TCS Software Engineer Interview Questions, Process, and Tips

Leetcode medium asked. Merging the intervals

Q1. What is spring framework, decorator pattern etc.
Ans. 
Spring framework is a Java platform that provides comprehensive infrastructure support for developing Java applications.
• Spring framework facilitates the development of enterprise applications by providing solutions for dependency injection, aspect-oriented programming, and more.

• It promotes good design practices such as loose coupling and separation of concerns.

• Decorator pattern is a structural design pattern that allow...read more
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Q1. What is indexes
Ans. 
Indexes are data structures used to improve the speed of data retrieval in databases by allowing quick access to specific rows.
• Indexes are created on columns in a database table to speed up the retrieval of rows matching a certain condition.

• They work similar to the index in a book, allowing you to quickly find the information you need.

• Examples of indexes include primary keys, unique keys, and non-unique indexes.
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Q2. What is round robin
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Round robin is a scheduling algorithm that assigns equal time slices to each process in a circular manner.
• Each process is given a small unit of time to execute before moving to the next process

• Helps in achieving fairness in resource allocation

• Used in CPU scheduling, load balancing, and network routing
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Q1. What is the use of volatile keyword?
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Volatile keyword is used in multithreaded programming to indicate that a variable's value can be changed unexpectedly.
• Ensures that the variable is always read from and written to the main memory, not from a cache

• Useful for variables shared between multiple threads to prevent unexpected behavior

• Does not guarantee atomicity or thread safety, additional synchronization may be needed
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Q2. Features of SringBoot
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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 deploy standalone applications.

• Spring Boot offers production-ready features like metrics, health checks, and externali...read more
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Q1. Explain the difference between ArrayList and LinkedList in Java. When would you choose one over the other?
Ans. 
ArrayList and LinkedList are both classes in Java used to store and manipulate collections of data. ArrayList uses an array to store elements, while LinkedList uses a doubly linked list.
• ArrayList is faster for accessing elements by index, while LinkedList is faster for adding or removing elements in the middle of the list.

• ArrayList uses more memory as it needs to allocate space for the entire list upfront, while Linked...read more
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Q2. What are the advantages and disadvantages of using Java’s synchronized keyword for thread synchronization? Can you explain how the ReentrantLock compares to synchronized?
Ans. 
Using Java's synchronized keyword for thread synchronization has advantages like simplicity and disadvantages like potential for deadlock. ReentrantLock offers more flexibility and control.
• Advantages of synchronized keyword: simplicity, built-in support in Java

• Disadvantages of synchronized keyword: potential for deadlock, lack of flexibility

• ReentrantLock advantages: more flexibility, ability to try and lock with timeou...read more
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Q3. What is the difference between == and .equals() in Java? When should each be used, and what issues can arise from improper usage?
Ans. 
In Java, == compares memory addresses while .equals() compares object contents.
• Use == to compare primitive data types and object references.

• Use .equals() to compare object contents, such as strings or custom objects.

• Improper usage can lead to unexpected results, as == may not always work as expected with objects.
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Q4. How does the Java garbage collector work? Can you describe the different types of garbage collection algorithms available in Java?
Ans. 
The Java garbage collector automatically manages memory by reclaiming unused objects.
• The garbage collector in Java runs in the background, periodically checking for objects that are no longer needed.

• There are different types of garbage collection algorithms in Java, such as Serial, Parallel, CMS, G1, and ZGC.

• Each algorithm has its own strengths and weaknesses, and is suited for different types of applications and workl
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Q5. What are the main features of Java 8? Can you explain how lambdas and the Stream API have changed the way Java applications are written?
Ans. 
Java 8 introduced features like lambdas and Stream API which have revolutionized the way Java applications are written.
• Lambdas allow for more concise and readable code by enabling functional programming paradigms.

• Stream API provides a way to process collections of objects in a functional style, allowing for easier parallel processing and improved performance.

• Java 8 also introduced default methods in interfaces, allowin...read more
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Q6. Describe the differences between checked and unchecked exceptions in Java. Provide examples and explain how to handle them properly.
Ans. 
Checked exceptions are checked at compile time, while unchecked exceptions are not. Proper handling involves either catching or declaring the exception.
• Checked exceptions must be either caught or declared in the method signature using the 'throws' keyword.

• Unchecked exceptions do not need to be caught or declared, but can still be handled using try-catch blocks.

• Examples of checked exceptions include IOException and SQLE...read more
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Q7. What is the Java Memory Model, and how does it affect multithreading and synchronization? How does volatile help ensure memory visibility?
Ans. 
The Java Memory Model defines how threads interact through memory and how changes made by one thread are visible to others.
• Java Memory Model ensures that changes made by one thread are visible to other threads.

• It defines the behavior of threads in terms of reading and writing to memory.

• Synchronization in Java ensures that only one thread can access a shared resource at a time.

• Volatile keyword in Java ensures visibility...read more
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Q8. Can you explain the difference between method overloading and method overriding in Java? Provide examples where each should be used.
Ans. 
Method overloading involves creating multiple methods in the same class with the same name but different parameters. Method overriding involves creating a new implementation of a method in a subclass.
• Method overloading is used to provide different implementations of a method based on the number or type of parameters. Example: public void print(int num) and public void print(String str)

• Method overriding is used to provi...read more
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Q9. What are functional interfaces in Java? How do they work with lambda expressions? Provide an example of a custom functional interface.
Ans. 
Functional interfaces in Java are interfaces with a single abstract method. They can be used with lambda expressions for functional programming.
• Functional interfaces have only one abstract method, but can have multiple default or static methods.

• Lambda expressions can be used to implement the single abstract method of a functional interface concisely.

• An example of a custom functional interface is 'Calculator' with a sin
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Q10. What is a Java Stream, and how does it differ from an Iterator? Explain how Streams can be used to process collections efficiently.
Ans. 
Java Stream is a sequence of elements that supports functional-style operations. It differs from Iterator by allowing for more concise and declarative code.
• Streams are designed to allow for functional-style operations on collections, such as map, filter, and reduce.

• Streams do not store elements, they operate on the source data structure (e.g., List) directly.

• Iterators are used to sequentially access elements in a colle...read more
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Q11. Explain the concept of immutability in Java. How does the String class achieve immutability, and what are the advantages of immutable objects?
Ans. 
Immutability in Java means objects cannot be modified after creation. String class achieves immutability by not allowing changes to its value.
• String class in Java is immutable because once a String object is created, its value cannot be changed.

• Any operation that appears to modify a String actually creates a new String object with the modified value.

• Advantages of immutable objects include thread safety, caching, and ea
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Q12. What is the difference between final, finally, and finalize in Java? Provide examples to illustrate their usage.
Ans. 
final, finally, and finalize have different meanings in Java.
• final is a keyword used to declare constants, prevent method overriding, and prevent inheritance.

• finally is a block used in exception handling to execute code after try-catch block.

• finalize is a method used for cleanup operations before an object is garbage collected.
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Q13. Explain the Singleton design pattern in Java. How can you implement it safely to ensure thread safety?
Ans. 
Singleton design pattern ensures a class has only one instance and provides a global point of access to it.
• Create a private static instance of the class.

• Make the constructor private to prevent instantiation from outside the class.

• Provide a public static method to access the instance, creating it if necessary.

• Use synchronized keyword or double-checked locking to ensure thread safety.
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Q14. What are Java annotations, and how are they used in frameworks like Spring? Explain the difference between built-in and custom annotations.
Ans. 
Java annotations are metadata that provide data about a program but do not affect the program itself. They are used in frameworks like Spring to configure and customize behavior.
• Java annotations are used to provide metadata about a program, such as information about classes, methods, or fields.

• In frameworks like Spring, annotations are used to configure various aspects of the application, such as dependency injection, ...read more
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Q15. How do Java Streams handle parallel processing? What are the potential pitfalls of using parallel streams, and how can they be mitigated?
Ans. 
Java Streams can handle parallel processing using parallel streams. Pitfalls include increased complexity and potential for race conditions.
• Java Streams can be processed in parallel by calling the parallel() method on a stream.

• Potential pitfalls of using parallel streams include increased complexity, potential for race conditions, and performance overhead.

• To mitigate these pitfalls, ensure that the operations performed...read more
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Q16. Explain the difference between ArrayList and LinkedList in Java. ArrayList is implemented as a dynamic array, while LinkedList is a doubly linked list. ArrayList provides fast random access (O(1) complexi...read more
Ans. 
ArrayList for frequent retrieval, LinkedList for frequent insertions/deletions.
• Use ArrayList when frequent retrieval operations are needed, such as searching for specific elements in a list.

• Choose LinkedList when frequent insertions/deletions are required, like maintaining a queue or stack.

• Consider memory overhead and performance trade-offs when deciding between ArrayList and LinkedList.
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Q17. What are the advantages and disadvantages of using Java’s synchronized keyword for thread synchronization? The synchronized keyword ensures that only one thread can access a block of code at a time. It pr...read more
Ans. 
ReentrantLock should be used instead of synchronized when more flexibility and control over locking mechanisms are required.
• Use ReentrantLock when you need to implement advanced locking mechanisms like tryLock() or lockInterruptibly().

• ReentrantLock supports fair locking mechanisms, unlike synchronized.

• ReentrantLock allows for explicit unlocking, reducing the chances of human errors.

• Synchronized is simpler and preferred
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Q18. What is the difference between == and .equals() in Java? == checks for reference equality, meaning it compares memory addresses. equals() checks for value equality, which can be overridden in user-defined...read more
Ans. 
In Java, == checks for reference equality while equals() checks for value equality. Misuse of == can lead to logical errors.
• Override equals() when you want to compare the actual content of objects in user-defined classes.

• Override hashCode() alongside equals() to ensure consistent behavior in hash-based collections.

• Consider implementing Comparable interface for natural ordering of objects.
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Q19. How does the Java garbage collector work? Garbage collection in Java automatically reclaims memory occupied by unused objects. The JVM has different types of GC algorithms, including Serial, Parallel, CMS...read more
Ans. 
Garbage collection in Java automatically reclaims memory occupied by unused objects using different GC algorithms.
• Force garbage collection in Java using System.gc() or Runtime.gc() methods.

• Not recommended to force garbage collection as it can cause performance issues by disrupting the JVM's natural memory management.

• Forcing garbage collection can lead to increased CPU usage and potential application slowdowns.
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Q20. What are the main features of Java 8? Java 8 introduced lambda expressions, enabling functional-style programming. The Stream API allows efficient data processing with map, filter, and reduce operations. ...read more
Ans. 
Lambda expressions in Java 8 improve readability and maintainability by allowing concise and functional-style programming.
• Lambda expressions reduce boilerplate code by providing a more concise syntax for implementing functional interfaces.

• They make code more readable by allowing developers to express actions as methods that can be passed around as arguments.

• Lambda expressions enable a more declarative style of programm...read more
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