New Java programmers can find it difficult to understand the difference between the PriorityQueue and TreeSet collections. This is because they both have a lot of functional similarities. For instance, they both offer O (log (N)) time complexity for adding and searching elements; both are non-synchronized and present elements in sorted order. The two, however, differ greatly from each other. This post will discuss various differences between the Java TreeSet and the PriorityQueue.
The Differences between PriorityQueue and TreeSet in Java
Here are various differences between the PriorityQueue and TreeSet in Java
First of all, TreeSet is a Set, and therefore, like all Sets, it does not allow duplicate elements, while priorityQueue is a Queue, and therefore, it allows duplicate elements as well. This implies that PriorityQueue can contain multiple elements with equal values.
Unlike the PriorityQueue, which allows you to retrieve both the smallest and largest elements in 0(1) time, the TreeSet does not allow you to retrieve either the largest or smallest elements in 0(1) time.
In priorityQueue, aside from the root, all elements can or may ignore the order, while TreeSets always present all elements in sorted order.
Examples
Example of a TreeSet
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import java.util.TreeSet; public class TreeSet_Example { public static void main(String[] args) { TreeSet<String> treeseta = new TreeSet<String>(); treeseta.add("Tomato"); treeseta.add("Carrots"); treeseta.add("Cabage"); System.out.println("Tree Set is " + treeseta); String check = "Tomato"; System.out.println("Contains " + check + " " + treeseta.contains(check)); System.out.println("First Value " + treeseta.first()); System.out.println("Last Value " + treeseta.last()); String val = "Tomato"; System.out.println("Higher " + treeseta.higher(val)); System.out.println("Lower " + treeseta.lower(val)); } } |
Output:
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Contains Tomato true First Value Cabbage Last Value Tomato Higher null Lower Carrots |
Example of PriorityQueue
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import java.util.PriorityQueue; public class PriorityQueue_Example { public static void main(String[] args) { PriorityQueue<String> prioritiseQueue = new PriorityQueue<>(); prioritiseQueue.add("Chicken"); prioritiseQueue.add("Beef"); prioritiseQueue.add("Fish"); System.out.println(prioritiseQueue.peek()); System.out.println(prioritiseQueue.poll()); System.out.println(prioritiseQueue.peek()); } } |
Output
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Beef Beef Chicken |
Keywords: Difference between PriorityQueue and TreeSet
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