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 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());  }  } } 

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.