j=0;j<queueObj.getSize();j++) {
                  System.out.print(queueObj.displayElement(j) + " ");
                  }
                  System.out.println();
              }
          }
   }
}

class Queue3503 {

   private int size;
   int[] elements;

   public Queue3503() {
       size = 0;
       elements = new int[size];
   }

   public Queue3503(int n) {
       elements = new int[n];
   }

   void enqueue(int v) {
       if (size < elements.length) {
           elements[size++] = v;
       } else {
           int tempEle[] = new int[elements.length + 5];
           for (int i = 0; i < size; i++) {
               tempEle[i] = elements[i];
           }
           elements = tempEle;
           elements[size++] = v;
       }
   }

   public int dequeue() {
       if (empty()) {
           return -1;
       } else {
           int firstElement = elements[0];
           for (int i = 0; i < size - 1; i++) {
               elements[i] = elements[i + 1];
           }
           size--;
           return firstElement;
       }
   }

   public boolean empty() {
       return size == 0;
   }

   public int getSize() {
       return size;
   }

   public int displayElement(int n) {
       if (n < size)
           return elements[n];
       return -1;
   }
}

This is the output i have received after running the program:

Please enter 20 elements
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
Initial content: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
After removing 5 elements: 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
After removing 5 elements: 11 12 13 14 15 16 17 18 19 20
After removing 5 elements: 16 17 18 19 20