Menu driver program written in Java for performing queue operations

Queue is a linear data structure, which in Java is regarded as a collection that works according to the FIFO (first in, first out) principle.

In this article, we will see how to perform different queue operations such as enqueue, dequeue, queue front, queue size, and whether the queue is empty or not using Java programming language. We will use switch case to implement this application.

Show you some examples

Example 1

Suppose we have entered a queue of size 6 with elements [2, 6, 5, 8, 7, 3]. Then we will perform the Enqueue operation and add element 0. So the updated list is -
[2, 6, 5, 8, 7, 3, 0]

Example-2

In the same queue we perform Dequeue operation and remove element 2. Then the
updated list is - [6, 5, 8, 7, 3, 0]

Example 3

Now we find the front of the queue. The front element is 6.

The Chinese translation of

Instance-4

is:

Instance-4

Suppose we have created an array containing 6 elements and array elements are [2,4,6,2,6,8]. Now we will print the smallest element in an array. And hence result will be.
Smallest element present in given array: 2

The Chinese translation of

Instance-5

is:

Instance-5

Now we find if the queue is empty or not. And the result is “The queue is not empty”.

grammar

To queue elements, we use the add() method

The following is the syntax of "add()"

list.add(s);

In order to dequeue the elements in the queue, we use the remove() method

The following is the syntax of "remove()"

list.remove(s);

To view the previous element in the queue, we use the peek() method

The following is the syntax of "peek()"

list.peek();

To check whether the queue is empty, we use the isEmpty() method

The following is the syntax of "isEmpty()":

list.isEmpty();

algorithm

Step-1 - Ask the user to enter the desired queue.

Step-2 − Display the menu.

Step 3 - Ask the user to enter their selections.

Step-4 - Use the switch box to go to the selection and perform the action.

Step 5 - Print the results.

Let us see the program to understand it clearly.

Example

import java.util.*;
public class Main{
   public static void main(String args[]){
      LinkedList<String> list = new LinkedList<>();
      //declare your list
      Scanner sc = new Scanner(System.in);
      //create a scanner class object
      System.out.print("Enter the queue size : ");
      int nbr = sc.nextInt();
      //read the number of element
      System.out.println("Enter the element : ");
      sc.nextLine();
      do {
         list.add(sc.nextLine());
         nbr--;//decrement the index
      } 
      while (nbr > 0);
      //repeat until the index will be 0
      System.out.println("The queue contains: ");
      System.out.println(list);//print your list
      mainLoop: while (true) {
         Scanner sc1 = new Scanner(System.in);
         System.out.println("\n***Menu***");
         System.out.println("1. Perform Enqueue operation");
         System.out.println("2. Perform Dequeue operation");
         System.out.println("3. Prints the front of the queue");
         System.out.println("4. Print the size of the queue");
         System.out.println("5. Check if the queue is empty");
         System.out.println("6. Terminate the program");
         System.out.println("Enter action number (1-6): ");
         int command = sc.nextInt();
         switch(command){
            case 1:
               System.out.print("Enter the element you want to enter in the queue : ");
               int num = sc.nextInt();
               String s = Integer.toString(num);
               list.add(s);
               System.out.println("updated list is: ");
               System.out.println(list);
               break;
            case 2:
               list.remove();
               System.out.println("updated list is: ");
               System.out.println(list);
               break;
            case 3:
               System.out.println("The front element is " + list.peek());
               break;
            case 4:
               System.out.println("The queue size is " + list.size());
               break;
            case 5:
            if (list.isEmpty()) {
               System.out.println("The queue is empty");
            }
            else {
               System.out.println("The queue is not empty");
            }
            break;
            case 6:
               System.out.println("Program terminated");
               break mainLoop;
            default:
               System.out.println("Wrong choice!!");
            
         }
      }
   }
}

Output

Enter the queue size : 4
Enter the element :
1
2
3
4
The queue contains:
[1 , 2, 3, 4]

***Menu***
1. Perform Enqueue operation
2. Perform Dequeue operation
3. Prints the front of the queue
4. Print the size of the queue
5. Check if the queue is empty
6. Terminate the program
Enter action number (1-6):
1
Enter the element you want to enter in the queue : 5
updated list is:
[1 , 2, 3, 4, 5]

***Menu***
1. Perform Enqueue operation
2. Perform Dequeue operation
3. Prints the front of the queue
4. Print the size of the queue
5. Check if the queue is empty
6. Terminate the program
Enter action number (1-6):
2
updated list is:
[2, 3, 4, 5]

***Menu***
1. Perform Enqueue operation
2. Perform Dequeue operation
3. Prints the front of the queue
4. Print the size of the queue
5. Check if the queue is empty
6. Terminate the program
Enter action number (1-6):
3
The front element is 2

***Menu***
1. Perform Enqueue operation
2. Perform Dequeue operation
3. Prints the front of the queue
4. Print the size of the queue
5. Check if the queue is empty
6. Terminate the program
Enter action number (1-6):
4
The queue size is 4

***Menu***
1. Perform Enqueue operation
2. Perform Dequeue operation
3. Prints the front of the queue
4. Print the size of the queue
5. Check if the queue is empty
6. Terminate the program
Enter action number (1-6):
5
The queue is not empty

***Menu***
1. Perform Enqueue operation
2. Perform Dequeue operation
3. Prints the front of the queue
4. Print the size of the queue
5. Check if the queue is empty
6. Terminate the program
Enter action number (1-6):
6
Program terminated

In this article, we explored how to perform different queue operations in Java by using a menu-driven approach.

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