java queue example

implementations

// Array implementation of Queue
Queue<String> animal2 = new ArrayDeque<>();

// LinkedList implementation of Queue
Queue<String> animal1 = new LinkedList<>();

// Priority Queue implementation of Queue
Queue<String> animal 3 = new PriorityQueue<>();

java queue example

/**
 * @author lautturi.com 
 * Java example: java queue 
 */

import java.util.*;

public class Lautturi {

	public static void main(String args[]) {

		// use non-primative types when constructing
		Queue<Integer> queue = new LinkedList<Integer>();

		//  adds a value to the back of queue:
		queue.add(1);
		queue.add(3);
		queue.add(5);
		queue.add(2);
		queue.add(4);
		queue.add(6);
		
		//print the contents of the Queue
		System.out.println("Queue:"+queue);
		
		// removes first element from the queue
		int first = queue.remove();
		
		System.out.println("first:"+first);
		System.out.println("Queue:"+queue);

		//  just returns front value without removing:
		int peek = queue.peek();
		
		System.out.println("peek:"+peek);
		System.out.println("Queue:"+queue);
		
		// returns head of the queue
		int element = queue.element();
		
		System.out.println("element:"+element);
		System.out.println("Queue:"+queue);
		
		// removes and returns the head
		int poll = queue.poll(); 

		System.out.println("poll:"+poll);
		System.out.println("Queue:"+queue);
		
	}
}

output:

Queue:[1, 3, 5, 2, 4, 6]
first:1
Queue:[3, 5, 2, 4, 6]
peek:3
Queue:[3, 5, 2, 4, 6]
element:3
Queue:[3, 5, 2, 4, 6]
poll:3
Queue:[5, 2, 4, 6]