Step by Step solution about How to resolve the algorithm Queue/Usage step by step in the Java programming language

Java Queues Using the LinkedList Class

The provided Java code demonstrates the use of queues implemented using the LinkedList class in the java.util package.

Queue Interface and Implementation

• Queue: A queue is a data structure that follows the first-in, first-out (FIFO) principle. Items are added to the back (tail) of the queue and removed from the front (head).
• LinkedList: A linked list is a linear data structure that stores data in nodes, where each node contains a value and a reference to the next node. It can be used as a queue by adding and removing elements at the head and tail.

Java Implementation using LinkedList

1. Using the Queue Interface:

• Queue<Integer> queue = new LinkedList<Integer>();: Creates a queue that stores integer values.
• queue.isEmpty(): Checks if the queue is empty.
• queue.add(1): Adds the integer 1 to the tail of the queue.
• queue.remove(): Removes and returns the integer at the head of the queue.

Output:

true
[1, 2, 3]
1
[2, 3]
false

2. Using the LinkedList Class Directly:

• LinkedList queue = new LinkedList();: Creates a queue that can store any object.
• queue.add(new Integer(1)): Adds an Integer object containing the value 1 to the tail.
• queue.removeFirst(): Removes and returns the first element in the queue.

Output:

true
[1, 2, 3]
1
[2, 3]
false

Note:

• In the first example, the queue is declared and initialized as a Queue<Integer>, which means it can only store integers. This is done using generics to ensure type safety.
• In the second example, the queue is declared as a LinkedList<E> without a specified type parameter, so it can store objects of any type. However, the elements must be objects (e.g., Integer objects).
• Both implementations demonstrate the basic operations of a queue: adding elements to the tail, removing elements from the head, and checking for emptiness.

import java.util.LinkedList;
import java.util.Queue;
...
Queue<Integer> queue = new LinkedList<Integer>();
System.out.println(queue.isEmpty());      // empty test - true
// queue.remove();       // would throw NoSuchElementException
queue.add(1);
queue.add(2);
queue.add(3);
System.out.println(queue);                // [1, 2, 3]
System.out.println(queue.remove());       // 1
System.out.println(queue);                // [2, 3]
System.out.println(queue.isEmpty());      // false


import java.util.LinkedList;
...
LinkedList queue = new LinkedList();
System.out.println(queue.isEmpty());      // empty test - true
queue.add(new Integer(1));
queue.add(new Integer(2));
queue.add(new Integer(3));
System.out.println(queue);                // [1, 2, 3]
System.out.println(queue.removeFirst());  // 1
System.out.println(queue);                // [2, 3]
System.out.println(queue.isEmpty());      // false