One other key distinction between TreeSet and PriorityQueue is iteration order, although you may entry parts from the top in sorted order like head at all times offer you lowest or highest precedence factor relying upon your Comparable or Comparator implementation iterator returned by PriorityQueue does not present any ordering assure.
Solely assure PriorityQueue provides that head will at all times be the smallest or largest factor. Then again, TreeSet retains all parts in sorted order, and the iterator returned by TreeSet will assist you to entry all parts in that sorted order.
This is among the ceaselessly requested Assortment interview questions and what makes it fascinating is the refined distinction between quite a lot of similarities between PriorityQueue and TreeSet. You need to use one rather than one other in some eventualities however not in all eventualities and that is what the interviewer is in search of when he requested this query to you on Interview.
What are similarities between PriorityQueue and TreeSet
Earlier than trying on the distinction between Precedence Queue and TreeSet, let’s first perceive the similarities between them. This may provide help to to think about eventualities the place you should utilize a PriorityQueue rather than TreeSet or vice-versa.
1. ThreadSafety
The primary similarity between PriorityQueue and TreeSet is that each will not be thread-safe, which suggests you can’t share them between a number of threads. If a number of threads are required to switch the TreeSet on the identical time, then it’s essential to synchronize their entry externally.
2. Ordering
The third similarity between PriorityQueue and TreeSet is that each can be utilized to entry parts in a selected order. TreeSet is a SortedSet, therefore it at all times retains the weather within the order outlined by their Comparator or pure order if there isn’t any Comparator outlined, whereas PriorityQueue will at all times make it possible for head incorporates the bottom or highest worth relying upon the order imposed by Comparator or Comparable.
3. Eligibility
Once I say eligibility, which suggests which objects may be saved in PrioritySet and TreeSet? Is there any restriction or all objects are allowed? Nicely, there may be, you may solely retailer objects which implement Comparable or Comparator in each PriorityQueue and TreeSet as a result of the gathering lessons are chargeable for preserving their dedication i.e. PriorityQueue should alter after each insertion or deletion to maintain the bottom or highest factor in head place. Equally, TreeSet should re-arrange parts in order that they continue to be the sorted order specified by Comparator or pure order imposed by Comparable.
4. Efficiency
That is one level the place you will notice each similarities and variations between PriorityQueue and TreeSet in Java, like each, present O(log(N)) complexity for including, eradicating, and looking parts, however if you wish to take away the very best or lowest precedence factor then PriorityQueue provides O(1) efficiency as a result of it at all times retains the factor within the head, very similar to a heap knowledge construction i.e. minimal heap the place the foundation is at all times the minimal worth.
Distinction between PriorityQueue and TreeSet
Now, that you already know and perceive the similarities between TreeSet and PrioritySet, let’s have a look at how totally different they’re? and why you can’t use PrioritySet rather than TreeSet in Java?
1. Underlying Information Construction
This at first distinction is the underlying knowledge construction. PriorityQueue is a Queue and that is why it gives the performance of the FIFO knowledge construction, whereas TreeSet is a Set and does not present the Queue API.
2. Duplicate Parts
The second distinction between them may be derived from the primary distinction i.e. properties of their underlying knowledge construction. Since TreeSet is a Set it does not enable duplicate parts however PriorityQueue could comprise duplicates. Within the case of ties, the top of the precedence queue is chosen arbitrarily.
3. Efficiency
The third distinction between TreeSet and PrirityQueue comes from their relative efficiency. The PriorityQueue gives the most important or smallest factor in O(1) time, which isn’t attainable by TreeSet. Since TreeSet is backed by a red-black tree, the search operation will take O(logN) time.
Because of this in case you are growing an software the place precedence issues e.g. a job scheduling algorithm the place you at all times wish to execute the job with the very best precedence, it is best to use a PriorityQueue knowledge construction.
4. Availability
The fifth and final distinction between PriorityQueue and TreeSet class are that the previous was added in JDK 1.5 whereas TreeSet was obtainable from JDK 1.4 itself. This isn’t a really vital distinction within the age of Java 8, however in case you are working with legacy methods nonetheless operating on Java 1.5, some extent value remembering.
5. Ordering
The fourth distinction, which is extra refined than you suppose as a result of in similarities I’ve informed that each are chargeable for preserving some order. The important thing level is that in TreeSet all parts stay within the sorted order, whereas in precedence queue aside from the foundation, which is assured to be smallest or largest relying upon Evaluating logic, remainder of the factor could or could not observe any order.
This implies should you retailer the identical parts within the TreeSet and PriorityQueue and iterate over them, then their order shall be totally different. TreeSet will print them in sorted order however PriorityQueue is not going to till you’re at all times getting the factor from the top. You can too learn a great core Java guide like Java: The Full Reference, Ninth Version to study extra about PriorityQueue implementation in Java.
Utilizing PriorityQueue and TreeSet in Java Program
Now, let’s some code to spotlight the distinction between PriorityQueue and TreeSet in Java. For those who bear in mind essentially the most refined distinction I point out within the earlier paragraph was that TreeSet retains all parts within the sorted order, whereas PriorityQueue solely retains the foundation or head into order.
I imply the bottom factor will at all times be at root in PriorityQueue. For those who use ballot() which consumes the top and removes it, you’ll at all times retrieve the weather in rising order from PriorityQueue, as proven within the following Java program.
import java.util.Collections; import java.util.Date; import java.util.Iterator; import java.util.Record; import java.util.PriorityQueue; import java.util.Queue; import java.util.Set; import java.util.TreeSet; /** * Java Program to reveal distinction between PriorityQueue * and TreeSet. * * @writer WINDOWS 8 * */ public class App { public static void important(String args[]) { SetsetOfNumbers = new TreeSet<>(); Queue queueOfNumbers = new PriorityQueue<>(); // inserting parts into TreeSet and PriorityQueue setOfNumbers.add(202); setOfNumbers.add(102); setOfNumbers.add(503); setOfNumbers.add(33); queueOfNumbers.add(202); queueOfNumbers.add(102); queueOfNumbers.add(503); queueOfNumbers.add(33); // Iterating over TreeSet System.out.println("Iterating over TreeSet in Java"); Iterator itr = setOfNumbers.iterator(); whereas(itr.hasNext()){ System.out.println(itr.subsequent()); } // Iterating over PriorityQueue System.out.println("Iterating over PriorityQueue in Java"); itr = queueOfNumbers.iterator(); whereas(itr.hasNext()){ System.out.println(itr.subsequent()); } // Consuming numbers utilizing from head in PriorityQueue System.out.println("polling a PriorityQueue in Java"); whereas(!queueOfNumbers.isEmpty()){ System.out.println(queueOfNumbers.ballot()); } } } Output: Iterating over TreeSet in Java 33 102 202 503 Iterating over PriorityQueue in Java 33 102 503 202 polling a PriorityQueue in Java 33 102 202 503
This proves the purpose that TreeSet retains all parts in sorted order whereas PriorityQueue solely cares concerning the root or head place. This sort of element is essential from the Java certification perspective as properly, you’ll discover quite a lot of questions primarily based upon such refined particulars in mock exams in addition to on the true examination.
Abstract
Lastly, right here is the abstract of all of the variations between TreeSet and PriorityQueue in Java on the good tabular format for straightforward reference:
That is all concerning the distinction between TreeSet and PrirorityQueue in Java. Although each present some type of sorting functionality there’s a enormous distinction between the habits of those two assortment lessons.
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