Hashtable java

1. What is a Hashtable in Java?
2. Why Hashtable is used in Java?
3. What is the difference between HashMap and Hashtable?
4. Is Hashtable a Java class?
5. What is Hashtable data structure?
6. What is the use of hash table?
7. What are interfaces for in Java?
8. How is Hashtable synchronized in Java?
9. What is difference between Hashtable and ConcurrentHashMap in Java?
10. Is map a Hashtable?
11. How does Hashtable work internally in Java?
12. Can HashTable contain duplicate keys?
13. What is load factor HashTable?

What is a Hashtable in Java?

Hashtable was part of the original java. util and is a concrete implementation of a Dictionary. ... Like HashMap, Hashtable stores key/value pairs in a hash table. When using a Hashtable, you specify an object that is used as a key, and the value that you want linked to that key.

Why Hashtable is used in Java?

The Hashtable class implements a hash table, which maps keys to values. Any non-null object can be used as a key or as a value. To successfully store and retrieve objects from a hashtable, the objects used as keys must implement the hashCode method and the equals method.

What is the difference between HashMap and Hashtable?

HashMap is non-synchronized. It is not thread-safe and can't be shared between many threads without proper synchronization code whereas Hashtable is synchronized. ... HashMap allows one null key and multiple null values whereas Hashtable doesn't allow any null key or value.

Is Hashtable a Java class?

Java Hashtable class. Java Hashtable class implements a hashtable, which maps keys to values. It inherits Dictionary class and implements the Map interface.

What is Hashtable data structure?

Hash Table is a data structure which stores data in an associative manner. In a hash table, data is stored in an array format, where each data value has its own unique index value. ... Thus, it becomes a data structure in which insertion and search operations are very fast irrespective of the size of the data.

What is the use of hash table?

In computing, a hash table (hash map) is a data structure that implements an associative array abstract data type, a structure that can map keys to values. A hash table uses a hash function to compute an index, also called a hash code, into an array of buckets or slots, from which the desired value can be found.

What are interfaces for in Java?

In Java, an interface is an abstract type that contains a collection of methods and constant variables. It is one of the core concepts in Java and is used to achieve abstraction, polymorphism and multiple inheritances. We can implement an interface in a Java class by using the implements keyword.

How is Hashtable synchronized in Java?

Hashtable is synchronized. It ensures that no more than one thread can access the Hashtable at a given moment of time. The thread which works on Hashtable acquires a lock on it to make the other threads wait till its work gets completed. 2) HashMap allows one null key and any number of null values.

What is difference between Hashtable and ConcurrentHashMap in Java?

Hashtable is belongs to the Collection framework; ConcurrentHashMap belongs to the Executor framework. Hashtable uses single lock for whole data. ConcurrentHashMap uses multiple locks on segment level (16 by default) instead of object level i.e. whole Map . ConcurrentHashMap locking is applied only for updates.

Is map a Hashtable?

is it a map or a hashtable? Yes. The static, compile time type of the reference is Map . As others have already pointed out, it's an interface.

How does Hashtable work internally in Java?

Hashtable internally contains buckets in which it stores the key/value pairs. The Hashtable uses the key's hashcode to determine to which bucket the key/value pair should map. The function to get bucket location from Key's hashcode is called hash function. ... To resolve collisions, hashtable uses an array of lists.

Can HashTable contain duplicate keys?

1 Answer. You can't add duplicate keys to hashtables, because hashtables by design can only contain unique keys. If you need to store duplicate key/value pairs, use arrays.

What is load factor HashTable?

The load factor is a measure of how full the hash table is allowed to get before its capacity is automatically increased.