How to Add or Update Elements in a HashTable in Java?
In Java, HashTable is a pre-defined class of the collection framework. It is a part of the java.util package and is used to store the key-value pairs in the program. In this article, we will learn how to add and update elements in a HashTable in Java.
Pre-defined Classe to add and update elements in a HashTable
To add or update elements in a HashTable the pre-defined class is:
- HashTable: It is a pre-defined class and it can be used to add or update the elements into the HashMap using the HashTable.
Program to add and update elements in a HashTable in Java
Below is the code implementation to add or update elements in a HashTable.
Java
// Java program to add or update elements in a HashTable import java.util.Hashtable; import java.util.Map; public class GFGHashTableExample { public static void main(String[] args) { // create a HashTable named as hashTable Hashtable<String, String> hashTable = new Hashtable<>(); // adding elements hashTable.put( "key1" , "HTML" ); hashTable.put( "key2" , "CSS" ); hashTable.put( "key3" , "JavaScript" ); hashTable.put( "key4" , "ReactJs" ); // printing the elements before update System.out.println( "Original HashMap" ); for (Map.Entry<String, String> entry : hashTable.entrySet()) { System.out.println(entry.getKey() + ": " + entry.getValue()); } // updating an element hashTable.put( "key3" , "NodeJs" ); // Printing the elements after update System.out.println(); System.out.println( "Updated HashMap" ); for (Map.Entry<String, String> entry : hashTable.entrySet()) { System.out.println(entry.getKey() + ": " + entry.getValue()); } } } |
Output
Original HashMap key4: ReactJs key3: JavaScript key2: CSS key1: HTML Updated HashMap key4: ReactJs key3: NodeJs key2: CSS key1: HTML
Explanation of the Program:
- The above Java program demonstrates adding and updating elements in a Hashtable.
- We have created a Hashtable named
hashTable
and adds key-value pairs into it. - Then the original Hashtable is printed.
- After that, it updates the value associated with the key “key3” to “NodeJs” and prints the Hashtable again to show the changes.
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