Deloitte Interview Questions, Process, and Tips

String is immutable because its value cannot be changed once it is created.

• Immutable objects are more secure as they cannot be modified by external sources.

• String pool in Java is possible because of immutability.

• StringBuffer and StringBuilder classes are used for mutable strings.

How to make a class immutable in Java?

• Make all fields private and final

• Do not provide any setter methods

• Make the class final

• If mutable fields are present, return a copy of them in getter methods

Hashmap is a data structure that stores key-value pairs and uses hashing to quickly retrieve values.

• Hashmap uses a hash function to map keys to indices in an array.

• Collisions can occur when multiple keys map to the same index, which can be resolved using techniques like chaining or open addressing.

• Retrieving a value from a hashmap is typically an O(1) operation.

• Examples of hashmaps include Python's dictionary and Java'

Hashtable is not thread-safe while Concurrent HashMap is thread-safe.

• Hashtable is a legacy class while Concurrent HashMap is a modern class.

• Concurrent HashMap allows concurrent read and write operations while Hashtable does not.

• Concurrent HashMap uses a technique called lock striping to achieve thread-safety.

• Hashtable is synchronized while Concurrent HashMap is not fully synchronized.

• Concurrent HashMap is faster than H...read more