20+ Interview Questions and Answers

Assigning another value to a string reference creates a new string object in memory.

• Assigning a new value to a string reference creates a new string object in memory

• The original string object remains unchanged

• The new value is stored in a different memory location

• The old value may be garbage collected if there are no other references to it

The finally block will always execute, even if an exception is thrown from the try block.

• The finally block is used to execute code that should always run, regardless of whether an exception is thrown or not.

• If an exception is thrown from the try block, the code in the finally block will still execute.

• This is useful for cleaning up resources, such as closing files or database connections.

• Example: try { // code that may throw an exception } finally { // code that should always ...read more

To get unique values from a collection using stream, use the distinct() method.

• Call the distinct() method on the stream of the collection.

• The distinct() method returns a stream of unique elements.

• Use the collect() method to convert the stream back to a collection.

The '==' operator compares the reference of objects, while the 'equals' method compares the content of objects.

• The '==' operator checks if two objects refer to the same memory location.

• The 'equals' method compares the content of objects based on their implementation.

• The 'equals' method can be overridden to provide custom comparison logic.

• Example: String str1 = new String('hello'); String str2 = new String('hello'); str1 == str2 will be false, but str1.equals(str2) will be tru...read more

Lambda expression is an anonymous function while method reference refers to an existing method

• Lambda expression is used to create an instance of a functional interface

• Method reference is used to refer to an existing method of a class or object

• Lambda expression uses the arrow operator (->) to separate the parameters and the body

• Method reference uses the double colon (::) operator to separate the class or object and the method name

Determines if words in given array are anagram or not using JS

• Create a function that takes an array of strings as input

• Loop through the array and sort each string alphabetically

• Compare the sorted strings to check if they are equal

• Return true if all strings are anagrams, else false

Remove duplicate entries from array of strings using JavaScript

• Use Set to remove duplicates

• Convert Set back to array

• Use spread operator to convert Set to array

JIT compiler stands for Just-In-Time compiler. It dynamically compiles code during runtime for improved performance.

• JIT compiler translates bytecode into machine code at runtime

• It optimizes code execution by identifying frequently executed code and compiling it

• Examples include the JIT compilers used in Java Virtual Machine (JVM) and .NET Common Language Runtime (CLR)

Fail fast and fail safe are two error handling techniques in Java.

• Fail fast approach detects errors as early as possible and stops the program execution immediately.

• Fail safe approach handles errors gracefully and continues program execution.

• Examples of fail fast include NullPointerException and ArrayIndexOutOfBoundsException.

• Examples of fail safe include using try-catch blocks and logging errors instead of throwing exceptions.

AWS tier architecture includes Load Balancer for distributing traffic and S3 for scalable storage.

• AWS tier architecture consists of multiple layers such as presentation, application, and data tiers.

• Load Balancer helps distribute incoming traffic across multiple instances to ensure optimal resource utilization and prevent overload.

• S3 (Simple Storage Service) is a scalable storage solution offered by AWS for storing and retrieving data.

• S3 allows for easy management of data thro...read more

ConcurrentHashMap is a thread-safe implementation of the Map interface in Java.

• It allows multiple threads to access and modify the map concurrently without any external synchronization.

• It achieves this by dividing the map into segments, each of which can be locked independently.

• It provides better performance than synchronized HashMap for concurrent access.

• It is part of the java.util.concurrent package in Java.

• Example: ConcurrentHashMap map = new ConcurrentHashMap<>();

Hashmap and Hashset are data structures used to store key-value pairs and unique values respectively.

• Hashmap uses hashing to store key-value pairs in an array. The hash function is used to map the key to an index in the array.

• Hashset is similar to Hashmap but only stores unique values. It uses hashing to store values in an array.

• Both Hashmap and Hashset have constant time complexity for insertion, deletion, and retrieval operations.

• Hashmap allows null values and one null key,...read more

Migration projects involve moving data, applications, or infrastructure from one system to another.

• Migration of data from on-premises servers to cloud storage

• Upgrading software versions and transferring data to new systems

• Moving applications from one platform to another, such as from Windows to Linux

• Consolidating multiple databases into a single system

Sleep pauses the execution of a thread for a specified time, while wait pauses the execution until a specific condition is met.

• Sleep is a static method of the Thread class, while wait is an instance method of the Object class.

• Sleep is used to introduce a delay in the execution of a thread, while wait is used to wait for a specific condition to be met.

• Sleep releases the lock on the object, while wait does not release the lock.

• Sleep can be interrupted by another thread, while w...read more

Concurrent hashmap allows multiple threads to access and modify the map concurrently.

• Concurrent hashmap is thread-safe and uses internal locking mechanisms to ensure consistency.

• It uses a technique called 'lock striping' to divide the map into multiple segments, each with its own lock.

• This allows multiple threads to access different segments of the map concurrently without blocking each other.

• Concurrent hashmap also uses a technique called 'resizing' to dynamically adjust the...read more

Iterator is a general interface while ListIterator is specific to List interface.

• Iterator can traverse any collection while ListIterator can traverse only List.

• ListIterator can traverse in both directions while Iterator can traverse only forward.

• ListIterator has additional methods like add(), set(), previous(), etc.

• Iterator is used for read-only access while ListIterator is used for both read and write access.

Serialization is the process of converting an object into a stream of bytes to store or transmit it.

• Java provides Serializable interface to enable serialization of objects.

• Serialization can be used for caching, deep cloning, and remote method invocation.

• Deserialization is the process of converting a stream of bytes back into an object.

• Java also provides Externalizable interface for custom serialization.

• Serialization can be controlled using transient and static fields.

I have worked with Azure App Services, Azure Functions, Azure SQL Database, and Azure Blob Storage.

• Azure App Services for hosting web applications

• Azure Functions for serverless computing

• Azure SQL Database for relational database management

• Azure Blob Storage for storing unstructured data

Object-oriented programming paradigm focusing on objects and classes for code organization and reusability.

• Encapsulation: Bundling data and methods that operate on the data into a single unit (class)

• Inheritance: Ability of a class to inherit properties and behavior from another class

• Polymorphism: Ability to present the same interface for different data types