Morgan Stanley Java Developer Interview Questions and Answers

Q1. Quick sort - keep order same
Ans. 
Quick sort can be modified to maintain the order of equal elements, known as stable quick sort.
• Stable quick sort uses a modified partitioning method to keep equal elements in their original order.

• Example: For array ['apple', 'banana', 'apple', 'orange'], stable sort keeps the first 'apple' before the second.

• Using a stable sorting algorithm like merge sort can also achieve the same result if quick sort isn't stable.
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Q2. Reverse string with spaces but keep the space position intact
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Round 1 was an online hackerank coding test + technical MCQs.

It consisted of 5 MCQs + 1 SQL problem + 1 DSA problem based on queue + 1 Graph question + 1 java based question to create a REST API.

Round duration - 60 minutes
Round difficulty - Easy

Technical Interview round with questions on DSA and Java.

Q1. 
Max Element After Update Operations
Given an array A of size N, initialized with all zeros, and another array ARR of M pairs of integers representing operations. Each operation consists of a range where e...read more
Ans. 
Find the maximum element in an array after performing a series of increment operations on specified ranges.
• Initialize an array of size N with all zeros

• Iterate through the operations and increment elements within specified ranges

• Return the maximum element in the array after all operations
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Q2. Can you explain the internal working of a hash map in Java?
Ans. 
HashMap in Java is a data structure that stores key-value pairs and uses hashing to efficiently retrieve values based on keys.
• HashMap internally uses an array of linked lists to store key-value pairs.

• When a key-value pair is added, the key is hashed to find the index in the array where it will be stored.

• If multiple keys hash to the same index, a linked list is used to handle collisions.

• Retrieving a value involves hashi...read more
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Q3. Why do we need to override the equals and hashCode methods in Java?
Ans. 
Overriding equals and hashCode methods in Java is important for proper object comparison and hashing.
• Equals method is used to compare two objects for equality, while hashCode method is used to generate a unique integer value for an object.

• By overriding equals and hashCode methods, we can ensure that objects are compared based on their actual content rather than memory address.

• This is crucial for collections like HashMa...read more
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Round duration - 60 minutes
Round difficulty - Medium

Technical Interview round with questions based around Java.

Q1. How can you print even and odd numbers in increasing order using two threads in Java?
Ans. 
Use two threads to print even and odd numbers in increasing order.
• Create two threads, one for printing even numbers and one for printing odd numbers.

• Use a shared variable to keep track of the current number to be printed.

• Synchronize access to the shared variable to ensure correct ordering of numbers.

• Use a loop in each thread to print the next number and update the shared variable.
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Q2. What is the internal working of a CopyOnWrite ArrayList?
Ans. 
CopyOnWriteArrayList creates a new copy of the underlying array whenever an element is added, modified, or removed.
• CopyOnWriteArrayList is thread-safe and suitable for scenarios where reads are more frequent than writes.

• Adding, modifying, or removing elements in CopyOnWriteArrayList creates a new copy of the underlying array, ensuring thread safety.

• Iterators on CopyOnWriteArrayList operate on the original array and do ...read more
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Q3. What are the differences between Synchronized Collection and Concurrent Collection in Java?
Ans. 
Synchronized Collection is thread-safe but may have performance issues, while Concurrent Collection is optimized for concurrent access.
• Synchronized Collection uses synchronized keyword to achieve thread-safety, while Concurrent Collection uses non-blocking algorithms like CAS (Compare and Swap).

• Synchronized Collection locks the entire collection during modification, leading to potential performance bottlenecks, while C...read more
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