Infiniminds Junior Java Developer Interview Questions and Answers

Some aptitude test they will conduct

Some coding related java and collections

Q1. Implement a custom stack that allows fetching the minimum element in constant time, O(1).
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Q2. How can one create an immutable class named Employee with fields for name and hobbies defined as List?
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Q3. What changes are required in the Employee class to use it as a key for a HashMap?
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Q4. What is the implementation of the singleton design pattern?
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Q5. Different ways to create a thread
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Q6. What are the SOLID principles in software design, and can you provide examples for each?
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Q1. What is the concept of Object-Oriented Programming (OOP) and can you provide an example?
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Q2. How do threads communicate with each other in Java?
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Q3. Write a program to reverse a linked list.
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Q4. What is the difference between string literals and the string pool?
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Q5. What is the program to print the 90-degree rotated view of a 2D array?
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Q1. Given an array of non-negative integers.Find the length of the longest subsequence such that elements in the subsequence are contiguous integers. The consecutive numbers can be in any order. Example n=7 nu...read more
Ans. 
Find the length of the longest subsequence of contiguous integers in an array.
• Sort the array

• Iterate through the array and check for consecutive integers

• Keep track of the longest subsequence found
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Q2. Get list of pincodes from these objects Employee{ id Long, name String, Addresses : List
} Addresses{ houseNo long, pindcode long, state String, country String, } Ans. Use flatMap to flatten and then use m...read more
Ans. 
Use flatMap and map to extract list of pincodes from Employee objects
• Use flatMap to flatten the list of Addresses in each Employee object

• Use map to iterate over the flattened list and extract the pincodes

• Example: employeeList.stream().flatMap(emp -> emp.getAddresses().stream()).map(address -> address.getPincode()).collect(Collectors.toList())
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Q3. What is Database Pooling, Hikari and its configurations. Java 8 to current enchancements and current java version Factory and Builder design patterns to explain and code Project expalantion and details, Cr...read more
Ans. 
Database pooling is a technique used to manage a pool of database connections for efficient resource utilization. HikariCP is a popular database connection pooling library in Java.
• HikariCP is a high-performance database connection pooling library for Java applications.

• It is known for its low latency and high throughput.

• Configurations for HikariCP include settings such as maximum pool size, connection timeout, and idle ...read more
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It was medium level java coding questions along with springboot, mcqs

Q1. ArrayList vs LinkedList
Ans. 
ArrayList is better for random access and LinkedList is better for frequent insertions and deletions.
• ArrayList uses dynamic array to store elements, allowing fast random access but slower insertions and deletions.

• LinkedList uses doubly linked list to store elements, allowing fast insertions and deletions but slower random access.

• Example: Use ArrayList when you need to frequently access elements by index. Use LinkedList...read more
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Q2. HashMap working
Ans. 
HashMap is a data structure in Java that stores key-value pairs and allows fast retrieval of values based on keys.
• HashMap is part of the Java Collections framework.

• It allows null keys and values.

• HashMap does not maintain insertion order.

• Example: HashMap map = new HashMap<>();
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Q1. Difference between Hashset and Treeset
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Q2. Final Finally and finalize difference
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1 Assignment which you need to solve in front of the interviewer

Q1. Questions on Java Streams
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Q2. Questions on springboot
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Q1. Micro service disadvantage
Ans. 
Microservices can introduce complexity, communication overhead, and potential performance issues.
• Increased complexity due to managing multiple services

• Communication overhead between services

• Potential performance issues due to network latency

• Difficulty in maintaining consistency across services
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Q2. @functionalinterface can we extend or not, map & flatmap
Ans. 
No, @FunctionalInterface cannot be extended. Map and flatMap are default methods in the interface and cannot be overridden.
• No, @FunctionalInterface cannot be extended as it is a single abstract method interface.

• Map and flatMap are default methods in the interface and cannot be overridden.

• Example: public interface MyInterface { void myMethod(); default void myDefaultMethod() { // implementation } }
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