document.getElementById("comment").setAttribute("id","a244a445d070c091f98aed394bab29f2");document.getElementById("e7c91e9251").setAttribute("id","comment"); Save my name, email, and website in this browser for the next time I comment. Below program illustrate the Java.util.HashSet.size() method: You will be notified via email once the article is available for improvement. The containsAll() method of Java HashSet is used to check whether two sets contain the same elements or not. This constructor constructs a default HashSet. OTgzYWZhZWY2ZTA2ZjYxMzY0OGEwOWQ2OWY1YWEyMzYyYTA4ZDc5MjU0MTIz Suppose we increase the load factor number above that. It is responsible for returning a shallow copy of this HashSet instance, with no cloning of the items themselves. A null element is permitted by this HashSet class providing time performance for operations like remove, add, etc. Architecture - 11. HashSet also implements Serializable and Cloneable interfaces. As a result, each hash set element has its hashcode. This constructor initializes the hash set by using the elements of the collection c. This constructor initializes the capacity of the hash set to the given integer value capacity. Essentially, this constructor creates an empty HashSet object with the initialCapacity and loadFactor supplied when the object is created. For instance. how can It extends from the AbstractSet class and implements the Set Java interface. This means that the iteration order of Java HashSet elements doesnt remain constant. The Java.util.HashSet.size() method is used to get the size of the HashSet or the number of elements present in the HashSet. The Set interface inherits the Collection and Iterable interfaces in a hierarchical sequence. Book or a story about a group of people who had become immortal, and traced it back to a wagon train they had all been on. In this example, both the contents of the set and Count display to the console. HashSet requires one object to be added (Object o). For instance. Affordable solution to train a team and make them project ready. YzAxNzgzNTYwNzhlYjBkNTNlMjU1MmIwZTM0NTlkODYwNjAzZmEyYWJhMWFk Java - The HashSet Class HashSet does not maintain the insertion order. ZTU3MGE5NTNlMWNiODJjN2M1NGI3MjEwYTNiNGMyNTAxN2QyMTk1YmY5OWQ1 To count the number of elements in a HashSet, use the size () method. Java HashSet wont return duplicate elements as If there is a duplicate element in the HashSet then the old value would be overwritten. I have a problem with my practice exercise. It creates a collection that uses a hash table for storage. This doesnt create an empty HashSet. However, the TreeSet is slower than HashSet. To make a HashSet, we must first make an object of the HashSet class. This constructor initializes both the capacity and the fill ratio (also called load capacity) of the hash set from its arguments. NTM4YTAwYWEwNzU1MGI3YjZmNzQwOTFiMTUzZjRiMTMxOTM4NmM4YmE2MmM0 Are there ethnically non-Chinese members of the CCP right now? Return Value: The method returns True if this set contains all the elements of other set otherwise it returns False. But you can fix this issue fast. MTAxZmRiMjcyNDMzMjY1OGIwOTE2NzJhNDY5NTkzMjFlMDYxYmRmZjgwYzA4 This website or its third-party tools use cookies, which are necessary to its functioning and required to achieve the purposes illustrated in the cookie policy. Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. Array list is ordered collection and allowed duplicates where HashSet is not, In Array List Dont follow default Sorting mechanism but In case Of Hash Set its possible and Insertion is not preserved in Hash set It builds an empty HashSet with initial capacity of 16 and load factor of .75. Computer Science - 25 As you can see there all the duplicate values are not present in the output including the duplicate null value. If the map contains an course and the same course is collected again the lambda expression (count0, count1) -> count0 + count1 handles it by summing the values. RemoveAll()- Removes all elements from the set with removeAll(). by Deepak Verma | Dec 30, 2018 | Java | 2 comments. NTczMDM3MTJiNzkzOTU0ZDhjNjE5YWFmZjcwY2RjYmFjNDJkMTRkMjBiNzUy The null element is allowed in this class. You mean this: Song s1 = new Song(zzz, zaheer, 23, 343); A load factor of .60 means that when HashSet is 60% full, the capacity of HashSet is automatically increased. Apart from the methods inherited from its parent classes, HashSet defines following methods Example The following program illustrates several of the methods supported by HashSet Live Demo The null object is allowed in HashSet. The load factor measures how full the HashSet can get before its capacity is adjusted automatically. OGJkNGM2MjYwOTdlNjM3NjBjMDRmNzMzN2QzZTkzYzUwYmU2MDI1Mzc1YmZi Java program to remove one element from a hashset, remove all the elements that belong to a different collection, remove those elements that satisfy a certain condition from the hashset and remove all the elements from the hashset. I'm a beginner in Java and is starting to learn how to use hashsets. These cookies will be stored in your browser only with your consent. Whereas the HashSet implements the Set interface, the HashMap, on the other hand, implements the Map interface. I have checked your techndeck.com and i see youve got some duplicate content so probably it is the reason that you dont rank high in google. OWQxZGJmYmQ0MTQ2NzU3OTRmZDg5ZDMyMWNhNTBmYjE3NGRlMTY1ZDIzYmJl By default, TreeSet elements are sorted ascending. Privacy Policy . Notice, the elements iterate in an unordered collection. The hash code is then used as the index at which the data associated with the key is stored. The addAll() method can perform a union between two sets. How to Copy or Append HashSet to Another HashSet in Java? If we want to make an empty HashSet with the name hashSet, we can do so as follows: Its used to set the hash sets capacity to the specified integer value. HashSet does not save duplicate things; if you give it two equal objects, it will only store the first, which is list1. Asking for help, clarification, or responding to other answers. }. ODE2MmFkOWVmYmNlMzQ1NjJkYjZjNjRhNmFmMDQ5Zjk0ZTk5ZjlhZDBkMmJh The Java Collections frameworks HashSet class implements the hash table data structures functionality. HashSet in Java HashSet extends Abstract Set and implements the Set , Cloneable, and Serializable interfaces, where E denotes the type of elements this Set keeps track of. Its used to make a standard HashSet. can equal objects be added to hashset ? This hierarchy can be represented as follows: HashSet class belongs to java.util package. Its used to return an iterator across this Sets elements. ZTViZDlkNGQzMmM3ZDlkMTUyYTYyY2E2Yjk3ODAxMmRmY2M3NWUwMTNkMGY1 MTY2YTRhOWQxNWE0NmE2ODc0ZDdlYzQwY2E2MzY1Zjc2ZjA0NzUzNmZjMDhh N2VhZWZkNjhkM2Q0NzBmNTI3NTc0OWZlNTE2NjA0MjE1YjcxN2QzNDkxZTJl YmNlZjk4NzYxNTFhNDY4ZmY4ZjExOTVkYTEwMWZjNzg4YWVhMDIzNzZhYTUy HashSet elements cannot be duplicated. Required fields are marked *. *; class HashSet1 { public static void main (String args []) { //Creating HashSet and adding elements HashSet<String> set=new HashSet (); set.add ("One"); MDNiYWM2MjBhNDQxYWE4YTk2MzI4ZmVmYjdlOWZlZWJlNWY5Y2RjNDdlNDc3 An elements hashcode is a unique identifier that aids in locating the element in a hash table. NWM2Y2JkZjYwYjdhMjhhYzZhOGQ0ZDQ4OGQzYTgzNTY2NTU3NzZhZjdlMmY3 If Count exceeds the capacity while adding elements, the capacity is set to the first prime number that is greater than double the previous capacity. What is the difference between a list and a set? We'll assume you're ok with this, but you can opt-out if you wish. Lets see a simple HashSet example, where we are adding few string elements to HashSet and then iterating the HashSet to print the elements. Take a look at the HashSet classs add() method: We can see that the HashSet classs add() method calls the supporting HashMap objects put() method by passing the element you specified as a key and the constant PRESENT as its value. If you like this post, please check out my other similar posts: Your email address will not be published. HashSet in Java With Examples The java HashSet class consists of several constructors. Then it would help if you synchronized it from the outside. public HashSet (int initialCapacity) Constructs a new, empty set; the backing HashMap instance has the specified initial capacity and default load factor (0.75). A load factor of 0.75 delivers very effective time and space complexity performance. Following is the list of constructors provided by the HashSet class. HashSet<T>.Count Property (System.Collections.Generic) As well see later in the article, the hash function properly distributes the elements among the buckets. How to call a method from another class Java Catch Multiple Exceptions explained with examples, Guide to Importing the Math Class in Java, StringBuilder in Java explained with examples. The following are the key features of the Java HashSet class: A list can have duplicate elements, whereas a Set only has unique ones. hs.add(s6); while (itr.hasNext()) { HashSet implements the Set interface and inherits the AbstratSet class in Java that uses a HashTable for storage. For search, insert, and delete, TreeSet takes O(Log n), which is more than HashSet. [null, Apple, Grapes, Fig, Mango, Orange] It implements the Set interface. Agree The HashSet class contains several methods used to manipulate the Set. A smart way to solve you problem would be to use Java Streams: This creates a Map with the course as key and the sum as value. Creating a HashSet In order to create a hash set, we must import the java.util.HashSet package first. By closing this banner, scrolling this page, clicking a link or continuing to browse otherwise, you agree to our Privacy Policy, Explore 1000+ varieties of Mock tests View more, By continuing above step, you agree to our, Financial Analyst Masters Training Program, Software Development Course - All in One Bundle. Why did Indiana Jones contradict himself? ZmNjZDVkNzg5NmYxYzhhZjQ0ZGU5NzA2NDI2MzBmODQ1M2JmZThkYWU4MGZm and It think by if HashSet has been modified after creation of iterator Below programs illustrate the HashSet.containsAll () method: Program 1: import java.util. This article is being improved by another user right now. Stack containsAll() method in Java with Example, LinkedHashSet containsAll() method in Java with Example, AbstractSet containsAll() method in Java with Example, CopyOnWriteArraySet containsAll() method in Java with Example, TreeSet containsAll() method in Java with Example. The default load factor remains .75. MTkwYjE3MDE5YmNiMzllMjZlN2ZjMGJlYjU1ODdmMDEwMjdjYmM0NjVjNjIx Copyright Tutorials Point (India) Private Limited. acknowledge that you have read and understood our. The following program illustrates several of the methods supported by HashSet , Enjoy unlimited access on 5500+ Hand Picked Quality Video Courses. Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide, The future of collective knowledge sharing. Not the answer you're looking for? MjY5MWNhZTFjNmRkZmI1MTRmNGFhY2E4NmI0YmVjNzQwYTVlZjJiMWIwODI3 Java HashSet class implements the Set interface, backed by a hash table which is actually a HashMap instance. Return Value: The method returns the size or the number of elements present in the HashSet. Retrieving the value of this property is an O(1) operation. He is crazy about technologies, fitness and traveling etc. The HashSet class is a part of the Java Collection API since JDK 1.2. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. 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To subscribe to this RSS feed, copy and paste this URL into your RSS reader. However, dummy values are not supported by HashMap. set = new HashSet<String> (); Generated by Wordfence at Sun, 9 Jul 2023 6:57:31 GMT.Your computer's time: document.write(new Date().toUTCString());. ZDRjZmRlOWM5ZjhkNGRhZWVmMmVjODhlYjYzYmQ5M2Y3Mzk2YTZkN2ZhYjEy Below programs illustrate the HashSet.containsAll() method: You will be notified via email once the article is available for improvement. HashSet compares two objects in a Set and detects duplicates using the equals() method. It derives from AbstractSet and implements the Set interface. A collection and demonstrating the use of Hashset(collection c) constructor. The underlying data structure is a hashtable in HashSet. He created & maintains Techndeck.com, Copyright 2018-2022 Techndeck.com | All Rights Reserved. But, HashMap uses hashing to keep and add things internally. The order in which objects are placed into HashSet is not guaranteed. The java HashSet class consists of several constructors. A Guide to HashSet in Java THE CERTIFICATION NAMES ARE THE TRADEMARKS OF THEIR RESPECTIVE OWNERS. You should share an working example oft your issue, so wie can reproduce it. I have 15 years of experience in the IT industry, working with renowned multinational corporations. Return Value: The method returns True if this set contains all the elements of other set otherwise it returns False. HashSet containsAll() method in Java with Example eyJtZXNzYWdlIjoiM2NlYTBmZmJlYTAwYzI3YTRkNzVlMzgxODNkODQ0MDM5 In case elements do not exist in this Set, it returns true. The value we put in HashSet functions as a key to the map Object, and Java utilizes a constant variable to store its value. Thanks! ZjBiYzFiNTFlYjliMGZkN2Q3YjQ2NzJhNzMxZjY3NGQ4ZWIzNmFmNjNmYzAz In a nutshell, this constructor is called whenever a conversion from a Collection object to a HashSet object is required. -----END REPORT-----. In this example, both the contents of the set and Count display to the console. This means that the iteration order of Java HashSet elements doesn't remain constant. Techndeck.coms author is Deepak Verma aka DV who is an Automation Architect by profession, lives in Ontario (Canada) with his beautiful wife (Isha) and adorable dog (Fifi). ZGNkYmVhYmYwNmQ2YTE4ZWE3MTM1YTI2YTI3YzJlMDNlNWYzMzM4ZGRlYWZm When are complicated trig functions used? In Java, TreeSet is backed by TreeMap. The capacity grows automatically as elements are added to the HashSet. There is a tool that generates content like human, just search in google: miftolos tools, Your email address will not be published. More info about Internet Explorer and Microsoft Edge. All Rights Reserved. For instance. ZWQxYzE1NDE3ZTVmZGE3Y2VhNWIzMzllYTlmYWNlMDJiOWFjZmEwNjQ1Mzlj We also use third-party cookies that help us analyze and understand how you use this website. This constructor is used to create an empty HashSet object with a capacity of 16 and a load factor of 0.75 by default. HashSet (Java Platform SE 8 ) A Self-Balancing Binary Search Tree is responsible for implementing TreeSet (Red-Black Tree). HashSet holds not only unique Objects but also unique Collections of Objects such as ArrayList, LinkedList, Vector, and so on. The following example demonstrates how to create, populate, and manipulate two HashSet objects. How does the theory of evolution make it less likely that the world is designed? HashSet is more time-consuming than HashMap. The iteration order of the Set is not guaranteed, which means that the class does not guarantee the same order of elements across time. This parameter refers to the set whose elements occurrence is needed to be checked in this set. What would stop a large spaceship from looking like a flying brick? Engineering - 20 System.out.println(itr.next()); Java assigns a dummy value for each value provided in the add(Object) method. NTFkZmE4MGU1ZjU2Yjc5ZmYyZWI5MjRmNjdiY2MxZTdiN2U2N2M2ZWRjNmNh HashSet in Java | HashSet Constructors, Methods and Examples Simplest Presentation of Java HashSet Click To Tweet. Lets see few examples of HashSet in Java. Some information relates to prerelease product that may be substantially modified before its released. What is the significance of Headband of Intellect et al setting the stat to 19? MjIifQ== Example of a Java HashSet that ignores duplicate items, Example of removing members from a Java HashSet, Example: a program for demonstrating how the HashSet Class works, Example: Program illustrating the Iteration Over HashSet, How to write web pages using HyperText Markup, How to make a clean code with JavaScript, JavaScript RegExp Object Regular Expressions. HashSet is one of the fundamental data structures in the Java Collections API. In TreeSet, these operations are likewise O(Log n), and HashSet does not implement them. MzEwNDYyOTMzYmZhNDJhZDM3NWI5NWI1MjkxY2NiYTM3NTM3YzhmZTBkNzdj It uses the Map interfaces delete method internally. They are: Below is the example to implement HashSet in Java: Create a hashset and add new elements to the created new set. What is the difference between HashSet & ArrayList. It is mandatory to procure user consent prior to running these cookies on your website. This constructor creates a HashSet object containing all the elements from the specified collection. He runs a Travel Youtube Channel as well. Returns the number of elements in this set (its cardinality). If we want to make a HashSet named hs, we can do it as follows: The Java HashSet class has the following methods: If the supplied element is not already present, it is added to the Set. This is usually performed by synchronizing on a natural encapsulation object for the Set. Note that the HashSet implementation is not synchronized in the sense that if multiple threads visit a hash set at the same time and at least one of the threads updates the Set, the Set must be synchronized externally. You might be asking why we require a key-value pair to enter a value in HashMap but only one value in Has. NzE0MjdhYTI2MGY3ZjBkYTY4M2M3ZmI5YmRjYzQ5ODZlMWFmYmVmYmIxM2Fj A hash table is used to implement HashSet. YzEwNDY1MmI1MWUwNmE2OGNlOGY5MThmNDI1NzMwM2JkMzJjZDAyYWYxNDdk IsEmpty() returns a boolean value. The declaration of HashSet in Java is: Initial capacity represents the initial data buckets allocated to HashSet, this automatically increases when HashSet gets full. With the help of examples, we have learned about various hash set methods and operations. Thank you for your valuable feedback! Hashset in Java with example - Best & Simplest Solution - Techndeck Still, this class doesnt guarantee on the order of the elements with time. Upgrade to Microsoft Edge to take advantage of the latest features, security updates, and technical support. From OP I can see that you need an association key-value container, so the most obvious way will be to use Map, check if the value present as a key, if not - add it with 1 counter, if present - add + 1: Doing in more tricky way, you can use mutable AtomicInteger as a counter: Thanks for contributing an answer to Stack Overflow! ZTU2Zjk5ZjNiZmFhOTEyMTA1NjU4ZDJhZTNiODhmN2YzMzZmNTFkMzFhYjdk Throws: IllegalArgumentException - if the initial capacity is less than zero. Here the fill ratio must be between 0.0 and 1.0, and it determines how full the hash set can be before it is resized upward. We should choose starting capacity intelligently to reduce the rehashing operation. document.getElementById( "ak_js_1" ).setAttribute( "value", ( new Date() ).getTime() ); Copyright 2012 2023 BeginnersBook . HashSet in Java explained with examples | Code Underscored Points to remember: HashSet elements would get returned in any random . We make use of First and third party cookies to improve our user experience. How can I remove a mystery pipe in basement wall and floor? It returns a boolean type. It creates the HashSet with the elements copied from the passed Collection. When the table has 12 elements and the internal capacity is 16, and the load factor is 0.75, the number of buckets will automatically increase. MDY5YWRiODQ1NDJjOWJlOTM4ZjA1OGM4ZmI0N2ZhZDE0Nzc1ZWM2Mzk0ZTg1 There are four ways to create a HashSet in Java: HashSet (): Constructs a new, empty set; the backing HashMap instance has default initial capacity of 16 and load factor of 0.75. NGYxOTY0YTcyZmQ5MTFiZWZlZmNkNWExZmExODA2NGM4NzhkMjA3ZWY4ODkw By using this website, you agree with our Cookies Policy. Required fields are marked *. So the Collection Gives Facility for default sorting by using utility class Collections. It takes one set as a parameter and returns True if all of the elements of this set is present in the other set. YTFiYTcwZjNiZGRlNjgwMmI5N2E2ZjcxY2Q0NjhmMzBhNjk3Y2ZmYTZkMDI3 Create HashSet String strArr [] = { "P", "Q", "R" }; Set s = new HashSet (Arrays.asList (strArr)); Let us now count the number of elements in the above Set s.size () The following is an example to count the number of elements in a HashSet Example Live Demo The containsAll() method can determine whether a set is a subset of another set. Microsoft makes no warranties, express or implied, with respect to the information provided here. Login details for this Free course will be emailed to you. Note: it could come to a different order for everyone. 2.-HashSet doesnt allow duplicates. ZGZjZmQ3YTk3YzY5MDA2NDEyODA5Nzk0MjI1ODA1ODM2NjI2ZjJlNTMyZjIw Internally, HashSet stores its object using HashMap. ZjI0YmNmYzJmZGVhYzYxZmI0NzFlNTJmNzBhNjg1MDkyNzVhNWFjNjNhNzZk Returns a shallow copy of this HashSet instance: the elements themselves are not cloned. Song s2 = new Song(xx, mosin, 23, 343); Song s6 = new Song(ooo, yakoob, 23, 343); Gets the number of elements that are contained in a set. M2U0YzA3ZDFkYzAwZmExYTJlYzAyY2Q3ZDQ5YWM3MTliMmQ0MjQyNTdjNTBl thanks! HashSet size() Method in Java Higher() (Returns the least higher element), floor(), ceiling(), and other operations are also supported. Learn more. The HashSet class contains several constructors that allow the HashSet to be created. The constructors accessible in this class are as follows. Hello. A HashSet object's capacity automatically increases as elements are added to the object. NGNlNzBiNDI4YzU0ZjYxOGFjNTUzZmZhNTc0NjdiZjNmYmNkNGRiYzc2Yjc3 How alive is object agreement in spoken French? OWRkNjdjMDQ0MWUxZTBhMWM5MmY5MzI5MDJlMGE5MzQ3MGUzYTRjYTY0YTJk In this tutorial, we understand the concept of Hashset as in the definition of hashset, the syntax to create an hashset, constructors in hashset, methods in hashset, and programming examples for the creation of hashset, adding elements to a newly created hashset, removing the elements from an existing hashset, checking for an element in the hashset. HashSet applies the random order of the elements. In addition, the Set interface is implemented. . Two lists are regarded as equal in the preceding example if they have the same elements in the same order. On the other hand, the put() method is used by HashMap to store data. This website uses cookies to improve your experience. It uses HashMap internally. Basic example of C++ HashSet using {. HashSet in Java In the same way, the remove() method works. We may see various methods for removing an element here. The return type is a Spliterator. ==================Hash List=================== e2==null : e.equals(e2)). The set interface is implemented by the HashSet class, which has a hash table as backup and is an instance of HashMap. The hash table undergoes rehashing (internal data structures are rebuilt) when the number of entries in the hash table exceeds the product of the load factor and the current capacity. ZTc3MTY2Yjg3YWU5NjhkNmFiNGRhZDZmNGY0NTA4MjllZDkxMDVlNjcxNGQ1 This class implements the Set interface, backed by a hash table (actually a HashMap instance). July 2, 2023. Lets look at a simple HashSet example. Because the two lists are equal, they will both return the same hash when you use the hashCode() method on them. Sitemap. Comment *document.getElementById("comment").setAttribute( "id", "a97a966697a0041f4aa00f8d4d2acf9b" );document.getElementById("e9f84a7fd5").setAttribute( "id", "comment" ); Techndeck.com is a blog revolves around software development & testing technologies. The iterator() method is used to access the elements of a hash set. The goal is to remove the duplicate description and then adding the count of similar descriptions. The AbstractSet class implements Set interface, which extends Collection interface. The method clone() returns an object. If equals() and compareTo() are not consistent, i.e., equals should return true for two equal objects. Parameters: initialCapacity - the initial capacity of the hash table. remove()- Removes the requested element from the set with remove(). As a result, all of the values in the key-value combination will be the same. Search, insert, and remove actions; these operations take the same average time. Writing program with Hashset that show me This website uses cookies to improve your experience while you navigate through the website. quick and easy tutorial for java hashsets. Making statements based on opinion; back them up with references or personal experience. HashSets fundamental data structure is Hashtable. Java HashSet MWJiNTRmMDM4YjIyYWM1ODE0ZjBlZDlhODM5ZGZkNjM0NmYxNjMxNTBiMGIz Can you share your full code example please? MDFjMzYwOTNhZjZhM2E4YmI2M2Q3MjIwNDlhZDE2N2MwZjBhM2RhZDA1ZmUw But you haven't written "thousands lines" have you? Count the number of elements in a HashSet in Java The collection c members are utilized to initialize the hash set. Internally, HashSet uses HashMap to add entries. We can see that HashSet does not allow duplicate elements in this example. We have an exciting edition lined up for you, packed with valuable content and insightful articles. Out of these cookies, the cookies that are categorized as necessary are stored on your browser as they are essential for the working of basic functionalities of the website. YWI0OTY1NTFkNmFmNTQzM2NiMzczMGM0MTk1ZGI1MGQyYzkwMTVkZTcwNmE3 Its used to set the hash sets capacity to the given integer value capacity and the defined load factor. HashSet refers to a set, for instance {11, 12, 13, 14, 15, 16, 17}. AbstractCollection containsAll() Method in Java with Examples, List containsAll() method in Java with Examples, CopyOnWriteArrayList containsAll() method in Java, A-143, 9th Floor, Sovereign Corporate Tower, Sector-136, Noida, Uttar Pradesh - 201305, We use cookies to ensure you have the best browsing experience on our website. according to what it says on oracle website in this link (https://docs.oracle.com/javase/7/docs/api/java/util/HashSet.html), its the other way around (i.e. If this set already contains the element, the call leaves the set unchanged and returns false. TreeSet does not allow null objects and throws a NullPointerException because it compares keys using the compareTo() function, which throws java.lang.NullPointerException. { HashSet<String> set = new HashSet<String> (); set.add ("Welcome"); set.add ("To"); set.add ("Geeks"); set.add ("4"); set.add ("Geeks"); System.out.println ("HashSet: " + set); System.out.println ("The size of the set is: " + set.size ()); } } Output: HashSet: [4, Geeks, Welcome, To] The size of the set is: 4 Last Updated : 26 Nov, 2018

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