MyQueue.java

package queue;

import java.util.LinkedList;
import java.util.Queue;
import java.util.Iterator;

public class MyQueue {
	
	public static void main(String[] args) {
		
		System.out.println("***       Fun with Queue       ***");
		System.out.println();
		
		//Use the generic <Queue> Interface type to perform operations instead
		//of exact implementation class <LinkedList>
		Queue<String> queue = new LinkedList<String>();
		
		//Insert five string elements using <add> operation
		queue.add("first element");
		queue.add("second element");
		queue.add("third element");
		queue.offer("fourth element");
		queue.offer("fifth element");
		
		System.out.println("Queue contents:");
		System.out.println(queue);
		System.out.println();
		
		//Check the size of queue
		int size = queue.size();
		
		System.out.println("Size of the queue = " + size);
		System.out.println();
		
		//Check if specified element is present in queue
		boolean containsSixthElement = queue.contains("sixth element");
		boolean containsThirdElement = queue.contains("third element");
		
		//This element is not present inside the queue
		System.out.print("Does the Queue contain \"sixth element\" --> ");
		if (containsSixthElement == true) {
			System.out.println("Yes");
		}
		else {
			System.out.println("No");
		}
		
		//This element is present inside the queue
		System.out.print("Does the Queue contain \"third element\" --> ");
		if (containsThirdElement == true) {
			System.out.println("Yes");
		}
		else {
			System.out.println("No");
		}
		
		System.out.println();
		
		//Iterate through the queue
		Iterator<String> iterator = queue.iterator();
		int elementCount = 0;
		
		System.out.println("Iterating through the Queue:");
		while(iterator.hasNext() == true) {
			String currentElement = iterator.next();
			System.out.println("Position = " + elementCount++ + 
					" Element = \"" + currentElement + "\"");
		}
		
		//Examine the queue using <peek> and <element> operation
		System.out.println();
		System.out.println("Examine head element using <peek> operation:");
		String headElement = queue.peek();
		System.out.println("<peek> operation : Head Element --> " + 
				headElement);		
		
		System.out.println("Examine head element using <element> operation:");
		headElement = queue.element();
		System.out.println("<element> operation : Head Element --> " + 
				headElement);
		
		//Remove the current head element using <poll> operation
		System.out.println();
		System.out.println("Removing Elements:");
		String firstElement = queue.poll();
		System.out.println("First Element to be extracted (poll) = \"" + 
				firstElement + "\"");
				
		//Remove the current head element using <remove> operation
		String secondElement = queue.remove();
		System.out.println("Second Element to be extracted (remove) = \"" + 
				secondElement + "\"");
		
		//Queue size should now reflect the lesser number of elements
		System.out.println();
		System.out.println("Checking Queue size after extraction of elements:");
		int currentSize = queue.size();
		
		System.out.println("Original Queue Size = " + size);
		System.out.println("Current Queue Size = " + currentSize);
		
		//Remove head element
		System.out.println();
		System.out.println("Removing head element:");
		String removedElement = queue.remove();
		System.out.println("Removed Element = " + removedElement);
		System.out.println("Checking Queue size after removal of element:");
		int reducedSize = queue.size();
		System.out.println("Reduced Queue Size = " + reducedSize);
		
		//Remove all elements from queue
		queue.clear();
		currentSize = queue.size();
		
		System.out.println();
		System.out.println("Queue Size after removing all elements = " + 
				currentSize);
	}
}