Siemens Senior Systems Engineer Interview Questions and Answers

Round duration - 60 Minutes
Round difficulty - Medium

This round started with 1 coding question related to Prime Numbers in which I was first asked to explain my approach and then write the pseudo code for it. This was followed by some preety standard questions from OOPS and Java.

Q1. 
Nth Prime Number Problem Statement
Find the Nth prime number given a number N.
Explanation:
A prime number is greater than 1 and is not the product of two smaller natural numbers. A prime number has exa...read more
Ans. 
To find the Nth prime number given a number N, implement a function that returns the Nth prime number.
• Create a function that takes N as input and returns the Nth prime number.

• Use a loop to iterate through numbers and check if they are prime.

• Keep track of the count of prime numbers found until reaching N.

• Optimize the algorithm by checking only up to the square root of the number for primality.

• Example: For N = 7, the 7th...read more
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Q2. What is the difference between an abstract class and an interface in OOP?
Ans. 
Abstract class can have both abstract and non-abstract methods, while interface can only have abstract methods.
• Abstract class can have constructors, fields, and methods, while interface cannot.

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

• Abstract classes are used to define a common base class for related classes, while interfaces define a contract for classes to implement.

• Examp...read more
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Q3. What is the garbage collector in Java?
Ans. 
Garbage collector in Java is a built-in mechanism that automatically manages memory by reclaiming unused objects.
• Garbage collector runs in the background to reclaim memory from objects that are no longer in use.

• It helps prevent memory leaks and optimize memory usage.

• Examples of garbage collectors in Java include Serial, Parallel, CMS, and G1.
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Q4. What is meant by exception handling?
Ans. 
Exception handling is a programming concept where errors or exceptional events are dealt with in a structured manner.
• Exception handling allows for graceful handling of errors in a program.

• It involves using try, catch, and finally blocks to manage exceptions.

• Examples include catching divide by zero errors or file not found exceptions.
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Q5. How does ConcurrentHashMap work in Java?
Ans. 
ConcurrentHashMap is a thread-safe implementation of the Map interface in Java.
• ConcurrentHashMap allows multiple threads to read and write to the map concurrently without the need for external synchronization.

• It achieves thread-safety by dividing the map into segments, each of which can be locked independently.

• ConcurrentHashMap uses a combination of synchronized blocks and volatile variables to ensure thread-safety.

• It ...read more
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Round duration - 50 Minutes
Round difficulty - Medium

This round had 1 coding question related to LRU Cache where I had to code its implementation in a production-ready manner explaining my overall approach with proper complexity analysis. This was followed by some Mutithreading questions from Java and then at last the interviewer asked me some basic design patterns in Software Engineering and some more questions related to OOPS.

Q1. 
LRU Cache Design Question
Design a data structure for a Least Recently Used (LRU) cache that supports the following operations:
1. get(key) - Return the value of the key if it exists in the cache; otherw...read more
Ans. 
Design a Least Recently Used (LRU) cache data structure that supports get and put operations with capacity constraint.
• Implement a doubly linked list to keep track of the order of keys based on their recent usage.

• Use a hashmap to store key-value pairs for quick access.

• When capacity is reached, evict the least recently used item before inserting a new item.

• Update the order of keys in the linked list whenever a key is acc...read more
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Q2. What are the start() and run() methods of the Thread class?
Ans. 
The start() method is used to start a new thread, while the run() method contains the code that will be executed by the thread.
• start() method is used to start a new thread and calls the run() method.

• run() method contains the code that will be executed by the thread.

• Calling run() directly will not create a new thread, it will just execute the code in the current thread.
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Q3. What is a BlockingQueue in the context of multithreading?
Ans. 
BlockingQueue is a thread-safe queue that supports operations that wait for the queue to become non-empty when retrieving an element.
• BlockingQueue is part of the java.util.concurrent package in Java.

• It is used to implement producer-consumer scenarios in multithreaded applications.

• Operations like put() and take() are blocking, meaning they will wait until the queue is in a valid state to perform the operation.

• Example: L...read more
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Q4. What is thread starvation?
Ans. 
Thread starvation occurs when a thread is unable to access the CPU resources it needs to execute its tasks.
• Occurs when a thread is constantly preempted by higher priority threads, preventing it from running

• Can lead to performance degradation and delays in task completion

• Can be mitigated by adjusting thread priorities or implementing thread pooling
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Q5. What is a thread scheduler and how does time slicing work?
Ans. 
A thread scheduler is responsible for managing the execution of multiple threads in a system. Time slicing is a technique used by the scheduler to allocate CPU time to each thread.
• Thread scheduler is a component of the operating system that decides which thread to run next

• Time slicing involves dividing the CPU time among multiple threads based on a predefined time interval

• Example: In a round-robin scheduling algorithm,...read more
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Q6. Can you explain the SOLID principles in Object-Oriented Design?
Ans. 
SOLID principles are a set of five design principles in object-oriented programming to make software more maintainable, flexible, and scalable.
• Single Responsibility Principle (SRP) - A class should have only one reason to change.

• Open/Closed Principle (OCP) - Software entities should be open for extension but closed for modification.

• Liskov Substitution Principle (LSP) - Objects of a superclass should be replaceable with...read more
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Q7. What makes a HashSet different from a TreeSet?
Ans. 
HashSet uses a hash table for storage, while TreeSet uses a red-black tree.
• HashSet provides constant-time performance for basic operations like add, remove, contains.

• TreeSet maintains elements in sorted order, allowing for efficient operations like range queries.

• HashSet does not guarantee any specific order of elements, while TreeSet maintains a sorted order.

• Example: HashSet<String> set = new HashSet<>(); T...read more
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Round duration - 30 Minutes
Round difficulty - Easy

This is a cultural fitment testing round .HR was very frank and asked standard questions. Then we discussed about my role.

Q1. Why should we hire you?
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Q2. Why are you looking for a job change?
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