Impetus Technologies Java Developer Interview Questions and Answers

Q1. Cycle sort based question
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Q2. Streams api, optional, lambda implementation
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Q3. Hashmap iteration ways
Ans. 
There are multiple ways to iterate over a HashMap in Java.
• Using keySet() and values() methods

• Using entrySet() method

• Using forEach() method with lambda expression
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Q4. Method overriding based code question -> guess the output
Ans. 
Method overriding in Java with code example
• Output will be 'Child class method' as the method in Child class overrides the method in Parent class

• Method overriding is a feature that allows a subclass to provide a specific implementation of a method that is already provided by its superclass

• The method in the subclass should have the same name, return type, and parameters as the method in the superclass
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Q5. Write API to save data
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API to save data in Java
• Use HTTP POST method to send data to the server

• Create a RESTful endpoint to handle the data saving

• Validate the input data before saving it to the database
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20 aptitude,20 comunication,4 program questions

General topics . topics about online class vs office line class

Q1. In this round also they mainly check communication.after that basic questions about the what you put on your resume
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Q1. General round. In this round they told about the company and bond
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Q1. They asked some core Java Concepts,String,Java 8,SpringBoot Architecture,Stream API code
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This test was conducted in MSG browser and it has around 30 questions and around 3 to 5 are related to coding

Our topic of discussion is future of jobs and take the first initiative and don't go off topic and try to agree and add points with the fellow members

Q1. Tell me about yourself
Ans. 
Experienced Java Developer with a passion for creating efficient and scalable solutions.
• Over 5 years of experience in Java development

• Strong knowledge of object-oriented programming principles

• Proficient in Spring framework and Hibernate

• Experience with RESTful web services and microservices architecture

• Familiar with Agile development methodologies
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Q2. Tell me about the project
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Q3. Do you known nodejs
Ans. 
Yes, Node.js is a JavaScript runtime built on Chrome's V8 JavaScript engine.
• Node.js is used for server-side scripting and building scalable network applications.

• It allows developers to use JavaScript for both client-side and server-side development.

• Node.js has a large ecosystem of open-source libraries and frameworks like Express.js.

• It is commonly used for building real-time web applications, APIs, and microservices.
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Q1. Difference between ArrayList and LinkedList?
Ans. 
ArrayList is implemented as a resizable array, while LinkedList is implemented as a doubly linked list.
• ArrayList provides fast random access, LinkedList provides fast insertion and deletion.

• ArrayList uses more memory as it needs to allocate a fixed size array, LinkedList uses more memory for storing references to the next and previous elements.

• Example: ArrayList is better for scenarios where random access is required, ...read more
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Q2. Difference between HashMap and HashTable?
Ans. 
HashMap is non-synchronized and allows null values, while HashTable is synchronized and does not allow null values.
• HashMap is non-synchronized, meaning it is not thread-safe, while HashTable is synchronized and thread-safe.

• HashMap allows null values for both keys and values, while HashTable does not allow null keys or values.

• HashMap is faster than HashTable as it is non-synchronized, but HashTable is preferred in multi...read more
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Q1. What is the contract between hashCode and equals method?
Ans. 
The contract between hashCode and equals method is that if two objects are equal according to the equals method, then their hash codes must also be equal.
• hashCode and equals method must be consistent - if two objects are equal according to equals method, their hash codes must be equal

• If two objects have the same hash code, they may or may not be equal according to equals method

• Overriding equals method in a class requir...read more
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Q2. Features introduced in Java 8
Ans. 
Java 8 introduced several new features including lambda expressions, functional interfaces, streams, and default methods in interfaces.
• Lambda expressions allow you to pass functions as arguments.

• Functional interfaces have a single abstract method and can be used with lambda expressions.

• Streams provide a way to work with sequences of elements.

• Default methods allow interfaces to have method implementations.
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Q3. What are the ways to start a thread
Ans. 
Ways to start a thread in Java
• Extending the Thread class and overriding the run() method

• Implementing the Runnable interface and passing it to a Thread object

• Using a thread pool from the Executors class
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Q4. What will happen if you start a thread which is already running
Ans. 
The thread will continue running as it is already active
• The thread will not be started again if it is already running

• Attempting to start a thread that is already running will not have any effect

• The thread will continue its execution without any interruption
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Q5. Explain about the join and sleep method
Ans. 
Join method is used to wait for a thread to finish its execution, while sleep method is used to pause the execution of a thread for a specified amount of time.
• Join method is used to wait for a thread to finish its execution before moving on to the next task.

• Sleep method is used to pause the execution of a thread for a specified amount of time, allowing other threads to run.

• Example: thread1.join() will wait for thread1 ...read more
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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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