30+ UST Senior Software Engineer Interview Questions and Answers

The task is to find the Nth prime number given a number N.

• A prime number is a number greater than 1 that is not a product of two smaller natural numbers.

• Prime numbers have only two factors - 1 and the number itself.

• Start with a counter at 0 and a number at 2.

• Increment the number by 1 and check if it is prime.

• If it is prime, increment the counter.

• Repeat until the counter reaches N.

• Return the last prime number found.

The question is about designing and implementing a data structure for LRU cache to support get and put operations.

• LRU cache is a cache replacement policy that removes the least recently used item when the cache reaches its capacity.

• The cache is initialized with a capacity and supports get(key) and put(key, value) operations.

• For each get operation, return the value of the key if it exists in the cache, otherwise return -1.

• For each put operation, insert the value in the cache i...read more

Convert Excel column title to corresponding column number.

• Iterate through the characters in the input string from right to left

• Calculate the corresponding value of each character based on its position and multiply by 26^index

• Sum up all the values to get the final column number

Lambda expression in Java is a concise way to represent a single method interface.

• Lambda expressions are used to provide a concise way to implement functional interfaces in Java.

• They can be used to replace anonymous classes when implementing functional interfaces.

• Lambda expressions consist of parameters, an arrow (->), and a body that defines the implementation of the functional interface method.

• Example: (x, y) -> x + y is a lambda expression that takes two parameters and ret...read more

Autowiring in Spring Boot is a way to automatically inject dependencies into Spring beans.

• Autowiring is a feature in Spring that allows the container to automatically inject the dependencies of a bean.

• There are different modes of autowiring in Spring: 'byName', 'byType', 'constructor', 'autodetect', and 'no'.

• For example, in 'byName' autowiring, Spring looks for a bean with the same name as the property being autowired.

The start() method is used to start a new thread and execute the run() method.

• The start() method creates a new thread and calls the run() method.

• The run() method contains the code that will be executed in the new thread.

• Calling the run() method directly will not create a new thread.

• The start() method should be called to start the execution of the new thread.

Thread class is a class in Java that extends the Thread class, while Runnable interface is an interface that implements the run() method.

• Thread class extends the Thread class, while Runnable interface implements the run() method.

• A class can only extend one class, so using Runnable interface allows for more flexibility in inheritance.

• Using Runnable interface separates the task of the thread from the thread itself, promoting better design practices.

Garbage collector in Java is responsible for automatic memory management.

• Garbage collector automatically reclaims memory by freeing objects that are no longer referenced.

• It runs in the background and identifies unused objects based on reachability.

• Different garbage collection algorithms like Mark and Sweep, Copying, and Generational are used.

• Garbage collector can be tuned using JVM options like -Xmx and -Xms.

• Example: System.gc() can be used to suggest garbage collection, but ...read more

The start() method is used to start a new thread, while the run() method contains the code that the thread will execute.

• start() method is used to start a new thread and calls the run() method internally

• run() method contains the code that the thread will execute

• It is recommended to override the run() method with the desired functionality

Exception handling is a mechanism in programming to handle and manage errors or exceptional situations that may occur during program execution.

• Exception handling is used to catch and handle errors or exceptions in a program.

• It allows the program to gracefully handle errors and prevent abrupt termination.

• Exception handling involves the use of try-catch blocks to catch and handle exceptions.

• The catch block contains code to handle the exception, such as displaying an error messa...read more

HashSet is an unordered collection that uses hashing to store elements, while TreeSet is a sorted collection that uses a binary search tree.

• HashSet does not maintain any order of elements, while TreeSet maintains elements in sorted order.

• HashSet allows null values, while TreeSet does not allow null values.

• HashSet has constant time complexity for basic operations like add, remove, and contains, while TreeSet has logarithmic time complexity.

• HashSet is generally faster for addin...read more

Abstract class can have both abstract and non-abstract methods, while interface can only have abstract methods.

• Abstract class can have constructor, fields, and methods, while interface cannot have any implementation.

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

• Abstract classes are used to define common behavior among subclasses, while interfaces are used to define a contract for classes to implement.

• Example: Abstract class 'Animal' with ab...read more

Thread Scheduler is responsible for managing the execution of multiple threads in a multitasking environment.

• Thread Scheduler determines the order in which threads are executed.

• It allocates CPU time to each thread based on priority and scheduling algorithm.

• Time Slicing is a technique used by Thread Scheduler to allocate a fixed time slice to each thread before switching to another.

• It ensures fair execution of threads and prevents a single thread from monopolizing the CPU.

• Exam...read more

Spring Boot offers basic annotations for various functionalities like mapping requests, handling exceptions, defining beans, etc.

• 1. @RestController - Used to define RESTful web services.

• 2. @RequestMapping - Maps HTTP requests to handler methods.

• 3. @Autowired - Injects dependencies automatically.

• 4. @Component - Indicates a class is a Spring component.

• 5. @ExceptionHandler - Handles exceptions in Spring MVC controllers.

The @SpringBootApplication annotation is used to mark the main class of a Spring Boot application.

• It is a combination of @Configuration, @EnableAutoConfiguration, and @ComponentScan annotations.

• It tells Spring Boot to start adding beans based on classpath settings, other beans, and various property settings.

• It is used to bootstrap the Spring application context, starting the auto-configuration, component scanning, and property support.

SOLID principles are a set of five design principles in object-oriented programming to make software designs more understandable, flexible, and maintainable.

• S - Single Responsibility Principle: A class should have only one reason to change.

• O - Open/Closed Principle: Software entities should be open for extension but closed for modification.

• L - Liskov Substitution Principle: Objects of a superclass should be replaceable with objects of its subclasses without affecting the func...read more

Thread starvation occurs when a thread is unable to access the CPU resources it needs to execute its tasks.

• Thread starvation happens when a thread is constantly waiting for a resource that is being monopolized by other threads.

• It can occur due to poor resource management or priority scheduling.

• Examples include a low-priority thread being constantly preempted by high-priority threads or a thread waiting indefinitely for a lock held by another thread.

Abstract class is a class that cannot be instantiated and can have both abstract and non-abstract methods. Interface is a blueprint for a class and can only have abstract methods.

• Abstract class can have constructors while interface cannot.

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

• Abstract class can have instance variables while interface cannot.

• Abstract class can provide default implementations for some methods while interface cannot.

• Int...read more

BlockingQueue is a thread-safe queue that blocks when it is full or empty.

• BlockingQueue is part of the Java Concurrency API.

• It provides methods like put() and take() to add and remove elements from the queue.

• When the queue is full, put() blocks until space becomes available.

• When the queue is empty, take() blocks until an element is available.

• It is commonly used in producer-consumer scenarios.

SDLC and STLC, list vs tuple, assert vs verify

• SDLC (Software Development Life Cycle) is a process followed to develop software

• STLC (Software Testing Life Cycle) is a process followed to test software

• List and tuple are both data structures in Python, but list is mutable while tuple is immutable

• Assert is used to check if a condition is true, while verify is used to check if a web element is present

• Both assert and verify are used in automated testing

• Example: assert 2+2 == 4, ver...read more

RestController is used for RESTful web services while Controller is used for general web requests.

• RestController is a specialization of Controller annotation in Spring framework.

• RestController is used to create RESTful web services that return JSON or XML data.

• Controller is used for handling general web requests and returning views (HTML).

• RestController is typically used for APIs while Controller is used for traditional web applications.

A thread in Java is a lightweight sub-process that allows concurrent execution within a single process.

• Threads allow multiple tasks to be executed concurrently in a Java program

• Threads share the same memory space and resources within a process

• Example: Creating a new thread - Thread myThread = new Thread();

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 collections, arrays, or I/O resources.

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

• Streams are lazy, meaning they only perform operations when necessary.

• Example: List<String> names = Arrays.asList("Alice", "Bob", "Charlie"); Stream<String> stream = names.stream();

Annotations are used to provide metadata about classes, methods, or fields in an API.

• Annotations can be used to provide information about how a method should be handled, such as whether it is deprecated or should be ignored by a compiler.

• Annotations can also be used to provide information about how a class should be serialized or deserialized, such as specifying the format of JSON data.

• Examples of annotations include @Deprecated, @Override, @JsonProperty, and @JsonIgnore.

Use multithreading to print 1 to 100 numbers.

• Create a class that implements Runnable interface

• Override the run() method to print numbers

• Create multiple threads and start them

• Join all threads to ensure all numbers are printed

A URL shortener service that generates short URLs for long links.

• Generate a unique short code for each long URL

• Store the mapping of short code to long URL in a database

• Redirect users from short URL to original long URL

• Consider implementing custom short codes for branding purposes

Spring/Spring Boot is a popular Java framework for building enterprise applications.

• Spring is a lightweight framework for building Java applications

• Spring Boot is an extension of the Spring framework that simplifies the setup and configuration of Spring applications

• Spring provides features like dependency injection, aspect-oriented programming, and more

• Spring Boot includes embedded servers like Tomcat, Jetty, etc. for easy deployment

• Spring Boot also provides auto-configuratio...read more

Procedures do not return a value, while functions return a value.

• Procedures are used to perform a specific task, while functions are used to calculate and return a value.

• Functions can be called from within expressions, while procedures cannot.

• Procedures can have input and output parameters, while functions can only have input parameters.

• Example: Procedure to print a message vs Function to calculate the square root of a number.

STLC (Software Testing Life Cycle) is a systematic process for testing software applications.

• STLC involves planning, designing, executing, and reporting tests.

• Phases of STLC include requirement analysis, test planning, test design, test execution, and test closure.

• Each phase has specific activities and deliverables to ensure thorough testing of the software.

• STLC helps in identifying defects early in the development cycle, reducing costs and improving software quality.

OOPS concepts are fundamental principles in object-oriented programming that help in organizing and designing code.

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

• Inheritance: Allowing a class to inherit properties and behavior from another class.

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

• Abstraction: Hiding the complex implementation details and showing only the necessary features to the user.

Testing framework is a set of guidelines, tools, and processes used to automate and standardize the testing of software applications.

• Testing framework provides a structure for organizing test cases and executing them.

• It includes tools for test automation, such as Selenium for web applications or JUnit for Java.

• Frameworks like TestNG or PyTest offer features like test parameterization, grouping, and reporting.

• Frameworks help in maintaining consistency and efficiency in testing...read more

Selenium is a popular open-source automation testing tool used for web application testing.

• Selenium is used for automating web browsers.

• It supports multiple programming languages like Java, Python, C#, etc.

• Selenium WebDriver is the most commonly used component for writing automation scripts.

• Selenium Grid allows for parallel test execution across different browsers and operating systems.

Indexing in SQL is a technique used to improve the performance of queries by creating indexes on columns in database tables.

• Indexes are created on columns in database tables to speed up data retrieval.

• Indexes can be created using CREATE INDEX statement in SQL.

• Indexes can be unique or non-unique, clustered or non-clustered.

• Examples: CREATE INDEX idx_lastname ON employees(last_name);