Notify me of follow-up comments by email. The Hashtable class implements the Map interface and extends the Dictionary class and does not guarantee the order of its elements. My name is RahimV and I have over 16 years of experience in designing and developing Java applications. HashMap, the Hashtable is synchronized. Hope it helps you. All the structure of the hashtable itself is copied, but the keys and values are not cloned. There are few more differences between HashMap and Hashtable class, you can read them in detail at: Difference between HashMap and Hashtable. I tried Hashtable – it allows to put null keys as well as null values ?? The Hashtable class provides several constructors using which we can create new objects of the hashtable. Required fields are marked *, Copyright © 2012 – 2020 BeginnersBook . import java.util. The Hashtable containsValue method is similar to the contains method in functionality. The Hashtable put method maps given key with the given value in the hashtable. The below given additional Hashtable examples will help you understand the concepts in more detail. If the key does not exist, it returns null. That’s why you were good to use “” as key and value. If the key exists, it simply returns the value associated with the given key. In Java version 2, the Hashtable class was rewritten to implement the Map interface and that made it a member of the Java Collection Framework. The Hashtable elements method returns an enumeration of all the values contained in this hashtable object. Returns false if the value isn’t found. Your email address will not be published. internally contains buckets in which it stores the key/value pairs It is necessary for anyone to be clear with the working of a hash table before moving on to the implementation aspect. The returned Set is a view that is backed by the original Hashtable object. If we look at the source code of the Hashtable class, we can see that the containsValue method calls the contains method. Sitemap. It returns true if the given value is mapped to one or more keys in the hashtable, false otherwise. Hashtable in Java is an implementation of the Map interface. import java.util. The Hashtable keys method returns an enumeration of the keys contained in this hashtable object. 5) Enumeration keys(): Returns an enumeration of the keys contained in the hash table. This operation is more expensive than the containsKey method. Note that this method is identical in functionality to containsValue, (which is part of the Map interface in the collections framework). HashTable in Java Example | Java HashTable Tutorial HashTable in Java. If you want to create a new mapping if the key does not exist, but do not want to replace the value if the key already exists then use the putIfAbsent method. Hashtable is similar to HashMap except it is synchronized. It returns zero if the hashtable is empty. Why is it not printing in 1,2,3,4,5, order but in 4,3,2,1,5? The Hashtable putAll method copies all the mappings of the specified map to this hashtable object. If you want to create a new hashtable object with custom initial capacity and load factor, you can use the below given overloaded constructor. If the specified key was mapped to any value, it replaces the old value with new value and returns the old value. The below given are some of the important methods of the Hashtable class in Java. *; public class HashTableDemo { public static void main(String args[]) { // … Could you please look the code. hashtable.put(“K”, “kan”); My goal is to provide high quality but simple to understand Java tutorials and examples for free. If you want to remove the mapping if and only if the specified key is mapped to the specified value, use the below given overloaded remove method. The new hashtable object will have the initial capacity enough to hold the specified map entries and the default load factor of 0.75. The new object has a default initial capacity of 11 and a default load factor of 0.75. To successfully store and retrieve objects from a hashtable, the objects used as keys must implement the hashCode … Hashtable implements Serializable, Cloneable, Map interfaces and extends Dictionary.The direct subclasses are Properties, UIDefaults.. Constructors: In order to create a Hashtable, we need to import it from java.util.Hashtable.There are various ways in which we can create a Hashtable. Then using this enumeration, we print the key-value pairs from the HashTable.