Get hold of all the important Java and Collections concepts with the Fundamentals of Java and Java Collections Course at a student-friendly price and become industry ready. One of the common interview questions is “What are differences between Hashtable and HashMap“.When I started using them, I used any of them irrespective of their differences.Afterward I found noticeable differences between them which can affect your performance of the application. close, link Split() String method in Java with examples. To successfully store and retrieve objects from a HashTable, the objects used as keys must implement the hashCode method and the equals method. Fail-fast iterator means if one thread is iterating over hashmap and other thread trying to modify hashmap structurally it will throw ConcurrentModification Exception and fail immediately. Yes, We can synchronized a HashMap also with the help of Collections.synchonizedMap(hashmap) so HashMap can be synchronized by. Sostanziale differenza sta nel fatto che HashTable è sincronizzata (synchronized), mentre l’HashMap no. HashMap and HashTable both are one of the most important classes of Java Collection framework. share | improve this … Parameters: HashMap: Hashtable: Synchronization. How to Use Enumeration to Display Elements of Hashtable in Java? HashMap implements Map  interface which maps a key to value. 1. Both HashMap and HashTable stores the data in key value pair and at the time storing data hashing is used to hash the key and the resulting hash code is used as the index at which the value is stored within the table. Hashmap vs Hashtable 1. J2SE vs J2ME vs J2EE….What’s the difference? 3. Factors HashMap Hashtable; Synchronization: java.util.HashMap methods is not synchronized, not thread safe and can’t be shared … http://docs.oracle.com/javase/6/docs/api/java/util/Hashtable.html: This article is compiled by Aditya Goel. Next Topic Java EnumSet (HashMap Here) HashMap, HashSet and HashTable: HashMap, HashSet and Hashtable usually store values in key value pair. Hashtable vs HashMap in Java Hashtable and HashMap are two hash based collection in Java and used to store objects as key value pair. HashMap was created later. But still, there are many differences between both these classes which we … HashMap is non synchronized. HashMap and HashTable both are one of the most important classes of Java Collection framework. jQuery(document).ready(function($) { edit Writing code in comment? HashMap is an advanced version and improvement on the Hashtable. Check if two arrays are permutations of each other. Hashtable vs HashMap. .Before we actually see differences, let me give you a brief introduction of both. It is not-thread safe and can’t be shared between many threads without proper synchronization code whereas Hashtable is synchronized. Please go through core java interview questions for more interview questions. $.post('https://java2blog.com/wp-admin/admin-ajax.php', {action: 'mts_view_count', id: '404'}); Why HashTable doesn’t allow null and HashMap does? Hashtable implements Map interface which maps key to value. Post Category: Java; Post Comments: 0 Comments; Even though HashTable and HashMap both are data-structure based upon Hashing and implementation of Map Interface, there are many difference among them. http://docs.oracle.com/javase/6/docs/api/java/util/Hashtable.html: HashTable compute() method in Java with Examples, Hashtable keySet() Method in Java with Examples. Duplicate keys are not allowed and the null key is not allowed. 2) Hashtable and HashMap both are a hash based collection and works on the principle of hashing. Structurally modification means inserting or deleting elements that can change the structure of map. But there are many differences between HashMap and Hashtable classes that are given below. HashSet implements Set, Cloneable, Serializable, Iterable and Collection interfaces. Are you preparing for an interview for a Java profession? HashTable vs HashMap in Java. When using a Hashtable or HashMap, we specify an object that is used as a key, and the value that you want linked to that key. Some important points need to be discussed. Stores : In HashMap we store a key-value pair. Since null is not an object, it can’t implement these methods. It is not-thread safe and can’t be shared between many threads without proper synchronization code whereas Hashtable is synchronized. Don’t stop learning now. While the Hashtable was part of the initial Java release over two decades ago, the HashMap is the correct key-value store to use today. 1) Both Hashtable and HashMap implements java.util.Map interface. Java HashMap is a hash table based implementation of Map interface. HashMap is generally preferred over HashTable if thread synchronization is not needed. acknowledge that you have read and understood our, GATE CS Original Papers and Official Keys, ISRO CS Original Papers and Official Keys, ISRO CS Syllabus for Scientist/Engineer Exam, Differences between HashMap and HashTable in Java, HashTable forEach() method in Java with Examples, Hashtable computeIfAbsent() method in Java with Examples, HashTable putIfAbsent() method in Java with Examples, Differences between TreeMap, HashMap and LinkedHashMap in Java. Despite being hash based and similar in functionality there are a significant difference between Hashtable and HashMap and without understanding those difference if you use Hashtable in place of HashMap than you may run into series of subtle programs … Implementation: HashMap implements Map, Cloneable, and Serializable interface es. Both HashMap and HashTable stores the data in key value pair and at the time storing data hashing is used to hash the key and the resulting hash code is used as the index at which the value is stored within the table. Different ways for Integer to String Conversions In Java, Write Interview Difference between Hashtable and HashMap in java, //not allowed and will throw NullPointer exception at run time, Due to theadSafe and Synchronized,it is often slower than HashMap, In single threaded environment, it is much faster than Hashtable.So if you do not work in multi thread environment ,then hashMap is recommended, enumeration in hashtable is not fail fast, It extends Dictionary class which is quite old, You can use ConcurrentHashMap for multi thread environment, Can we call run() method directly to start a new thread, Object level locking vs Class level locking, Java 8 Lamba Expression examples using Comparator, How to sort HashMap in java by keys and values, Java Collections interview questions and answers, Difference between Iterator and ListIterator in java, How to remove duplicates from ArrayList in java, How to iterate over Map or HashMap in java, Convert LocalDateTime to Timestamp in Java, Java program to find first and last digit of a number. We use cookies to ensure you have the best browsing experience on our website. It is synchronized and thread-safe. It is not synchronized and is not thread-safe. If you are talking about the Hashtable and HashMap included with the Java SDK, there is definitely a performance difference, as HashMap doesn't have to use the synchronized blocks, which have an overhead. Experience. As per pst's request, here is some reading about synchronized performance and here is something a bit more recent, regarding Java 1.4 vs Java 6 on one machine. Differences between HashMap and HashTable in Java Last Updated: 08-07-2020. }); Save my name, email, and website in this browser for the next time I comment. Both are using hashing technique to store unique keys. Internal Working of HashMap Hashtable Vs HashMap HashMap Vs HashSet Comparable Comparator Comparator Vs Comparable Multithreading Thread Process vs thread Join Daemon thread Sleep Can we start a thread twice in java Can we call run() method directly to start a new thread wait, notify and notifyAll print even and odd numbers Sleep vs wait This is a part … 3) Hashtable and HashMap both provide constant time performance for put and get method if objects are distributed uniformly across bucket. When using a Hashtable or HashMap, we specify an object that is used as a key, and the value that you want linked to that key. The key is then hashed, and the resulting hash code is used as the index at which the value is stored within the table. HashMap and Hashtable store key/value pairs in a hash table. It creates a collection that uses a hash table for storage. 2. HashSet is a Set.