• Java Data Structures Tutorial

Java Data Structures - Creating a Queue



Java provides an interface known as Queue which represents the queue data structure. This interface have various subclasses such as ArrayBlockingQueue, ArrayDeque, ConcurrentLinkedDeque, ConcurrentLinkedQueue, DelayQueue, LinkedBlockingDeque, LinkedBlockingQueue, LinkedList, LinkedTransferQueue, PriorityBlockingQueue, PriorityQueue, SynchronousQueue.

You can create a queue in Java by instantiating any of these classes. Here in our examples we will try to create a queue by instantiating the PriorityQueue class.

  • It is an unbounded priority queue based on a priority heap.

  • The elements of it are ordered according to their natural ordering, or by a Comparator provided at queue construction time, depending on which constructor is used.

  • It does not permit null elements.

  • It relies on natural ordering also does not permit insertion of non-comparable objects.

Example

import java.util.PriorityQueue;
import java.util.Queue;

public class CreatingQueue {
   public static void main(String args[]) {
      //Create priority queue
      Queue <String>  prQueue = new PriorityQueue <String> () ;      
      
      //Adding elements
      prQueue.add("JavaFX");
      prQueue.add("Java");
      prQueue.add("HBase");
      prQueue.add("Flume");
      prQueue.add("Neo4J");
      
      System.out.println("Priority queue values are: " + prQueue) ; 
   }
}

Output

 
Priority queue values are: [Flume, HBase, Java, JavaFX, Neo4J]
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