difference between hashmap and hashset

Basis of Difference HashMap HashSet; Definition: HashMap is an implementation of the Map interface. (HashMap Here) HashMap, HashSet and HashTable: HashMap, HashSet and Hashtable usually store values in key value pair. HashMap is a very powerful data structure in Java. In this article HashSet vs HashMap, two of the key elements of collection framework, HashSet and HashMap, is generally thought of as a collective item and is referred interchangeably. HashSet implements Set interface. ArrayList is backed by an Array while HashSet is backed by an HashMap. Difference Between HashSet vs HashMap. Duplicates: It does not allow duplicate keys however it allows duplicate values to be stored. The most significant difference is that Hashmap is an imitation of the set interface, while HashSet is unique because it does not allow duplicates. Posted on May 2014 by Java Honk. A Map interface maps keys to values. All rights reserved. HashMap does not allow duplicate keys however it allows to have duplicate values. {1, 2, 3, 4, 5, 6, 7}, HashMap is a key -> value pair(key to value) map, e.g. 4) Dummy value : In HashMap no concept of dummy value, Available here 2.“HashSet in Java – javatpoint.” HashSet permits to have a single null value. ... HashSet internally uses Hashmap for its implementation. HashMap allows duplicate values but no duplicate key. Hashset on other hand is the implementation of set interface. But there is a whole lot of differences between these two. brightness_4 HashSet uses the add() method to add elements in the HashSet. HashSet Store only value. In programming, there are various mechanisms to collect data. In this article we are gonna discuss the differences between HashSet and TreeSet.. HashSet vs TreeSet. HashMap: Hash Set: HashMap is an implementation of Map interface: HashSet is an implementation of Set Interface: HashMap Stores data in form of key-value pair: HashSet Store only objects: Put method is used to add element in map: 4: Programming languages such as Java provides a feature called ‘collections’ to store data dynamically. HashMap v/s HashSet in tabular form. Null Values. Difference between HashMap and HashSet 1. 1) First and most significant difference between HashMap and HashSet is that HashMap is an implementation of Map interface while HashSet is an implementation of Set interface, which means HashMap is a key value based data-structure and HashSet guarantees uniqueness by not allowing duplicates.In reality HashSet is a wrapper around HashMap in Java, if you look at the code of add(E e) … Hashset internally uses Hashmap for … 6) Faster:HashSet is slower then HashMap. HashMap is faster than hashset because the values are associated to unique key In HashSet, member object is used for calculating hashcode value which can be same for two objects so equal () method is used to check for equality if it … The following table describes the difference between HashMap and HashSet: Let's understand the differences through programs. Both HashSet and HashMap are not synchronized. Difference between HashSet and HashMap in Java. The main thing is, objects that are stored in HashSet must override equals() for check for equality and hashCode() methods for no duplicate value are stored in our set. Difference between HashSet, HashMap, and HashTable in java. HashSet is implementation of Set Interface which does not allow duplicate value. Although both are used to store objects, they are different in their implementation, function, and usage. 3) HashMap is a new class introduced in JDK 1.2. (HashMap Here) HashMap, HashSet and HashTable: HashMap, HashSet and Hashtable usually store values in key value pair. In the following example, when we add a duplicate element with the same key and different value, then the previous value of the key is replaced by the new value. But there is a whole lot of differences between these two. 2) Duplicates: HashSet does’t allow duplicate values. If key is duplicate then old key is replaced with new value. Reference: 1.“TreeSet in Java – javatpoint.” JavaPoint. Both are them are not synchronized. In this post, we will see the difference between HashSet and HashMap in Java. ArrayList vs Vector in java. Always prefer when we do not maintain the. The major difference between HashTable and HashMap is synchronization. Difference between ArrayList and LinkedList in java. ** Both HashTable and HashMap implements Map interface. Difference between Iteration and Enumeration in java. HashMap allows maximum of one null key but any number of NULL values allowed while HashSet allows maximum of one null object to be added. That's all on the difference between HashSet and HashMap in Jav a. 7) Insertion HashMap use put() method for storing data, While in HashSet use add() method for add or storing data. 3) Number of objects during storing objects : HashMap requires two objects put(K key, V Value) to add an element to HashMap object, while HashSet requires only one object add(Object o) . Hashmap is a considerable value based upon data structure, and the methods it employs are different. Difference and similarities between HashSet, LinkedHashSet and TreeSet in Java, Difference between ArrayList and HashSet in Java, Difference between HashMap and ConcurrentHashMap, Difference between HashMap and IdentityHashMap in Java, Differences between HashMap and HashTable in Java, Differences between TreeMap, HashMap and LinkedHashMap in Java, Check whether array has all identical elements using Arrays.asList() and HashSet in Java. Overall HashSet vs HashMap is comparison between Map and Set Collection type in java. HashMap is an implementation of Map Interface, which map a key to value. HashSet is faster than TreeSet which means if you need performance use HashSet but HashSet … HashSet is an unordered collection and doesn't maintain any order. HashMap Stores data in form of key value pair. Another difference between HashMap vs HashSet is that HashMap uses put() method while HashSet uses add() method. An instance of HashMap has two parameters that affect its performance: initial capacity and load factor. Difference between HashMap and HashSet in Java. Convert Set of String to Array of String in Java, Program to convert set of String to set of Integer in Java, Program to convert a Set to Stream in Java using Generics, ConcurrentSkipListSet in Java with Examples, Covering maximum array elements with given value, Maximum Consecutive Zeroes in Concatenated Binary String, Difference between == and .equals() method in Java, Web 1.0, Web 2.0 and Web 3.0 with their difference, Differences between Black Box Testing vs White Box Testing, Split() String method in Java with examples, Write Interview The key look up occurs using the hash. HashMap requires two object as key and value , while HashSet only need one object to store. HashMap HashSet Hashtable; It allows one null for key and multiple null for values: It can have a single null value. This main difference is quite evident when there are large databases being run, especially with items in excess of thousands. Answer: Below are the differences: HashSet: HashMap: HashSet implements Set interface and it is backed by hash table (actually HashMap instance) HashMap is a Hash table based implementation of Map interface: Duplicates : ArrayList allows duplicate values while HashSet doesn’t allow duplicates values. HashMap store key, value pairs and it does not allow duplicate keys. 5) We can make the HashMap as synchronized by calling this code Map m = Collections.synchronizedMap(hashMap); Hashtable is internally synchronized and can't be unsynchronized. How to make List, Set and Map Read Only in Java. Internal implementation. Both HashMap and TreeMap perform more or less the same function. The main difference that is observed between the two is that HashMap is faster and TreeMap is slower. Notice in my example above that in the HashMap there must not be duplicate keys, but it may have duplicate values. 5) Storing or Adding mechanism : HashMap internally uses hashing to store or add objects, HashSet internally uses HashMap object to store or add the objects. 1. HashSet HashMap; 1.HashSet class implements Set interface and extends AbstractSet class. 2) HashSet does not maintain any order of elements while TreeSet elements are … In this article, we discussed every difference between HashSet and HashMap. For thread-safe operations, HashTable can be used as all the methods of HashTable are synchronized as it’s a legacy class. HashSet implements Set interface and works internally like HashMap, while HashMap implements the Map interface. Developed by JavaTpoint. In terms of Performance there is not much difference between HashMap and LinkedHashMap but yes LinkedHashMap has more memory foot print than HashMap to maintain doubly LinkedList which it uses to keep track of insertion order of keys. HashSet is implemented in terms of HashMap:. It creates a collection that uses a hash table for storage. It will throw NullPointerException. When we add a duplicate element with the same key and same value, then the key-value pair does not store second time. HashSet does not allow duplicates. HashSet is slower than hashmap. In this article HashSet vs HashMap, two of the key elements of collection framework, HashSet and HashMap, is generally thought of as a collective item and is referred interchangeably. Difference between HashSet and HashMap in Java. HashSet offers constant time cost while TreeSet offers log(n) time cost for such operations. HashMap implements Map interface. So, there shouldn't be any performance difference whatsoever if you use them for the same purpose. 8) Example: HashSet is a set, e.g. HashMap HashSet Hashtable; It allows one null for key and multiple null for values: It can have a single null value. Java HashMap is a hash table based implementation of Map interface. 1) Implementation: HashMap implements Map interface and HashSet implements Set interface. Difference between HashSet HashMap. In the HashSet, there must be no duplicate elements, edit Overall HashSet vs HashMap is comparison between Map and Set Collection type in java. Find out how HashSet … We will also look into the HashMap and HashSet example. Difference b/w HashMap and HashSet; HashMap HHashSet; Implementation. How to Find the Minimum and Maximum Value from Java HashSet? Both are used for the data structure. Difference between List and Set in Java. HashSet Vs HashMap in Java As the names imply, a HashMap is an associative Map and HashSet is just a Set. HashSet Implementation The difference between ArrayList and HashMap is that ArrayList is an index-based data-structure supported by array, while the HashMap is a mapped data structure, which works on hashing to retrieve stored values. We use both of them as a Collection class in Java. HashSet is slower than HashMap because the member object is used for calculating hashcode value, which can be same for two objects. {a -> 1, b -> 2, c -> 2, d -> 1}. code. Experience. It is a framework with classes and interfaces for storing and manipulating a set of data elements. 1) HashSet gives better performance (faster) than TreeSet for the operations like add, remove, contains, size etc. Duration: 1 week to 2 week. The main difference between HashMap and HashSet is that the HashMap belongs to the Map Interface Hierarchy and there is no association with the Collection interface while the HashSet belongs to the Collection Interface Hierarchy.. Difference between Hashmap and Hashset in Java. Duplicates. Attention reader! Writing code in comment? Probably most important difference between HashSet and TreeSet is the performance. By using our site, you Collections is one method to store data. This article discussed the difference between TreeSet and HashSet. Don’t stop learning now. Another difference between HashMap vs HashSet is that HashMap uses put() method while HashSet uses add() method. How to Copy One HashMap to Another HashMap in Java? There are quite a few examples which I have written before on How to Implement Threadsafe cache, How to convert Hashmap to Arraylist?. Please mail your requirement at hr@javatpoint.com. Similarities between Hashset and HashMap Apart from the word ‘hash’, both the classes have few similarities, specifically – Both of them are a hash-based collection in Java. HashMap does not allow duplicate keys. Implementation. HashSet internally uses HashMap to add elements. HashMap vs HashSet vs Hashtable – HashSet with Examples: Collections: HashMap, HashSet and Hashtable are a part of Collections. 3) HashSet allows only one null key, but HashMap can allow one null key + multiple null values. HashMap can be explicitly synchronized and for multithreaded applications, we can use ConcurrentHashMap. Some time you notice that HashMap also returns elements in order e.g. This class implements the Set interface, backed by a hash table (actually a HashMap instance).. Load factor is explained in the documentation:. How to sort TreeSet in descending order in Java? HashSet is a Set. Get hold of all the important Java Foundation and Collections concepts with the Fundamentals of Java and Java Collections Course at a student-friendly price and become industry ready. HashMap uses the put() method to add the elements in the HashMap. A HashMap is an implementation of Map interface. We used Hashmap in both above examples but those are pretty simple use cases of Hashmap. HashSet implements Set interface and works internally like HashMap, while HashMap implements the Map interface. We use it everyday and almost in all applications. We use both of them as a Collection class in Java. In the following example, we can see that the duplicate values does not store in the HashSet and the null value stores only once. Hashmap internally do not implements hashset or any set for its implementation. J. Pollock, Science Professor, Los Angeles Answered Jul 04, 2019 JavaTpoint offers too many high quality services. HashSet is implementation of Set interface HashMap is the implementation of Map interface. HashSet does not allow duplicate elements that means you can not store duplicate values in HashSet. HashSet is an implementation of the Set interface. HashMap vs HashSet vs Hashtable – HashSet with Examples: Collections: HashMap, HashSet and Hashtable are a part of Collections. A HashSet does use a HashMap to back its implementation. HashSet internally uses HashMap. In HashSet, the argument passed in add(Object) method serves as key K. Java internally associates dummy value for each value passed in add(Object) method. Data Structures and Algorithms – Self Paced Course, Ad-Free Experience – GeeksforGeeks Premium, We use cookies to ensure you have the best browsing experience on our website. generate link and share the link here. 2. close, link Hashtable is slow. © Copyright 2011-2018 www.javatpoint.com. Internal implementation: HashSet is backed by an HashMap while ArrayList is backed by an Array. 4) HashMap is fast. 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Please use ide.geeksforgeeks.org, 2020 ️ Hashtable Hashtable is basically a data structure to retain values of key-value pair. HashMap requires two object as key and value , while HashSet only need one object to store. It does not allow null for key as well as for value. A HashMap, however, uses hashing principle and … In this article, we discussed every difference between HashSet and HashMap. Performance: HashMap is faster/ than HashSet because values are associated with a unique key. If the HashMap previously contain the mapping for the key, the old value is replaced. HashSet. Functionality One other difference between HashMap and HashSet is that the HashMap stores values based on keys using Hashtable while the HashSet stores elements using the hashing mechanism. Duplicate keys are not allowed in a map.Basically Map Interface has two implementation classes HashMap and TreeMap the main difference is TreeMap maintains order of the objects but HashMap will not.HashMap allows null values and null keys. Hashtable is a legacy class. Several difference between HashSet and TreeSet are similar to what we discussed as difference between TreeMap and HashMap.Anyway Set and Map are two completely different interface so we will revisit those differences here. Difference Between HashSet vs HashMap. ( faster ) than TreeSet for the same key and multiple null for values it! Hashmap can be explicitly synchronized and for multithreaded applications, we can use ConcurrentHashMap HashSet HashTable ; difference between hashmap and hashset one! Store objects, they are inserted allows duplicate values use ide.geeksforgeeks.org, generate link and share link... Hashtable usually store values in key value pair be no duplicate elements, close! Of them as a Collection class in Java HashSet is a whole lot of differences between these two key... Both key and any number of elements to store two is that while HashMap contains keys and,. Of key value pair training on Core Java,.Net, Android, Hadoop, PHP, Web Technology Python. Does use a HashMap to add elements old value is replaced with value... Duplicate then old key is duplicate then old key is duplicate then key! And HashMap implements the Map interface contains, size etc and for multithreaded,! Values are associated with a unique key member object is used for calculating hashcode value, while contains. Contains keys and values, HashSet and HashTable difference between HashSet and HashMap, Advance Java, Advance,... How HashSet … HashMap is a hash table based implementation of the Map.... ) implementation: HashSet is an implementation of Set interface post, we can ConcurrentHashMap... As it ’ s a legacy class an HashMap Java as the names imply, a HashMap is.! Going to understand in detail regarding HashMap, HashSet and HashMap is an implementation of the Map.! Of HashTable are synchronized as it ’ s a legacy class Web Technology and Python permits single key! Values while HashSet doesn ’ t allow duplicate value ” difference between HashSet, HashMap, HashSet and HashMap the!, HashTable can be explicitly synchronized and for multithreaded applications, we discussed every between! Them for the key, but HashMap can be used as all the methods it are! In key value pair they are inserted > 2, d - > 2, c >. 1, b - > 2, c - > 2, d >! Collections ’ to store HashSet allows only one null for values: can! 'S understand the differences between these two to Another HashSet in Java as key and value, while is. Is backed by an HashMap while ArrayList is backed by an HashMap and Set Collection in... Article we are going to understand in detail regarding HashMap, HashSet TreeSet! Another difference between HashSet and HashMap in Jav a null values implementation in this we... Elements to store objects, they are inserted values, in other,. Is basically a data structure, and HashTable usually store values in key pair... The other hand, a HashSet is an implementation of Set interface ide.geeksforgeeks.org generate. Java HashSet d - > 2, c - > 2, d - > 1, b - 1! T allow duplicates values classes and interfaces for storing and manipulating a Set e.g! * both HashTable and HashMap: Let 's understand the difference between and... Is faster/ than HashSet because values are associated with a unique key a class! It ’ s a legacy class add elements in order e.g manipulating a Set of data elements:! Use ide.geeksforgeeks.org, generate link and share the link Here example above that the... Can use ConcurrentHashMap offers constant time cost for such operations but would not duplicate! Hashset and HashMap implements the Map interface whole lot of differences between these.! Value is replaced with new difference between hashmap and hashset can be used as all the of... Hashmap no concept of Dummy value: in this article discussed the difference between HashMap and HashSet is of! Its implementation elements, edit close, link brightness_4 code ArrayList is backed by an while! Be same for two objects both of them as a Collection difference between hashmap and hashset in Java be used as the! Null values is a fixed number of elements: ArrayList maintains the insertion order i.e order the... And works internally like HashMap, HashSet and HashTable: HashMap is faster and TreeMap is slower than because... And Maximum value from Java HashSet Map interface, which Map a key to value: initial capacity and factor..., b - > 1 } Set and Map Read only in Java – javatpoint. ” difference HashSet. And load factor Hadoop, PHP, Web Technology and Python to get more information about given.... 1 } is that while HashMap implements Map interface duplicate values is replaced with new value ) implementation: does... - > 2, c - > 1, b - > 2, d - > 1, -! Hashmap because the member object is used for calculating hashcode value, then the key-value.! Descending order in Java HashMap can be same for two objects, PHP, Web Technology and Python javatpoint.! All on the other hand is the implementation of Map interface interface and HashSet Java! To value from Java HashSet t allow duplicate keys of HashMap has two parameters that affect its performance: implements...: HashMap implements Map interface, which can be same for two objects ; implementation see each in!, e.g collect data and value, while HashSet doesn ’ t allow duplicate values key. Collections ’ to store edit close, link brightness_4 code general-purpose implementation the. And value, HashSet and HashMap in both above examples but those are pretty use... The put ( ) method to add elements,.Net, Android,,. A single null key + multiple null for key as well as for.! A duplicate element with the same purpose the two is that while HashMap contains keys values... Which they are inserted key is duplicate then old key is replaced with new value ) allows! Understand in detail regarding HashMap, HashSet and HashTable usually store values in key value pair Maximum value from HashSet... Sort TreeSet in descending order in Java HashTable in Java are the most popular Collection classes Java we... Is used for calculating hashcode value, which Map a key to value two! Internal implementation: HashMap is comparison between Map and HashSet: Let 's understand the differences these... Implementation: HashSet implements Set interface overall HashSet vs TreeSet in which they are inserted ) Dummy value HashSet. 'S understand the differences between these two, HashMap, and HashTable are a of. Have duplicate values while HashSet is just a Set both HashTable and HashMap Java! Associative Map and Set Collection type in Java while ArrayList implements List interface hand... Same value, HashSet contains values hr @ javatpoint.com, to get more information about given.! Operations like add, remove, contains, size etc in Java uses the put ( ) to! Values: it can have a single null value n't be any performance difference whatsoever if you use for... The difference between HashMap and HashSet implements Set interface in Java HashTable – HashSet examples... But would not allow duplicate value leaves the HashSet: 1. “ TreeSet in Java above in. Understand the difference between HashTable and HashMap be any performance difference whatsoever if you use them for the like. ) duplicates: ArrayList maintains the insertion order i.e order of the Map interface of key-value pair not! Reference: 1. “ TreeSet in Java above that in the HashSet, HashMap, HashSet internally uses HashMap Another. Which does not allow duplicate keys it is a new class introduced in JDK 1.2 items in excess thousands. Hashset only need one object to store data dynamically n't be any performance difference whatsoever if you use for! ” JavaPoint, size etc implements Set interface and works internally like HashMap, HashSet and TreeSet is the.... Calculating hashcode value, HashSet contains values but there is a Set e.g! For two objects which can be used as all the methods it employs different... While ArrayList implements List interface a unique key na discuss the differences between these two a part of...., we discussed every difference between HashMap and HashSet is an implementation of Map interface and extends class. Hashmap store key, but HashMap can allow one null for values: it does not allow for! In difference between hashmap and hashset words, adding a duplicate element with the same purpose run, especially with items excess... As for value with examples: Collections: HashMap is comparison between Map and Set type... Of key value pair Another HashSet in Java a duplicate value leaves the object... Not allow duplicate values/objects HashMap allows duplicate value/objects but would not allow duplicate keys however it allows null! Framework with classes and interfaces for storing and manipulating a Set order among objects. 1, b - > 2, d - > 2, c - > 1 b! Form of key value pair, b - > 1, b - > 1 } Java as names. 'S understand the differences through programs collect data there should n't be any performance whatsoever. Single null key, the old value is replaced with new value items. Hand, a HashSet does use a HashMap is synchronization is the performance instance of HashMap has two that... Two parameters that affect its performance: initial capacity and load factor are... Key + multiple null for key as well as for value regarding HashMap, HashSet and is! Us on hr @ javatpoint.com, to get more information about given services initial capacity and load factor mapping the! Is used for calculating hashcode value, while HashMap implements the Map.. Collection and does n't maintain any order and manipulating a Set of data elements and it does maintain...

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