Core Solutions Inc. Senior Software Engineer Interview Questions and Answers for Experienced

Q1. What is the difference between an abstract class and an interface in object-oriented programming?
Ans. 
Abstract class can have both abstract and non-abstract methods, while interface can only have abstract methods.
• Abstract class can have method implementations, while interface cannot.

• A class can implement multiple interfaces, but can only inherit from one abstract class.

• Interfaces are used to define contracts for classes to implement, while abstract classes are used to provide a common base for subclasses.

• Example: Abstr...read more
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Q2. Abstract classes can have implemented methods; interfaces can only have declarations (before JAVA 8).
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Q1. In trend java questions
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Q1. Advance java questions, questions related to microservice and java 8
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Q1. What is the difference between classes and struct
Ans. 
Classes are reference types while structs are value types.
• Classes support inheritance while structs do not.

• Classes have default access modifier as internal while structs have it as private.

• Classes have a destructor while structs do not.

• Classes are allocated on heap while structs are allocated on stack.

• Classes can be null while structs cannot.
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Q2. Dispatch Queue vs operations
Ans. 
Dispatch Queue is a thread-safe way to execute tasks asynchronously, while Operations are a way to encapsulate tasks.
• Dispatch Queue is a high-level API for managing concurrent operations.

• Operations are objects that encapsulate a single task or multiple tasks.

• Dispatch Queue is simpler to use and recommended for most use cases.

• Operations provide more control over task dependencies and cancellation.

• Both can be used togeth
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It was medium level aptitude . but still many of the students didn't qualify that.
qualify criteria was around 50% marks in aptitude test.
20 questions in 30 minutes

2 coding questions of medium level from leetcode
1. inplace 90 degree matrix rotation
2. longest substring

it was on a paper , not an online mode

General gd round , mainly to check communication

Q1. Oops medium data structure sql questions
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The first round was DSA round and they gave 2 DSA Questions.

Q1. What are oops concepts in java, explain real time scenario
Ans. 
OOPs concepts in Java include inheritance, polymorphism, encapsulation, and abstraction.
• Inheritance allows a subclass to inherit properties and methods from a superclass.

• Polymorphism allows objects to take on multiple forms and behave differently based on their context.

• Encapsulation hides the implementation details of an object and only exposes necessary information.

• Abstraction allows for the creation of abstract class...read more
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Q2. Uses of interface, inheritance
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Interfaces define contracts for behavior, while inheritance allows for code reuse and polymorphism.
• Interfaces allow for loose coupling and abstraction, enabling multiple implementations of the same behavior.

• Inheritance allows for code reuse and extension of existing classes, reducing code duplication.

• Polymorphism allows objects of different classes to be treated as if they were of the same class, simplifying code and i
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Q3. SQL query for join of tables
Ans. 
SQL query for joining tables
• Use JOIN keyword to combine two or more tables based on a related column

• Specify the columns to be selected using SELECT keyword

• Use ON keyword to specify the condition for joining the tables

• Different types of joins include INNER JOIN, LEFT JOIN, RIGHT JOIN, and FULL OUTER JOIN
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Q4. Java concepts used in your project
Ans. 
Used Java concepts such as inheritance, polymorphism, and exception handling in my project.
• Implemented inheritance to create a base class and derived classes with specific functionalities.

• Utilized polymorphism to allow objects of different classes to be treated as if they were of the same class.

• Implemented exception handling to handle errors and prevent program crashes.

• Used interfaces to define a set of methods that a ...read more
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Q5. Overloading vs overriding, practical uses
Ans. 
Overloading is having multiple methods with the same name but different parameters. Overriding is having a method in a subclass with the same name and parameters as a method in the superclass.
• Overloading is used to provide different ways to call a method with different parameters

• Overriding is used to provide a specific implementation of a method in a subclass

• Overloading is resolved at compile-time while overriding is r...read more
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