What is enumeration in Hashtable in Java?
Hashtable class implements a hash table, which maps keys to values. We can obtain all keys and values respectively as an Enumeration object using Enumeration methods like hasMoreElements() and nextElement() we can read all keys and values corresponding to a Hashtable. Example 1: Java.
What is Hashtable with example 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 a Hashtable Java?
A Hashtable is an array of a list. Each list is known as a bucket. The position of the bucket is identified by calling the hashcode() method. A Hashtable contains values based on the key. Java Hashtable class contains unique elements.
How do I iterate through a Hashtable?
There are various ways by which we can iterate through the HashTable which are as follows:
- Using Enumeration Interface.
- Using keySet() method of Map and Enhance for loop.
- Using keySet() method of Map and Iterator Interface.
- Using entrySet() method of Map and enhanced for loop.
What is enumeration in Java?
Enumeration means a list of named constant. In Java, enumeration defines a class type. An Enumeration can have constructors, methods and instance variables. It is created using enum keyword. Enumeration variables are used and declared in much a same way as you do a primitive variable.
What is key enumeration?
Specifies key codes and modifiers. This enumeration has a FlagsAttribute attribute that allows a bitwise combination of its member values.
Is HashMap and Hashtable same?
Though both Hashtable and HashMap are data-structure based upon hashing and implementation of Map interface, the main difference between them is that HashMap is not thread-safe but Hashtable is thread-safe. Another difference is HashMap allows one null key and null values but Hashtable doesn’t allow null key or values.
Where are hash tables used?
Hash tables are commonly used to implement many types of in-memory tables. They are used to implement associative arrays (arrays whose indices are arbitrary strings or other complicated objects), especially in interpreted programming languages like Ruby, Python, and PHP.
How do I find the size of a hash table?
size() method of Hashtable class is used to get the size of the table which refers to the number of the key-value pair or mappings in the Table.
How to use enumeration to display elements of hashtable in Java?
How to Use Enumeration to Display Elements of Hashtable in Java? 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.
How to read all values from hashtable in Java?
By calling keys () method, we can get all keys as Enumeration object. By using Enumeration methods like hasMoreElements () and nextElement () we can read all values from Hashtable.?
What are the methods of enumeration in Java?
Methods in Enumeration in Java: values (): It returns an array that contains a list of the enumeration constants. Declaration : public static enum-type [] values (); Here, enum-type is the type of the enumeration. valueOf (String str): It returns the enumeration constant whose value corresponds to the string passed in str.
What is the use of enum in Java with example?
Every constant holds an object of the corresponding enum. Java enum is very efficient compared to C Language enum because in C Language enum contains only constants but in java, an enum can contain constants along with other codes like constructors, methods, etc. It returns an array that contains a list of the enumeration constants.