CitiusTech Fullstack Java Application Developer Interview Questions and Answers

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

• HashMap internally uses an array of linked lists to store key-value pairs.

• When a key-value pair is added, the key is hashed to find the index in the array where it will be stored.

• If multiple keys hash to the same index, a linked list is used to handle collisions.

• HashMap allows one null key and multiple null values.

• Th...read more

Singleton class is a class that can only have one instance and provides a global point of access to it.

• Singleton class restricts the instantiation of a class to one object.

• It provides a way to access its unique instance globally.

• Commonly used in scenarios where only one instance of a class is needed, such as database connections or thread pools.

The task is to find all pairs in an array that add up to a given sum.

• Iterate through the array and store each element in a hash set.

• For each element, check if the difference between the sum and the element exists in the hash set.

• If it does, add the pair to the result list.