Stellar Informatics Interview Questions and Answers

Hash table and hash map are two names for the same data structure that stores key-value pairs.

• Both use a hash function to map keys to indices in an array

• Hash table is an older term, while hash map is more commonly used in modern programming languages

• Java uses the term HashMap, while Python uses the term dict

• Hash maps/tables have O(1) average case time complexity for insertion, deletion, and retrieval

A collection is a group of objects of the same type while collections are classes that implement data structures.

• Collections are used to store, retrieve, manipulate, and communicate aggregate data.

• Java.util package provides various classes for implementing collections like ArrayList, LinkedList, HashSet, etc.

• Collections can be generic or non-generic, ordered or unordered, and allow duplicates or not.

• Collections can be ...read more

collection is an interface in Java that represents a group of objects while collections is a class that provides utility methods for collections.

• Collection is an interface while Collections is a class

• Collection is a part of Java Collections Framework while Collections is a utility class

• Collection is used to represent a group of objects while Collections is used to provide utility methods for collections

• Example of Colle...read more

Set is an unordered collection of unique elements while vector is an ordered collection of elements.

• Set does not allow duplicates while vector can have duplicates.

• Set is implemented using hash table while vector is implemented using dynamic array.

• Set has faster lookup time while vector has faster iteration time.

• Set is useful when uniqueness is important while vector is useful when order is important.

A program to take user name and print 'Hello, username'

• Create a variable to store the user input

• Use printf or cout to print the greeting with the user input

Database program can be connected using various methods such as JDBC, ODBC, ORM, etc.

• JDBC is a Java API for connecting to databases

• ODBC is a standard API for connecting to databases

• ORM frameworks like Hibernate can be used to connect to databases

• Connection string is used to specify the database connection details