I have appeared for Java Developer requirement at Wissen Infotech, Bangalore Location. Requirement was for their client Morgan Stanley and it was my second technical round. It was a telephonic interview. Duration : 1 hour

Core Java

1. What is the difference between CountDownLatch and CyclicBarrier.  (Answer)
2. What is the time complexity of put() and get() operation in HashMap? (Answer)
3. Why do we need thredpool in Java Application?  (Answer)
4. What is the time complexity of put() and get() operations in ConcurrentHashMap?
5. How ConcurrentHashMap works internally?
6. If Concurrency level of ConcurrentHashMap is 4, can more than four thread read simultaneously from ConcurrentHashMap?
   Answer  : Yes. Any number of threads can read concurrently from ConcurrentHashMap.
7. If one thread is writing in one segment of ConcurrentHashMap, Can other thread read from that segment?
   Answer : Yes. In that case, reading thread will read last updated value as value field is volatile in ConcurrentHashMap entry object.
8. What is the difference between synchronized keyword and ReentrantLock? Advantages of ReentrantLock over synchronized keyword.

SQL

1. What is the difference between clustered and non-clustered index?

Problem Solving

1. Print 1 to 20 numbers using two different threads concurrently.

Thread 1 prints 1, 3, 5, 7,…,19
Thread 2 prints 2, 4, 6, 8,…,20

2. Find the intersection of two singly linked list? 

For Example, 
    First LinkedList       :  1 -> 2 -> 3 -> 4 -> 5
    Second LinkedList :  10 -> 9 -> 8 -> 7 -> 4 -> 5 

3. I am having website which displays best three prices of the same product from different eCommerce sites.

For Example, 
        Price of Samsung Galaxy S8 is
        64000/- INR on Flipkart
        60000/- INR on Amazon
        66000/- INR on eBay
        63000/- INR on bestBuy
        67000/- INR on Infibeam
        
Our site should display Amazon, bestBuy and Flipkart prices for Samsung Galaxy S8.
Each e-commerce website sends frequent request for any update in price.
    
For processing such request we are having below method signature. 
We need to implement this method such a way that we will ignore such request, if we have already received request in last one hour for the same product from the same e-Commerce site. We need to handle multiple requests concurrently.
    
Explain the logic or the flow of your method?
Which data structure you will use and why?

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