The PriorityQueue and TreeSet both are the classes defined inside the Collection Framework. In this article, we will learn the differences between PriorityQueue and TreeSet. PriorityQueue is an implementation of Queue interface and the TreeSet is the implementation of the Set interface. There are some differences exists between them. So we have tried to list out the differences between PriorityQueue and TreeSet.
1. PriorityQueue: A PriorityQueue is used when the objects are supposed to be processed based on the priority. It is known that a Queue follows the First-In-First-Out algorithm, but sometimes the elements of the queue are needed to be processed according to the priority, that’s when the PriorityQueue comes into play. The PriorityQueue is based on the priority heap. The elements of the priority queue are ordered according to the natural ordering, or by a Comparator provided at queue construction time, depending on which constructor is used.
PriorityQueue Demo:
Java
// Java program to demonstrate the// working of PriorityQueueimport java.util.*; class PriorityQueueDemo { // Main Method public static void main(String args[]) { // Creating empty priority queue PriorityQueue<String> pQueue = new PriorityQueue<>(); // Adding elements to the pQueue using add() pQueue.add("Geeks"); pQueue.add("For"); pQueue.add("Geeks"); // Printing the top element of PriorityQueue System.out.println(pQueue.peek()); // Printing the top element and removing it // from the PriorityQueue container System.out.println(pQueue.poll()); // Printing the top element again System.out.println(pQueue.peek()); }} |
For For Geeks
2. TreeSet: TreeSet is one of the most important implementations of the SortedSet interface in Java that uses a Tree for storage. The ordering of the elements is maintained by a set using their natural ordering whether or not an explicit comparator is provided. This must be consistent with equals if it is to correctly implement the Set interface. It can also be ordered by a Comparator provided at set creation time, depending on which constructor is used. The TreeSet implements a NavigableSet interface by inheriting AbstractSet class.
TreeSet Demo:
Java
// Java code to demonstrate// the working of TreeSet import java.util.*;class TreeSetDemo { public static void main(String[] args) { // Creating an empty TreeSet TreeSet<String> ts = new TreeSet<String>(); // Elements are added using add() method ts.add("Geek"); ts.add("For"); ts.add("Geeks"); System.out.println("Tree Set is " + ts); String check = "Geeks"; // Check if the above string exists in // the treeset or not System.out.println("Contains " + check + " " + ts.contains(check)); // Print the first element in // the TreeSet System.out.println("First Value " + ts.first()); // Print the last element in // the TreeSet System.out.println("Last Value " + ts.last()); String val = "Geek"; // Find the values just greater // and smaller than the above string System.out.println("Higher " + ts.higher(val)); System.out.println("Lower " + ts.lower(val)); }} |
Differences between PriorityQueue and TreeSet
|
PriorityQueue |
TreeSet |
|---|---|
| PriorityQueue uses the Queue underlying data structure | TreeSet uses the Set underlying data structure. |
| PriorityQueue allows the duplicate elements | TreeSet doesn’t allow the duplicate elements |
| In PriorityQueue, apart from the root rest of the elements may or may not follow any order. | In TreeSet all the elements remain in the sorted order. |
| Using PriorityQueue, we can retrieve largest or smallest element in O(1) time. | TreeSet doesn’t provide a way to retrieve largest or smallest element in O(1) time, but since they are in sorted order it gets the first or last element in O(1) time. |
| PriorityQueue comes in JDK 1.5. | TreeSet comes in JDK 1.4. |
