Developers & Programmers Interview

Java Question(s) & Actual Evaluation

* Please note that the following answer(s) are just sample answers from one of our candidates. It doesn't mean that it's the correct or wrong answer.
Please refer to the evaluation for more insight.

Classification: Developers & Programmers

Topic(s): Java

Interview Question:

Can you explain the difference between HashMap and HashTable in Java?

Candidate's Answer:

HashMap and Hash Table are both key value storage Classes, Hash table is Synchronized providing thread safety. HashMap is non synchronized making it fast for single threaded task. Hash table doesn't allow any null keys or values, whereas HashMap allows. HashMap allows to have one null key and several null values.

Evaluation:

Your answer is mostly correct, as you correctly highlighted the main differences between HashMap and HashTable in Java.

HashMap and HashTable are both classes that implement the Map interface in Java and store key-value pairs. The main difference between the two lies in their synchronization behavior. HashTable is synchronized, which means it is thread-safe and can be accessed by multiple threads concurrently without any issues. On the other hand, HashMap is not synchronized, making it faster for single-threaded operations but not suitable for use in multi-threaded environments without external synchronization.

Additionally, HashTable does not allow null keys or values, whereas HashMap allows one null key and multiple null values.

To improve your answer, you could elaborate a bit more on the performance differences between HashMap and HashTable, as well as mention some common use cases for each class.

Overall, your answer is clear and concise, covering the main differences between HashMap and HashTable. I would rate it 4/5.

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