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10+ Jumpfactor Interview Questions and Answers

Updated 5 Feb 2024
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Q1. Smallest Subarray With K Distinct Elements

Given an array A consisting of N integers, your task is to find the smallest subarray of A that contains exactly K distinct integers.

If multiple such subarrays exist,...read more

Ans.

Find the smallest subarray in an array with exactly K distinct elements.

  • Use a sliding window approach to keep track of the subarray with K distinct elements.

  • Use a hashmap to store the frequency of each element in the window.

  • Update the window by expanding or shrinking based on the number of distinct elements.

  • Return the smallest subarray with K distinct elements and the smallest leftmost index.

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Q2. Can you differentiate between ArrayList and Vector in Java?
Ans.

ArrayList is non-synchronized and Vector is synchronized in Java.

  • ArrayList is not synchronized, while Vector is synchronized.

  • ArrayList is faster than Vector.

  • Vector is thread-safe, while ArrayList is not.

  • Example: ArrayList<String> list = new ArrayList<>(); Vector<String> vector = new Vector<>();

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Q3. What is the difference between HashSet and HashMap in Java?
Ans.

HashSet is a collection of unique elements, while HashMap is a key-value pair mapping.

  • HashSet does not allow duplicate elements, HashMap allows duplicate keys but not values.

  • HashSet uses a hash table to store elements, HashMap uses key-value pairs.

  • Example: HashSet<String> set = new HashSet<>(); HashMap<String, Integer> map = new HashMap<>();

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Q4. Can you differentiate between HashMap and Hashtable?
Ans.

HashMap and Hashtable are both data structures in Java used to store key-value pairs, but Hashtable is synchronized while HashMap is not.

  • HashMap allows null values and one null key, while Hashtable does not allow null keys or values.

  • HashMap is not synchronized and is not thread-safe, while Hashtable is synchronized and thread-safe.

  • HashMap is faster than Hashtable for most operations, as it is not synchronized.

  • HashMap is part of the Java Collections Framework, while Hashtable ...read more

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Q5. Can you explain the @RestController annotation in Spring Boot?
Ans.

The @RestController annotation in Spring Boot is used to define a class as a RESTful controller.

  • Used to create RESTful web services in Spring Boot

  • Combines @Controller and @ResponseBody annotations

  • Eliminates the need for @ResponseBody annotation on each method

  • Returns data directly in the response body as JSON or XML

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Q6. Why are Java Strings immutable in nature?
Ans.

Java Strings are immutable to ensure thread safety, security, and optimization.

  • Immutable strings prevent accidental changes, ensuring data integrity.

  • String pooling allows for memory optimization by reusing common strings.

  • Thread safety is guaranteed as strings cannot be modified concurrently.

  • Security is enhanced as sensitive information cannot be altered once set.

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Q7. Write a Java 8 program to iterate through a Stream using the forEach method.
Ans.

Java 8 program to iterate through a Stream using forEach method

  • Create a Stream of elements using Stream.of() or any other method

  • Use the forEach() method to iterate through the Stream and perform an action on each element

  • Example: Stream.of(1, 2, 3, 4, 5).forEach(System.out::println);

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Q8. What are a few features of Spring Boot?
Ans.

Spring Boot is a framework that simplifies the development of Java applications by providing pre-configured setups.

  • Auto-configuration: Spring Boot automatically configures the application based on dependencies added to the project.

  • Embedded server: Spring Boot comes with an embedded Tomcat, Jetty, or Undertow server for easy deployment.

  • Actuator: Provides production-ready features like monitoring, metrics, and health checks for the application.

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Q9. What do you know about the JIT compiler?
Ans.

JIT compiler stands for Just-In-Time compiler, which compiles code during runtime for improved performance.

  • JIT compiler translates bytecode into machine code at runtime

  • It helps in optimizing performance by compiling frequently executed code

  • Examples include Java HotSpot JIT compiler and .NET JIT compiler

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Q10. How does MVC work in Spring?
Ans.

MVC in Spring is a design pattern that separates an application into three main components: Model, View, and Controller.

  • Model represents the data and business logic of the application.

  • View is responsible for rendering the user interface based on the data from the Model.

  • Controller acts as an intermediary between Model and View, handling user input and updating the Model accordingly.

  • Spring MVC provides annotations like @Controller, @RequestMapping, and @ModelAttribute to implem...read more

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Q11. How does Spring Boot work?
Ans.

Spring Boot is a framework that simplifies the development of Java applications by providing pre-configured settings and tools.

  • Spring Boot eliminates the need for manual configuration by providing defaults for most settings.

  • It includes embedded servers like Tomcat, Jetty, or Undertow, making it easy to run applications as standalone JAR files.

  • Spring Boot also offers production-ready features like metrics, health checks, and externalized configuration.

  • It allows developers to q...read more

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Q12. What are Java 8 streams?
Ans.

Java 8 streams are a sequence of elements that support functional-style operations.

  • Streams allow for processing sequences of elements in a functional way.

  • They can be created from various data sources like collections, arrays, or I/O channels.

  • Operations like filter, map, reduce, and collect can be performed on streams.

  • Streams are lazy, meaning intermediate operations are only executed when a terminal operation is called.

  • Example: List<String> names = Arrays.asList("Alice", "Bob...read more

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Q13. What is dependency injection?
Ans.

Dependency injection is a design pattern in which components are given their dependencies rather than creating them internally.

  • Dependency injection helps in achieving loose coupling between classes.

  • It allows for easier testing by providing mock dependencies.

  • There are three types of dependency injection: constructor injection, setter injection, and interface injection.

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