Siemens Senior Systems Engineer Interview Questions, Process, and Tips

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. Find Nth Prime
You are given a number 'N'. Your task is to find Nth prime number.
A prime number is a number greater than 1 that is not a product of two smaller natural numbers. Prime numbers hav...read more
Ans. 
Approach (Using Sieve of Eratosthenes) : 

1) We'll create a global sieve and store values of prime numbers in it and use it to get prime numbers for all queries in constant time.

2) Define global variable MAXSIZE as 10^6+5 and an empty ARRAYOFPRIMES.

3) Initialize boolean array ISPRIME[i] to TRUE for each 2<=i <=MAXSIZE

4) Iterate for each 2 <= p <= MAXSIZE:
4.1) If IsPrime[P] is not changed, then it is a p...read more
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Q2. OOPS Question
Difference between Abstract class and Interface.
Ans. 
The differences between Abstract Class and Interface are as follows : 

Abstract Class:
1) Abstract classes have a default constructor and it is called whenever the concrete subclass is instantiated.

2) It contains Abstract methods as well as Non-Abstract methods.

3) The class which extends the Abstract class shouldn’t require the implementation of all the methods, only Abstract
methods need to be implemented in the con...read more
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Q3. OOPS Question
What is Garbage collector in JAVA?
Ans. 
1) Garbage Collection in Java is a process by which the programs perform memory management automatically.

2) The Garbage Collector(GC) finds the unused objects and deletes them to reclaim the memory. I

3) In Java, dynamic memory allocation of objects is achieved using the new operator that uses some memory and the
memory remains allocated until there are references for the use of the object.

4) When there are no references...read more
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Q4. OOPS Question
What is meant by exception handling?
Ans. 
No one wants its software to fail or crash. Exceptions are the major reason for software failure. The exceptions can be handled in the program beforehand and prevent the execution from stopping. This is known as exception handling.
So exception handling is the mechanism for identifying the undesirable states that the program can reach and specifying the desirable outcomes of such states.
Try-catch is the most common meth
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Q5. Java Question
How ConcurrentHashMap works in Java
Ans. 
According to ConcurrentHashMap Oracle docs,

The constructor of ConcurrentHashMap looks like this :

public ConcurrentHashMap (int initialCapacity, float loadFactor, int concurrencyLevel)

So the above line creates a new, empty map with the specified initial capacity, load factor and concurrency level.
where,
Important Parameters to consider from ConcurrentHashMap Constructor :

initialCapacity - the initial capacity. The implem...read more
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Q6. Java Question
Explain the use of final keyword in variable, method and class.
Ans. 
In Java, the final keyword is used as defining something as constant /final and represents the non-access modifier.

1) final variable :
i) When a variable is declared as final in Java, the value can’t be modified once it has been assigned.

ii) If any value has not been assigned to that variable, then it can be assigned only by the constructor of the class.


2) final method :
i) A method declared as final cannot be overridden...read more
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Q7. Java Question
How would you differentiate between a String, StringBuffer, and a StringBuilder?
Ans. 
1) Storage area : In string, the String pool serves as the storage area. For StringBuilder and StringBuffer, heap
memory is the storage area.

2) Mutability : A String is immutable, whereas both the StringBuilder and StringBuffer are mutable.

3) Efficiency : It is quite slow to work with a String. However, StringBuilder is the fastest in performing operations. The
speed of a StringBuffer is more than a String and less than ...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 Implementation
Design and implement a data structure for Least Recently Used (LRU) cache to support the foll...read more
Ans. 
Structure of an LRU Cache :

1) In practice, LRU cache is a kind of Queue — if an element is reaccessed, it goes to the end of the eviction order.
2) This queue will have a specific capacity as the cache has a limited size. Whenever a new element is brought in, it
is added at the head of the queue. When eviction happens, it happens from the tail of the queue.
3) Hitting data in the cache must be done in constant time, which...read more
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Q2. Multithreading Question
What is the start() and run() method of Thread class?
Ans. 
start(): In simple words, the start() method is used to start or begin the execution of a newly created thread. When the start() method is called, a new thread is created and this newly created thread executes the task that is kept in the run() method. One can call the start() method only once. 

run(): In simple words, the run() method is used to start or begin the execution of the same thread. When the run() metho...read more
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Q3. Multithreading Question
What is BlockingQueue?
Ans. 
BlockingQueue basically represents a queue that is thread-safe. Producer thread inserts resource/element into the queue using put() method unless it gets full and consumer thread takes resources from the queue using take() method until it gets empty. But if a thread tries to dequeue from an empty queue, then a particular thread will be blocked until some other thread inserts an item into the queue, or if a thread tries...read more
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Q4. Multithreading Question
What is thread starvation?
Ans. 
Thread starvation is basically a situation or condition where a thread won’t be able to have regular access to shared resources and therefore is unable to proceed or make progress. This is because other threads have high priority and occupy the resources for too long. This usually happens with low-priority threads that do not get CPU for its execution to carry on.
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Q5. Multithreading Question
What is Thread Scheduler and Time Slicing?
Ans. 
Thread Scheduler: It is a component of JVM that is used to decide which thread will execute next if multiple threads are waiting to get the chance of execution. By looking at the priority assigned to each thread that is READY, the thread scheduler selects the next run to execute. To schedule the threads, it mainly uses two mechanisms: Preemptive Scheduling and Time slicing scheduling. 

Time Slicing: It is especiall...read more
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Q6. OOPS Question
Explain SOLID principles in Object Oriented Design .
Ans. 
The SOLID principle is an acronym of the five principles which is given below :

1) Single Responsibility Principle (SRP)
2) Open/Closed Principle
3) Liskov’s Substitution Principle (LSP)
4) Interface Segregation Principle (ISP)
5) Dependency Inversion Principle (DIP)

Uses of SOLID design principles :

1) The SOLID principle helps in reducing tight coupling.
2) Tight coupling means a group of classes are highly dependent on one ...read more
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Q7. Java Question
What makes a HashSet different from a TreeSet?
Ans. 
Although both HashSet and TreeSet are not synchronized and ensure that duplicates are not present, there are certain properties that distinguish a HashSet from a TreeSet.

1) Implementation: For a HashSet, the hash table is utilized for storing the elements in an unordered manner. However, TreeSet makes use of the red-black tree to store the elements in a sorted manner.

2) Complexity/ Performance: For adding, retrieving, ...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. Basic HR Question
Why should we hire you ?
Ans. 
Tip 1 : The cross questioning can go intense some time, think before you speak.

Tip 2 : Be open minded and answer whatever you are thinking, in these rounds I feel it is important to have opinion.

Tip 3 : Context of questions can be switched, pay attention to the details. It is okay to ask questions in these round,
like what are the projects currently the company is investing, which team you are mentoring. How all is the ...read more
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Q2. Basic HR Question
Why are you looking for a job change?
Ans. 
Tip : For an experienced professional seeking a change, this is a common question. The easiest method to respond
to this question is to state that you are leaving your current work in order to advance your career. Make sure you don't
criticize or speak poorly about the company where you now work.
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