Comodo Interview Questions and Answers for Freshers

Q1. Explain Abstraction and Encapsulation
Ans. 
Abstraction focuses on hiding implementation details, while encapsulation bundles data and methods into a single unit.
• Abstraction allows us to focus on the essential features of an object while hiding unnecessary details.

• Encapsulation helps in data hiding by restricting access to certain components of an object.

• Abstraction is achieved through abstract classes and interfaces in Java.

• Encapsulation is implemented using ac...read more
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Q2. Explain the use of Final keyword
Ans. 
Final keyword is used in Java to declare constants, prevent method overriding, and prevent class inheritance.
• Used to declare constants - value cannot be changed once assigned

• Prevents method overriding - method cannot be overridden in child classes

• Prevents class inheritance - class cannot be extended
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Q3. Difference between == operator and equals method
Ans. 
The == operator compares memory addresses, while the equals method compares the actual content of objects.
• The == operator checks if two object references point to the same memory address.

• The equals method checks if two objects have the same content.

• Example: String str1 = new String("hello"); String str2 = new String("hello"); str1 == str2 will return false, but str1.equals(str2) will return true.
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Q4. Explain about Hash Table
Ans. 
Hash table is a data structure that stores key-value pairs and allows for fast retrieval of values based on keys.
• Hash table uses a hash function to map keys to indexes in an array.

• It provides constant time complexity O(1) for insertion, deletion, and retrieval operations.

• Collisions can occur when two keys hash to the same index, which can be resolved using techniques like chaining or open addressing.
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Q5. What is Synchronized keyword
Ans. 
Synchronized keyword is used in Java to control access to shared resources by multiple threads.
• Synchronized keyword is used to create a synchronized block of code, ensuring only one thread can access it at a time.

• It can be applied to methods or code blocks to prevent concurrent access by multiple threads.

• Example: synchronized void myMethod() { // synchronized code block }
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Q6. What is the use of volatile keyword
Ans. 
The volatile keyword in Java is used to indicate that a variable's value will be modified by different threads.
• Ensures visibility of changes to variables across threads

• Prevents compiler optimizations that could reorder code and affect variable values

• Useful for variables accessed by multiple threads without synchronization

• Example: volatile int count = 0;
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Q7. What are checked and unchecked exceptions
Ans. 
Checked exceptions are checked at compile time, while unchecked exceptions are not.
• Checked exceptions must be either caught or declared in the method signature using 'throws' keyword

• Unchecked exceptions do not need to be caught or declared

• Examples of checked exceptions: IOException, SQLException

• Examples of unchecked exceptions: NullPointerException, ArrayIndexOutOfBoundsException
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Q8. Difference between Interface and Abstract class
Ans. 
Interface is a blueprint of a class with only abstract methods, while abstract class can have both abstract and concrete methods.
• Interface cannot have method implementations, while abstract class can have both abstract and concrete methods.

• A class can implement multiple interfaces but can only extend one abstract class.

• Interfaces are used to achieve multiple inheritance in Java, while abstract classes are used to provi...read more
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Q9. Explain Dead lock in multi threading
Ans. 
Deadlock in multithreading occurs when two or more threads are waiting for each other to release resources, resulting in a standstill.
• Deadlock happens when two or more threads are blocked forever, waiting for each other to release resources.

• Four conditions must hold for deadlock to occur: mutual exclusion, hold and wait, no preemption, and circular wait.

• Example: Thread 1 holds resource A and waits for resource B, while...read more
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Q10. How to achieve thread safety in java
Ans. 
Thread safety in Java can be achieved by using synchronization, locks, volatile keyword, and thread-safe data structures.
• Use synchronized keyword to create synchronized blocks or methods

• Use locks from java.util.concurrent.locks package like ReentrantLock

• Use volatile keyword to ensure visibility of changes across threads

• Use thread-safe data structures like ConcurrentHashMap, CopyOnWriteArrayList
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Q11. Difference between PUT and POST method
Ans. 
PUT is used to update or replace an existing resource, while POST is used to create a new resource.
• PUT is idempotent, meaning multiple identical requests will have the same effect as a single request.

• POST is not idempotent, meaning multiple identical requests may have different effects.

• PUT is used to update an existing resource at a specific URI.

• POST is used to create a new resource under a specific URI.

• PUT requests ar...read more
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Q12. What are Spring Actuator
Ans. 
Spring Actuator is a set of production-ready features to help monitor and manage your application.
• Provides endpoints to monitor application health, metrics, and other useful information

• Can be used to check the status of the application, gather metrics, and even perform custom actions

• Helps in troubleshooting and monitoring the application in production environment
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Q13. How to deploy a spring boot application
Ans. 
Spring Boot applications can be deployed using various methods such as embedded servers, Docker containers, and cloud platforms.
• Deploying as a standalone JAR file using embedded servers like Tomcat or Jetty

• Building a Docker image and running the application in a container

• Deploying to cloud platforms like AWS, Azure, or Google Cloud Platform

• Using CI/CD pipelines for automated deployment
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Q14. Write a program with Java 8 to filter the employees based on salary greater than 10,000 from a list of Employee objects.
Ans. 
Program to filter employees with salary > 10,000 using Java 8.
• Use Java 8 Stream API to filter employees based on salary.

• Create a Predicate to check if salary is greater than 10,000.

• Use filter() method to apply the Predicate on the list of Employee objects.
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Q15. How to rollback a transaction in spring boot
Ans. 
To rollback a transaction in Spring Boot, use @Transactional annotation and throw an exception
• Use @Transactional annotation on the method where the transaction needs to be rolled back

• Throw an exception within the method to trigger the rollback process

• Spring will automatically rollback the transaction when an exception is thrown
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Q16. Explain Dependency Injection in spring boot
Ans. 
Dependency Injection is a design pattern in Spring Boot where the dependencies of a class are injected from the outside.
• In Spring Boot, Dependency Injection is achieved through inversion of control, where the control of creating and managing objects is given to the Spring framework.

• Dependencies can be injected into a class using constructor injection, setter injection, or field injection.

• By using Dependency Injection, ...read more
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Q17. Different ways of Dependency Injection
Ans. 
Dependency Injection is a design pattern where the dependencies of an object are provided externally rather than created within the object itself.
• Constructor Injection: Dependencies are provided through the class constructor.

• Setter Injection: Dependencies are set through setter methods.

• Interface Injection: Dependencies are injected through an interface.

• Spring Framework: Uses annotations like @Autowired for Dependency I
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Q18. Explain Security management, how to enable security for APIs.
Ans. 
Security management involves implementing measures to protect APIs from unauthorized access and ensure data integrity.
• Implement authentication mechanisms such as OAuth or API keys to control access to APIs

• Use encryption to secure data transmission between clients and APIs

• Implement rate limiting to prevent abuse and protect against denial of service attacks

• Regularly update and patch API security vulnerabilities to stay ...read more
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Q19. Explain JWT Tokens
Ans. 
JWT Tokens are a type of token used for authentication and authorization in web applications.
• JWT stands for JSON Web Token

• JWT tokens are compact, URL-safe tokens that can be easily transmitted between parties

• JWT tokens consist of three parts: header, payload, and signature

• JWT tokens are often used in stateless authentication systems

• Example: eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJzdWIiOiIxMjM0NTY3ODkwIiwibmFtZSI6IkpvaG...read more
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Q20. How to write a test case for a private method
Ans. 
Use reflection to access and test private methods
• Use reflection to access the private method in the test case

• Set the method accessible using setAccessible(true)

• Invoke the method with the necessary parameters and assert the expected result
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Q21. Stages in Jenkins
Ans. 
Stages in Jenkins are the different steps in a Jenkins pipeline that define the actions to be executed.
• Stages help break down the pipeline into smaller, manageable sections

• Each stage can have multiple steps to be executed

• Stages can be sequential or parallel

• Common stages include build, test, deploy, and notify
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Q22. Write the singleton design pattern
Ans. 
Singleton design pattern ensures a class has only one instance and provides a global point of access to it.
• Create a private static instance of the class.

• Provide a public static method to access the instance.

• Ensure the constructor is private to prevent instantiation from outside the class.
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Q23. What is memory leaks in java
Ans. 
Memory leaks in Java occur when objects are no longer being used but are still held in memory, leading to inefficient memory usage.
• Memory leaks can occur when objects are not properly dereferenced or garbage collected.

• Common causes of memory leaks include circular references, static references, and unclosed resources.

• Examples of memory leaks include not closing database connections or file streams after use.
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Q24. Difference between String and String builder
Ans. 
String is immutable, while StringBuilder is mutable and more efficient for concatenating strings.
• String is immutable, meaning once created, it cannot be changed. StringBuilder is mutable and allows for modifications.

• String concatenation in Java creates a new String object each time, while StringBuilder modifies the existing object.

• StringBuilder is more efficient for concatenating multiple strings as it does not create ...read more
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Q25. Explain Garbage Collection in java
Ans. 
Garbage collection in Java is the process of automatically reclaiming memory that is no longer in use by the program.
• Garbage collection is performed by the JVM to free up memory occupied by objects that are no longer referenced by the program.

• It helps in preventing memory leaks and ensures efficient memory management.

• Java provides automatic garbage collection, so developers do not have to manually free up memory.

• Exampl...read more
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Q26. Difference between Array and ArrayList.
Ans. 
Array is a fixed-size data structure while ArrayList is a dynamic-size data structure in Java.
• Array is a fixed-size collection of elements of the same data type.

• ArrayList is a resizable collection that can store elements of any data type.

• Arrays require a specified size at the time of declaration, while ArrayList can grow dynamically.

• Arrays use square brackets [] for declaration, while ArrayList is a class in Java's col...read more
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Q27. Design patterns used
Ans. 
Various design patterns like Singleton, Factory, Observer, etc. are used to solve common problems in software development.
• Singleton pattern ensures a class has only one instance and provides a global point of access to it.

• Factory pattern creates objects without specifying the exact class of object that will be created.

• Observer pattern defines a one-to-many dependency between objects so that when one object changes stat...read more
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Q28. What is Rest Services
Ans. 
Rest Services are a type of web service that allows communication between different systems over HTTP using standard methods like GET, POST, PUT, DELETE.
• Rest Services are stateless, meaning each request from a client to the server must contain all the information necessary to understand the request.

• They use standard HTTP methods like GET, POST, PUT, DELETE to perform CRUD operations on resources.

• Rest Services typically...read more
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Q1. Two coding questions string manipulation
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Q2. Dp 3d dp question easy one
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Q1. Finance questions - related to option pricing, derivatives, securities such as ABS, CLOs
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Q2. Questions on hedge fund structure, ecosystem, hedge fund strategies
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Q3. Why do you want to join IVP? Why not sell side core finance roles?
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Q1. Math puzzles, Statistics, Probability problems
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Q2. Do you have any technical experience? Data visualization and SQL based
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Q3. Why do you want to join us?
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Q4. What do you know about IVP and the exact nature of work we do?
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Q1. What keeps you going everyday?
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Q2. Why do you want to join IVP and what strengths will make you thrive here?
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They have 4 round total. In first round they take online Aptitide test in college labs.Aptitude topics are (Mcq on C,Java,C++ and quantitative aptitude,logical e.t.c), All rounds are Elimination round.

In 2nd Round they take coding test on your college systems.They don't have their plateform.You have to write code on any offline compiler.Coding question are based on linkedlist,array,string,hashmap only.They give 3 coding question if you solve 2 , you will be selected for next round.
Ques1: given an array of string and their frequency , find the string which have duplicate frequency.
Ques2: Find if an array contain any non empty subarray of zero sum in an array.
Ques 3: Find the string is isomorphic or Not.

Q1. In 3rd Round they ask question form your preferred programming language,Sql queries and basic dsa question like find cycle in linked list.
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Q2. What is Diff between static and final keyword in java
Ans. 
Static keyword is used to create class-level variables and methods, while final keyword is used to make a variable constant.
• Static keyword is used to create variables and methods that belong to the class itself, rather than to any specific instance of the class.

• Final keyword is used to make a variable constant and cannot be changed once it has been assigned a value.

• Static variables are shared among all instances of a c...read more
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Q3. How hashmap internally worked
Ans. 
HashMap internally uses an array of linked lists to store key-value pairs, with keys hashed to determine the index.
• HashMap uses hashing to determine the index of key-value pairs in the array.

• Each index in the array can store multiple key-value pairs in a linked list.

• When a key is inserted, its hash code is used to find the appropriate index in the array.

• If multiple keys hash to the same index, they are stored in a link...read more
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Q4. Find cycle in linkedlist
Ans. 
Detect cycle in a linked list
• Use two pointers approach - slow and fast pointers

• If there is a cycle, the fast pointer will eventually catch up to the slow pointer

• Check if the fast and slow pointers meet at some point to detect the cycle
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Q1. The 4th round is Technical+Hr, They asked question about your tech stack, project and they go deep in the concept so prepare accordingly.
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Q2. What is diff between jvm, jre, jdk
Ans. 
JVM is the Java Virtual Machine that executes Java bytecode. JRE is the Java Runtime Environment that includes JVM and libraries. JDK is the Java Development Kit that includes JRE and development tools.
• JVM is the virtual machine that runs Java bytecode and provides a runtime environment for Java programs.

• JRE includes JVM along with libraries and other components necessary to run Java applications.

• JDK is a development k...read more
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Q3. What is Springboot rest api
Ans. 
Spring Boot is a framework for building Java-based web applications with minimal configuration.
• Spring Boot simplifies the process of creating standalone, production-grade Spring-based applications.

• It provides a range of features like embedded servers, auto-configuration, and production-ready metrics.

• Spring Boot allows developers to quickly set up and run RESTful web services using annotations and minimal XML configurat
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Q4. What is polymorphism and interface , what is difference between interface and abstract class
Ans. 
Polymorphism allows objects of different classes to be treated as objects of a common superclass. Interface is a contract that defines a set of methods that a class must implement.
• Polymorphism allows for flexibility in programming by enabling a single interface to be used to represent multiple types of objects

• Interfaces in Java are similar to abstract classes, but they cannot contain any implementation code

• Abstract cla...read more
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Negative impacts of screen time

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