Juniper Networks Java Developer Interview Questions and Answers

Round duration - 60 minutes
Round difficulty - Easy

Technical Interview round with questions on OOPS and OS mainly.

Q1. What are Little Endian and Big Endian in the context of computer architecture?
Ans. 
Little Endian and Big Endian refer to the order in which bytes are stored in computer memory.
• Little Endian stores the least significant byte first, while Big Endian stores the most significant byte first.

• Little Endian is commonly used in x86 architecture, while Big Endian is used in architectures like SPARC and PowerPC.

• Endianness can affect data transmission between systems with different byte orders.
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Q2. Write a program to determine if your system is little-endian or big-endian.
Ans. 
Program to determine system's endianness
• Check the endianness by storing a multi-byte integer and checking the byte order

• Use bitwise operations to extract the least significant byte

• If the least significant byte is at the lowest memory address, it's little-endian

• If the least significant byte is at the highest memory address, it's big-endian
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Q3. What is the volatile keyword in programming?
Ans. 
The volatile keyword in programming is used to indicate that a variable's value can be changed unexpectedly.
• Volatile keyword is used in multithreaded programming to prevent compiler optimizations on variables that can be changed by other threads.

• It tells the compiler not to cache the variable's value in a register, ensuring that every access is made to the variable's memory location.

• Commonly used in embedded systems pr...read more
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Q4. What is the use of a function pointer in C?
Ans. 
Function pointers in C are used to store the address of functions, allowing for dynamic function calls and callbacks.
• Function pointers can be used to implement callbacks in event-driven programming.

• They can be used to switch between different functions at runtime.

• Function pointers are commonly used in implementing data structures like function pointers in an array of function pointers.

• Example: void (*funcPtr)(int) = &a...read more
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Q5. Design a data structure to implement multi-threading.
Ans. 
Design a data structure for multi-threading
• Use a thread-safe queue to manage tasks for each thread

• Implement a lock or semaphore to control access to shared resources

• Consider using condition variables for synchronization

• Use atomic operations for shared variables to prevent race conditions
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Q6. What does a kernel do?
Ans. 
The kernel is the core component of an operating system that manages system resources and provides a bridge between software and hardware.
• Manages system resources such as CPU, memory, and I/O devices

• Provides a bridge between software applications and hardware components

• Handles tasks such as process scheduling, memory management, and device drivers

• Controls communication between hardware and software layers
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Q7. What is a storage class in programming?
Ans. 
A storage class in programming defines the scope and lifetime of variables.
• Storage classes include auto, register, static, and extern.

• Auto variables are created when a function is called and destroyed when the function ends.

• Register variables are stored in CPU registers for faster access.

• Static variables retain their value between function calls.

• Extern variables are declared outside of any function and can be accessed ...read more
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Round duration - 30 minutes
Round difficulty - Easy

HR round with typical behavioral problems.

Round duration - 70 Minutes
Round difficulty - Medium

This was an Online Coding+MCQ round where we had a total of 50 MCQ questions and 1 coding problem. The coding problem was of easy to medium level but was a bit implementation heavy.

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 maintain the order of recently used keys.

• 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 position of a key in the linked list whenever it is accessed or updated.

• H...read more
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Round duration - 60 Minutes
Round difficulty - Medium

This round had 1 coding question in which I was first required to explain my approach and then discuss the time and space complexities. After this , some basic questions from OOPS and Java were asked.

Q1. 
Detect and Remove Loop in Linked List
For a given singly linked list, identify if a loop exists and remove it, adjusting the linked list in place. Return the modified linked list.
Expected Complexity:
A...read more
Ans. 
Detect and remove loop in a singly linked list in place with O(n) time complexity and O(1) space complexity.
• Use Floyd's Cycle Detection Algorithm to identify the loop in the linked list.

• Once the loop is detected, use two pointers to find the start of the loop.

• Adjust the pointers to remove the loop and return the modified linked list.
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Q2. What is the difference between ArrayList and LinkedList in Java?
Ans. 
ArrayList is implemented using a dynamic array while LinkedList is implemented using a doubly linked list.
• ArrayList provides fast random access but slow insertion and deletion operations.

• LinkedList provides fast insertion and deletion operations but slow random access.

• Example: ArrayList is suitable for scenarios where frequent access and traversal of elements is required, while LinkedList is suitable for scenarios wher...read more
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Q3. What is the difference between abstraction and inheritance?
Ans. 
Abstraction focuses on hiding implementation details, while inheritance allows a class to inherit properties and behavior from another class.
• Abstraction is the concept of hiding the complex implementation details and showing only the necessary features of an object.

• Inheritance is a mechanism where a new class inherits properties and behavior from an existing class.

• Abstraction is achieved through interfaces and abstract...read more
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Round duration - 60 Minutes
Round difficulty - Medium

This round had questions from OS and OOPS. The interviewer also tested my problem solving skills by asking me some puzzles in the end.

Q1. Can you explain piping in Unix/Linux?
Ans. 
Piping in Unix/Linux allows the output of one command to be used as the input for another command.
• Piping is done using the | symbol

• Multiple commands can be piped together

• Piping allows for the creation of complex command chains

• Example: ls -l | grep txt
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Q2. What is a static variable in C?
Ans. 
A static variable in C is a variable that retains its value between function calls.
• Static variables are declared using the 'static' keyword.

• They are initialized only once and retain their value throughout the program's execution.

• Static variables have a default value of 0 if not explicitly initialized.

• They are stored in the data segment of the program's memory.

• Example: static int count = 0; declares a static variable 'c...read more
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Q3. How can you measure exactly 4 liters of water using only a 3-liter can and a 5-liter can?
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Q1. Ispalindrome code in c#
Ans. 
A palindrome code in C# checks if a given string reads the same forwards and backwards.
• Create a function that takes a string as input

• Use a loop to compare characters from the start and end of the string

• Return true if all characters match, false otherwise
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Q1. Check if the linked list is palindrome or not
Ans. 
To check if a linked list is a palindrome, compare the first half of the list with the reversed second half.
• Traverse the linked list to find the middle node

• Reverse the second half of the linked list

• Compare the first half with the reversed second half to check for palindrome
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Q2. C string questions
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Q1. Operating systems questions
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Q2. Linked list and system design question
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Q1. Linked list and double pointers
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