Here’s a hierarchical diagram explaining things in a much better way: It extends AbstractQueue class which in turn implements Queue to rake in its benefits. Priority Queue Java or PriorityQueue Class is one of those classes that implement Queue interface. One of the crucial classes that inherit Queue Interface’s methods is PriorityQueue which is our next topic. There are two classes that implement Queue interface and they are: Since we cannot instantiate an interface, we will use one of its inheriting classes to see all the aforementioned methods in an example. NOTE: A queue doesn’t allow the insertion of null elements. Out of these four, the last two namely: poll() and remove() also remove the head from the queue. The last four methods namely, element(), peek(), poll() and remove() more or less do the same thing – retrieves the head of the queue. There are only six methods in here and they are: Queue InterfaceĪs you might have already guessed Queue in Java is an Interface that extends Collection Interface. So the first element is removed first and the last element gets removed last. It follows FIFO meaning it orders elements on the basis of first in first out. So with that, we have established that a queue follows a FIFO.Ī Queue in Java is no different.

Such a kind of setup of “first in first out” is also popularly abbreviated as FIFO. If you might remember the first person to enter the queue is the first to get out too once his/her job is done. Generally speaking, what do you really mean by queue? A line, right? You would know, now wouldn’t you? How many times in your life have you been forced to stand in a barely moving queue. So what was it like? Not the experience.

Make sure you have completely understood List before proceeding to learn about Java Queue FIFO.Īs per the hierarchy that we have seen for JCF, queue interface stands as our next topic. Queue in Java chapter is an immediate successor of Java Collections Framework that we had seen earlier.

Priority queue java example