TCS Software Engineer Interview Questions, Process, and Tips

ArrayList is preferred for frequent retrieval operations due to fast random access, while LinkedList is suitable for frequent insertions/deletions.

• Use ArrayList when frequent retrieval operations are required, such as searching for specific elements in a list.

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

• Consider memory overhead and performance trade-offs when decidi...read more

ReentrantLock should be used instead of synchronized when more flexibility and control over locking mechanisms is needed.

• Use ReentrantLock when you need to implement advanced locking mechanisms such as tryLock() or lockInterruptibly().

• ReentrantLock is preferred when you require a fair locking policy to prevent thread starvation.

• Consider using ReentrantLock when you need to handle situations where explicit unlocking is

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 objects based on their values rather than memory addresses

• Override hashCode() method alongside equals() to ensure consistent behavior in collections like HashMap

• Consider implementing Comparable interface for natural ordering of objects

Garbage collection in Java automatically reclaims memory occupied by unused objects using different algorithms and memory regions.

• Java garbage collector automatically reclaims memory from unused objects

• Different types of GC algorithms in JVM: Serial, Parallel, CMS, G1 GC

• Objects managed in Young Generation, Old Generation, PermGen/Metaspace

• Minor GC cleans up short-lived objects in Young Generation

• Major GC (Full GC) recl...read more

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 in a more declarative way.

• Lambda expressions enable the use of functional programming concepts like map, filter,...read more

Checked exceptions must be handled explicitly, while unchecked exceptions do not require explicit handling.

• Use custom exceptions when you want to create your own exception types to handle specific scenarios.

• Custom exceptions can be either checked or unchecked, depending on whether you want to enforce handling or not.

• For example, a custom InvalidInputException can be a checked exception if you want to ensure it is caugh...read more

The Java Memory Model defines how threads interact with shared memory, ensuring visibility and ordering of variable updates in a concurrent environment.

• Volatile ensures changes to a variable are always visible to all threads.

• Synchronized provides mutual exclusion and visibility guarantees.

• Reordering optimizations by the compiler or CPU can lead to unexpected behavior.

• Using thread-safe classes like ConcurrentHashMap avo...read more

Method overloading allows multiple methods with the same name but different parameters, while method overriding allows a subclass to provide a different implementation of a parent method.

• Overloading is used to provide multiple methods with the same name but different parameters within the same class.

• Overriding is used to provide a different implementation of a parent method in a subclass.

• Overloaded methods are resolved...read more

Functional interfaces in Java have exactly one abstract method and work with lambda expressions for concise implementation.

• Functional interfaces have exactly one abstract method, making them suitable for lambda expressions.

• Examples of functional interfaces in Java include Runnable, Callable, Predicate, and Function.

• Default methods in interfaces allow for evolving APIs without breaking backward compatibility.

• Method refe...read more

Java Streams enable functional-style operations on collections with lazy evaluation, unlike Iterators.

• Parallel streams can improve performance by utilizing multiple threads, but may introduce overhead due to thread synchronization.

• Care must be taken to ensure thread safety when using parallel streams in a multi-threaded environment.

• Parallel streams are suitable for operations that can be easily parallelized, such as ma...read more

Immutability in Java refers to objects that cannot be changed after creation, leading to thread safety and prevention of unintended side effects.

• Immutable objects cannot be modified after creation, promoting thread safety and preventing unintended side effects.

• String class in Java is immutable, creating new objects for modifications.

• To create an immutable class, use final fields and avoid setters.

• Collections can be mad...read more

final is for constants, finally for cleanup after try-catch, finalize() for garbage collection. Use try-with-resources for resource management.

• final - declare constants, prevent method overriding, or inheritance

• finally - block after try-catch for cleanup actions

• finalize() - method called by garbage collector before object deletion

• Use try-with-resources for resource management instead of finalize()

Singleton design pattern ensures only one instance of a class exists in the JVM, useful for managing shared resources like database connections.

• Avoid using Singleton when multiple instances of a class are required.

• Avoid Singleton for classes that are not thread-safe.

• Avoid Singleton for classes that need to be easily mockable in unit tests.

Java annotations provide metadata to classes, methods, and fields, improving code readability and maintainability.

• Annotations like @Override, @Deprecated, and @SuppressWarnings provide information about the code to developers and tools.

• Spring framework uses annotations like @Component, @Service, and @Autowired for dependency injection, reducing the need for XML configurations.

• Custom annotations can be created using @in...read more

Java Streams handle parallel processing by dividing data into multiple threads using the ForkJoin framework. Pitfalls include race conditions, order-sensitive operations, and debugging challenges.

• Parallel streams divide data into multiple threads for faster processing

• ForkJoin framework handles parallel execution internally

• Useful for CPU-intensive tasks but may not improve performance for small datasets

• Shared mutable st...read more

ArrayList is preferred for frequent retrieval operations due to fast random access, while LinkedList is suitable for frequent insertions/deletions.

• Use ArrayList when frequent retrieval operations are required, such as searching for elements in a large collection.

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

• Consider memory overhead and performance trade-offs when dec...read more

ReentrantLock should be used instead of synchronized when more flexibility and control over locking mechanisms is needed.

• Use ReentrantLock when you need to implement custom locking strategies or require advanced features like tryLock() and lockInterruptibly().

• ReentrantLock supports fair locking mechanisms, ensuring that threads acquire the lock in the order they requested it.

• Explicit unlocking in ReentrantLock reduces ...read more

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 values of objects instead of their references

• Override hashCode() alongside equals() to ensure proper functioning in collections like HashMap

• Consider implementing Comparable interface for natural ordering in collections

Garbage collection in Java automatically reclaims memory occupied by unused objects using different algorithms and memory regions.

• Java garbage collector automatically reclaims memory from unused objects

• Different types of GC algorithms in JVM: Serial, Parallel, CMS, G1 GC

• Objects managed in Young Generation, Old Generation, and PermGen/Metaspace

• Minor GC cleans up short-lived objects in Young Generation

• Major GC (Full GC) ...read more

Lambda expressions in Java 8 improve readability and maintainability by enabling concise and functional-style programming.

• Lambda expressions allow writing more compact code by reducing boilerplate code.

• They enable passing behavior as arguments to methods, making code more modular and flexible.

• Example: (a, b) -> a + b is a lambda expression that adds two numbers.

Checked exceptions must be handled explicitly, while unchecked exceptions do not require explicit handling.

• Use custom exceptions when you want to create your own exception types to handle specific scenarios.

• Custom exceptions can be either checked or unchecked, depending on whether you want to enforce handling or not.

• For example, a custom InvalidInputException could be a checked exception if you want to ensure it is cau...read more

The Java Memory Model defines how threads interact with shared memory, ensuring visibility and ordering of variable updates in a concurrent environment.

• Volatile keyword ensures changes to a variable are always visible to all threads.

• Synchronized keyword provides mutual exclusion and visibility guarantees.

• Reordering optimizations by the compiler or CPU can lead to unexpected behavior.

• Happens-before relationship determin...read more

Method overloading allows multiple methods with the same name but different parameters, while method overriding allows a subclass to provide a different implementation of a parent method.

• Use method overloading when you want to provide multiple ways to call a method with different parameters.

• Use method overriding when you want to provide a specific implementation of a method in a subclass.

• Example of method overloading: ...read more

Functional interfaces in Java have exactly one abstract method and work with lambda expressions for concise implementation.

• Functional interfaces have exactly one abstract method, such as Runnable, Callable, Predicate, and Function.

• Lambda expressions provide a concise way to implement functional interfaces.

• Default methods in interfaces help in evolving APIs without breaking backward compatibility.

• Method references (::) ...read more

Java Streams enable functional-style operations on collections with lazy evaluation, unlike Iterators.

• Parallel streams can improve performance by utilizing multiple threads, but may introduce overhead due to thread management.

• Care must be taken to ensure thread safety when using parallel streams in a multi-threaded environment.

• Parallel streams are suitable for operations that can be easily parallelized, such as map and...read more

Immutability in Java prevents objects from being changed after creation, promoting thread safety and preventing unintended side effects.

• Immutable objects cannot be modified after creation, promoting thread safety

• String class in Java is immutable, modifications create new objects

• Use final fields and avoid setters to create immutable classes

• Collections can be made immutable using Collections.unmodifiableList()

• Immutabilit...read more

final, finally, and finalize have different meanings in Java. final is for constants, finally for cleanup, and finalize for garbage collection.

• final is used for constants, preventing method overriding, and inheritance

• finally is used for cleanup actions after a try-catch block

• finalize() is called by the garbage collector before object deletion

• Alternatives to finalize() for resource management include using try-with-reso...read more

Singleton design pattern ensures only one instance of a class exists in the JVM, useful for managing shared resources like database connections.

• Avoid using Singleton when multiple instances of a class are required.

• Avoid Singleton for classes that are not thread-safe.

• Avoid Singleton for classes that need to be easily mockable for testing purposes.

Java annotations provide metadata to classes, methods, and fields, improving code readability and maintainability.

• Annotations like @Component, @Service, and @Autowired in Spring help with dependency injection

• Annotations reduce boilerplate code compared to XML configurations

• Custom annotations can be created using @interface

• Reflection APIs allow reading annotation metadata dynamically

• Annotations like @Transactional simpl

Java Streams handle parallel processing by dividing data into multiple threads using the ForkJoin framework. Pitfalls include race conditions, performance issues with small datasets, and debugging challenges.

• Parallel streams divide data into multiple threads for faster processing

• ForkJoin framework handles parallel execution internally

• Useful for CPU-intensive tasks but may not improve performance for small datasets

• Share...read more