20+ Google Software Engineer Interview Questions and Answers for Freshers

ArrayList is preferred for frequent retrieval operations, while LinkedList is suitable for frequent insertions/deletions.

• Use ArrayList when you need fast random access and retrieval operations, such as searching for elements in a list.

• Choose LinkedList when you need fast insertions/deletions, especially at the beginning or end of the list.

• Consider memory overhead and performance trade-offs when deciding between ArrayList and LinkedList.

• For example, if you have a list of stude...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

• ReentrantLock allows for more fine-grained control over locking and unlocking, reducing the chances of d...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 actual content of objects in user-defined classes.

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

• Implement Comparable interface and override compareTo() for natural ordering of objects.

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

• Force garbage collection in Java using System.gc() or Runtime.getRuntime().gc()

• Not recommended to force garbage collection as it can cause performance issues and disrupt the JVM's optimization

• Example: System.gc();

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 compact syntax for implementing functional interfaces.

• They make code more readable by focusing on the behavior being passed as an argument, rather than the mechanics of how it is implemented.

• Lambda expressions enable developers to write more modular and reusable code, leading to better maintain...read more

Software engineering is the process of designing, developing, testing, and maintaining software.

• It involves using engineering principles to create high-quality software

• It includes various stages such as requirements gathering, design, coding, testing, and maintenance

• Theoretical knowledge includes understanding of algorithms, data structures, programming languages, and software design patterns

• Examples of software engineering practices include Agile, Waterfall, and DevOps metho...read more

ArrayList and LinkedList are both classes in Java that implement the List interface, but they have different underlying data structures.

• ArrayList uses a dynamic array to store elements, providing fast random access but slower insertion and deletion.

• LinkedList uses a doubly linked list to store elements, providing fast insertion and deletion but slower random access.

• Choose ArrayList when you need fast random access and know the size of the list beforehand. Choose LinkedList wh...read more

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 can process elements in a collection in a declarative way, allowing for functional-style operations like map, filter, and reduce.

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

• Iterators are used to iterate over a collection sequentially, while Streams can perform para...read more

Immutability in Java means objects cannot be modified after creation. String class achieves immutability by not allowing changes to its value.

• Immutability means once an object is created, its state cannot be changed.

• String class achieves immutability by making its value final and not providing any methods to modify it.

• Advantages of immutable objects include thread safety, caching, and easier debugging.

• Example: String str = "Hello"; str.concat(" World"); // This does not chang...read more

final, finally, and finalize have different meanings in Java.

• final is a keyword used to declare constants, immutable variables, or prevent method overriding.

• 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.

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.

• Provide a public static method to access the instance.

• Use synchronized keyword or double-checked locking to ensure thread safety.

Method overloading is when multiple methods have the same name but different parameters, while method overriding is when a subclass provides a specific implementation of a method in its superclass.

• Method overloading is achieved within the same class by having multiple methods with the same name but different parameters.

• Method overriding occurs in a subclass that provides a specific implementation of a method that is already provided by its superclass.

• Method overloading is use...read more

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 defining beans, handling transactions, or mapping URLs.

• Built-in annotations in J...read more

Using synchronized keyword for thread synchronization in Java 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 offers more control over locking, ability to try and lock with timeout, ability to create fair locks

• ReentrantLock can be u...read more

The Java garbage collector is responsible for automatically managing memory by reclaiming unused objects.

• The garbage collector in Java runs in the background and automatically reclaims memory from objects that are no longer in use.

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

• Each garbage collection algorithm has its own characteristics and is suitable for different types of applications and workloads.

The Java Memory Model defines how threads interact through memory and how synchronization ensures data consistency.

• Java Memory Model specifies how threads interact with memory, ensuring data consistency

• It defines rules for reading and writing shared variables in a multithreaded environment

• Synchronization mechanisms like synchronized blocks and locks ensure proper visibility and ordering of memory operations

• The 'volatile' keyword in Java ensures that changes made by one thread...read more

Java Streams handle parallel processing by splitting the data into multiple chunks and processing them concurrently.

• Java Streams use the Fork/Join framework to split the data into chunks and process them in parallel.

• Potential pitfalls include increased overhead due to thread management, potential race conditions, and decreased performance for small datasets.

• Pitfalls can be mitigated by ensuring thread safety, avoiding stateful operations, and testing performance with differen...read more

In Java, == compares memory addresses while .equals() compares values of objects. Improper usage can lead to unexpected results.

• Use == to compare primitive data types or check if two objects reference the same memory address.

• Use .equals() to compare the values of objects, such as strings or custom classes.

• Improper usage of == with objects can lead to unexpected results as it compares memory addresses, not values.

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, making code more expressive and efficient.

• Java 8 also introduced default methods in interfaces, allowing for backward compatibility without breaking existing code.

• The new Date and Time...read more

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 abstract method of a functional interface concisely.

• An example of a custom functional interface is 'Calculator' with a single abstract method 'calculate'.

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 ClassNotFoundException, while examples of unchecked exceptions...read more

Spring is a popular Java framework for building web applications and microservices.

• Spring provides a comprehensive programming and configuration model for modern Java-based enterprise applications.

• It offers features like dependency injection, aspect-oriented programming, and transaction management.

• Spring Boot is a popular extension of the framework that simplifies the process of creating standalone, production-grade Spring-based applications.

• Spring is important because it hel...read more