Entranscend Consulting Fullstack Java Developer Interview Questions and Answers

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Q1. What is sychronization ?
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Synchronization is the process of coordinating multiple threads to ensure safe and consistent access to shared resources.
• Synchronization is used to prevent race conditions and ensure thread safety.

• It can be achieved using synchronized blocks or methods.

• Synchronization can cause performance issues if not used properly.

• Example: Synchronizing access to a shared counter variable in a multi-threaded application.
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Q2. What is encapsulation ?
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Encapsulation is the process of hiding implementation details and providing access to only necessary information.
• Encapsulation is achieved through access modifiers such as public, private, and protected.

• It helps in achieving data abstraction and information hiding.

• Encapsulation provides better control over the data and prevents unauthorized access.

• Example: A class with private variables and public methods to access the...read more
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Q3. What is interface in java ?
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An interface in Java is a collection of abstract methods and constants that can be implemented by a class.
• Interfaces are used to achieve abstraction and provide a way to implement multiple inheritance in Java.

• All methods in an interface are abstract by default and cannot have a body.

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

• Interfaces can also have default and static methods with a body.

• Ex...read more
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Q4. What is collection framework?
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Collection framework is a set of classes and interfaces that provide a way to store and manipulate groups of objects.
• It provides interfaces like List, Set, Queue, etc. for storing collections of objects.

• It also provides classes like ArrayList, HashSet, PriorityQueue, etc. that implement these interfaces.

• It allows easy manipulation of collections using methods like add, remove, contains, etc.

• It provides algorithms like ...read more
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Q5. What is diffrence between Arraylist and vector ?
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ArrayList is not synchronized while Vector is synchronized.
• ArrayList is faster than Vector as it is not synchronized.

• Vector is thread-safe while ArrayList is not.

• Vector is a legacy class while ArrayList is not.

• Vector can grow by a specified amount while ArrayList grows by 50% of its size.

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

• Example: list.add(1); vector.add(1);

• Example: list.get(0);
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Q6. What are the legacy classes in java?
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Legacy classes in Java are the classes that have been replaced by newer versions but are still supported for backward compatibility.
• Legacy classes are part of the Java API and are still supported for backward compatibility.

• They have been replaced by newer versions but are still used in older applications.

• Examples of legacy classes include Vector, Hashtable, and Enumeration.

• Legacy classes are not recommended for use in ...read more
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Q7. What is joins in SQL ?
Ans. 
Joins in SQL are used to combine data from two or more tables based on a related column.
• Joins are used to retrieve data from multiple tables in a single query.

• There are different types of joins such as inner join, left join, right join, and full outer join.

• Inner join returns only the matching rows from both tables, left join returns all rows from the left table and matching rows from the right table, right join returns...read more
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Q8. What is autoboxing and auto-unboxing ?
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Autoboxing is the automatic conversion of primitive data types to their corresponding object wrapper classes.
• Autoboxing allows primitive data types to be used as objects.

• Auto-unboxing is the reverse process of autoboxing.

• Autoboxing and auto-unboxing are performed automatically by the compiler.

• Example: int i = 10; Integer j = i; // autoboxing

• Example: Integer j = 10; int i = j; // auto-unboxing
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Q9. Difference between where clause and having clause in SQL ?
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Where clause filters rows before grouping, having clause filters groups after grouping.
• Where clause is used to filter rows based on a condition before grouping.

• Having clause is used to filter groups based on a condition after grouping.

• Where clause is used with SELECT, UPDATE, DELETE statements.

• Having clause is used with SELECT statement and GROUP BY clause.

• Where clause cannot contain aggregate functions.

• Having clause c...read more
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Coding is little difficult so please go through logic

Q1. The interview is based on the skills you mentioned in resume
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Q2. What is the use of Java
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Java is a versatile programming language used for developing a wide range of applications, from web and mobile apps to enterprise systems.
• Java is used for developing web applications, mobile applications, desktop applications, and enterprise systems.

• It is commonly used in backend development for server-side programming.

• Java is also used in game development, scientific applications, and big data processing.

• It is platfor...read more
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Q1. Differences between promises and observables
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Promises are used for a single async operation while observables handle multiple async operations and can be cancelled.
• Promises are eager, meaning they start immediately upon creation.

• Observables are lazy, meaning they only start when subscribed to.

• Promises can only handle a single value or error, while observables can handle multiple values over time.

• Observables can be cancelled, while promises cannot be cancelled.

• Pro...read more
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Q2. Angular vs react differences
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Angular and React are both popular front-end frameworks, but they have some key differences in terms of architecture, syntax, and ecosystem.
• Angular is a full-fledged framework with a steep learning curve, while React is a library that is more flexible and easier to learn.

• Angular uses two-way data binding, while React uses one-way data flow.

• Angular has a more opinionated architecture and provides more out-of-the-box fea...read more
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Q1. Java Basic questions
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Q2. SpringBoot Basic questions
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Q3. Simple DSA problem: "introduction" find duplicate characters
Ans. 
Find duplicate characters in a given array of strings
• Iterate through each string in the array

• For each string, iterate through each character and store the count in a hashmap

• If the count of any character is greater than 1, it is a duplicate
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Q4. Write code for REST API using spring boot, include all annotation
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Code for REST API using Spring Boot with annotations
• Use @RestController annotation to define the class as a REST controller

• Use @RequestMapping annotation to map HTTP requests to handler methods

• Use @GetMapping, @PostMapping, @PutMapping, @DeleteMapping annotations for specific HTTP methods

• Use @PathVariable annotation to extract values from the URI

• Use @RequestBody annotation to bind HTTP request body to a method paramete
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Q1. Java 8 code to find occurrence
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Java 8 code to find occurrence of a specific string in an array of strings
• Use Java 8 Stream API to filter the array of strings based on the specific string

• Count the occurrences of the specific string using the 'count' method

• Return the count of occurrences
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Q2. Core java questions
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Q3. Collection questions
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Q4. Spring boot question
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Q1. Basic introduction
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Q2. Salary discussion
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Train and time and work

Q1. Python fullstack
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Q2. Introduction,projects,skills,strenths,habies,goles
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Q3. Python fullstack with django
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Q1. Questions on data types, tuples, generators and iterators.
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Q2. Definitions of above was expected
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