Hashtable in Java

The Hashtable is a legacy implementation of HashMap. It provides a key-value store where the keys are hashed. HashMap performs better than Hashtable.

Key Properties of Hashtable

The Hashtable is synchronized, meaning it is thread-safe and can be shared between multiple threads.

Hashtable does not allow null keys or values. If you try to add null as a key or value, it will throw a NullPointerException.

public class _1a_Hashtable {  


    public static void main(String[] args) {  
        Hashtable<Integer, String> hashtable = new Hashtable<>();  
        hashtable.put(1, "One");  
        hashtable.put(2, "Two");  
        hashtable.put(3, "Three");  

        // Retrieve a value by its key  
        String value = hashtable.get(2);  
        System.out.println("Value for key 2: " + value);  

        // Remove a key-value pair  
        hashtable.remove(3);  

        // Check if a key exists  
        boolean containsKey = hashtable.containsKey(1);  
        System.out.println("Hashtable contains key 1: " + containsKey);  

        // Check if a value exists  
        boolean containsValue = hashtable.containsValue("Two");  
        System.out.println("Hashtable contains value 'Two': " + containsValue);  

        // Get the size of the hashtable  
        int size = hashtable.size();  
        System.out.println("Size of hashtable: " + size);  

        // Check if the hashtable is empty  
        boolean isEmpty = hashtable.isEmpty();  
        System.out.println("Is hashtable empty? " + isEmpty);  
    }
}