Are you confused about the difference between HashMap and Hashtable? You’re not alone. In fact, the two can often be mistaken for one another since they are both popular data structures used in Java to store key-value pairs on a hash table. There are many similarities between them at first glance such as their shared usage of hashing algorithms and methods of insertion, but there also lie several differences that may influence your choice when deciding which data structure to use for your particular programming needs. Keep reading to get an in-depth comparison of these two objects and hopefully gain more clarity regarding which direction is best suited for you!
What is HashMap?
HashMap is a data structure that stores key-value pairs. HashMap uses the hashing algorithm to generate a hash from the key, which is then used by HashMap to store and retrieve data quickly. HashMap has been designed for high performance, making it an efficient tool for accessing large datasets of key-value pairs. HashMap can also make it easier to access specific records in a large dataset by using the Hash Key associated with each record. Overall, HashMap is an incredibly powerful tool that provides quick access to large data sets while managing memory usage efficiently.
What is Hashtable?
Hashtable is a powerful data structure used to store keys and associated values in an efficient manner. Hashtable Hashtables are ideal for situations where inserting and retrieving elements need to be done quickly. Hashtables apply an algorithm known as a hash function to compute the indexes for each element, which helps speed up insertion and retrieval significantly. Hashtable provides great performance when dealing with large datasets, as the time complexity for look-up operations remains constant regardless of dataset size. This makes Hashtables an invaluable tool for various tasks related to data processing.
Difference Between HashMap and Hashtable
HashMap and Hashtable are two of the most important Java collections.
- HashMap and Hashtable offer users a way to store data in an organized manner and retrieve it quickly when needed. The primary difference between HashMap and Hashtable is the fact that HashMap allows a null key value, while Hashtable forbids null keys.
- HashMap also offers users synchronization while Hashtable does not. Additionally, Hashmap permits one null value for each key, whereas Hashtable does not permit any null values at all.
- Finally, the method of using an Iterator for handling elements is different for both; Hashtable uses Enumerators whereas HashMap uses Iterators.
Knowing the differences between these two collections provides users with the ability to use them efficiently and effectively in their programs.
Conclusion
Both HashMap and Hashtable classes are used to store data in key/value pairs. The main difference between HashMap and Hashtable is that HashMap is non-synchronized while Hashtable is synchronized. This means that multiple threads can access a HashMap at the same time without any issues. However, only one thread can access a Hashtable at a given time. If multiple threads try to access a synchronized hash table, they will be blocked until the first thread finishes accessing it. Another difference between HashMap and Hashtable is that the Iterator in the HashMap class is fail-fast while the enumerator for the Hashtable class is not fail-fast. This means that if one thread modifies a hashmap while another iterator tries to traverse over it, there’s a chance of getting an exception thrown. There isn’t such risk when using hashtables since they are synchronized.
