Selenium WebDriver with Java - Basics to Advanced and Frameworks - Difference Between HashMap and HashTable (Interview)

The video tutorial explains the differences between hashmap and hashtable, focusing on synchronization, thread safety, handling of null keys and values, and iteration methods. Hashmap is not synchronized and allows multiple threads to access it simultaneously, while hashtable is synchronized and thread-safe. Hashmap permits null keys and values, unlike hashtable. Iteration in hashmap uses an iterator, whereas hashtable requires an enumerator. These differences are crucial for understanding their use cases in programming.

What is a common interview question regarding HashMap and HashTable?

• How to implement a HashMap?

• What is the difference between HashMap and HashTable?

• What are the uses of HashMap?

• How to optimize a HashTable?

Which of the following is true about HashMap?

• It requires an Enumerator for iteration.

• It is not synchronized and not thread-safe.

• It does not allow null keys.

• It is synchronized and thread-safe.

What happens when multiple threads access a HashMap simultaneously?

• The HashMap locks until one thread finishes.

• The HashMap becomes synchronized.

• The HashMap updates concurrently without synchronization.

• The HashMap throws an exception.

Which data structure allows null keys and values?

• HashMap

• HashTable

• Both HashMap and HashTable

• Neither HashMap nor HashTable

Why might you choose a HashTable over a HashMap?

• To use an Iterator for iteration.

• To allow null keys and values.

• To ensure thread safety and synchronization.

• To improve performance with multiple threads.

Which interface is used to iterate over a HashTable?

• Enumerator

• ListIterator

• Iterator

• Stream

What is a key difference in iterating over HashMap and HashTable?

• HashTable does not support iteration.

• HashMap uses Iterator, HashTable uses Enumerator.

• Both use the same interface for iteration.

• HashMap uses Enumerator, HashTable uses Iterator.