Java 8 Quiz - MCQ - Multiple Choice Questions

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Java 8 introduced several new features and enhancements to the programming language. This blog post presents a Java 8 quiz comprising 40+ multiple-choice questions.

This quiz aims to assess your understanding of the new features and concepts introduced in Java 8, such as Java 8 Lambda Expressions, Java 8 Functional Interfaces, Java 8 Method References, and Java 8 Stream API.

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1. What is a lambda expression in Java?

a) A way to define anonymous methods

b) A method with no return type

c) A method that is only available in interfaces

d) A class that implements an interface

Answer:

a) A way to define anonymous methods

Explanation:

Lambda expressions in Java are a way to define anonymous methods (functions) that can be passed as arguments, stored in variables, or returned as values.

2. Which Java version introduced lambda expressions?

a) Java 6

b) Java 7

c) Java 8

d) Java 9

Answer:

c) Java 8

Explanation:

Lambda expressions were introduced in Java 8, bringing functional programming features to the language.

3. What is the Stream API in Java?

a) A feature for handling files in Java

b) A way to process sequences of elements in a functional style

c) A method for sorting arrays

d) An interface for input/output operations

Answer:

b) A way to process sequences of elements in a functional style

Explanation:

The Stream API in Java allows processing sequences of elements in a functional style, enabling operations like filtering, mapping, and reducing.

4. Which method is used to create a stream from a collection in Java?

a) stream()

b) createStream()

c) asStream()

d) toStream()

Answer:

a) stream()

Explanation:

The stream() method is used to create a stream from a collection, such as a List or Set.

5. What does the Optional class in Java represent?

a) A way to represent null values

b) A container that may or may not contain a value

c) A collection of elements

d) A method that returns multiple values

Answer:

b) A container that may or may not contain a value

Explanation:

The Optional class in Java is a container object which may or may not contain a non-null value. It helps in avoiding null pointer exceptions.

6. Which functional interface is commonly used with lambda expressions in Java?

a) Runnable

b) Callable

c) Function

d) Serializable

Answer:

c) Function

Explanation:

The Function interface is a common functional interface used with lambda expressions in Java. It represents a function that takes one argument and returns a result.

7. What is the syntax for a basic lambda expression in Java?

a) (parameters) -> expression

b) (expression) -> parameters

c) {expression} -> parameters

d) (parameters) => expression

Answer:

a) (parameters) -> expression

Explanation:

The basic syntax for a lambda expression in Java is (parameters) -> expression. It can also have a block of code if needed.

8. Can lambda expressions have multiple parameters?

a) Yes, they can have multiple parameters

b) No, they can only have one parameter

c) Yes, but only if they return a value

d) No, they cannot have any parameters

Answer:

a) Yes, they can have multiple parameters

Explanation:

Lambda expressions in Java can have multiple parameters, enclosed in parentheses and separated by commas.

9. What does the Stream API's filter() method do?

a) It filters elements of a stream based on a predicate

b) It maps each element to a collection

c) It reduces elements of a stream

d) It sorts elements in a stream

Answer:

a) It filters elements of a stream based on a predicate

Explanation:

The filter() method in the Stream API is used to filter elements of a stream based on a given predicate.

10. What is the purpose of the forEach() method in the Stream API?

a) To count the elements in the stream

b) To iterate over each element in the stream and perform an action

c) To remove duplicates from the stream

d) To sort the elements in the stream

Answer:

b) To iterate over each element in the stream and perform an action

Explanation:

The forEach() method is a terminal operation that iterates over each element in the stream and performs the specified action.

11. What is a default method in an interface in Java?

a) A method with no implementation

b) A method that must be overridden

c) A method with a default implementation in the interface

d) A method that is called first in a class

Answer:

c) A method with a default implementation in the interface

Explanation:

A default method in an interface is a method with a default implementation. It allows interfaces to evolve without breaking existing implementations.

12. Which method is used to check if a stream is empty?

a) isEmpty()

b) noneMatch()

c) count()

d) allMatch()

Answer:

b) noneMatch()

Explanation:

The noneMatch() method checks if no elements in the stream match a given predicate, which can be used to check if the stream is empty.

13. What is the purpose of the Predicate functional interface in Java?

a) To return an object

b) To perform an action on an object

c) To test a condition on an object

d) To create an object

Answer:

c) To test a condition on an object

Explanation:

The Predicate functional interface in Java is used to test a condition on an object and returns a boolean value.

14. Can lambda expressions be used with the Comparator interface?

a) Yes, lambda expressions can be used with Comparator

b) No, lambda expressions cannot be used with Comparator

c) Yes, but only with Integer objects

d) No, they are only used with Function interface

Answer:

a) Yes, lambda expressions can be used with Comparator

Explanation:

Lambda expressions can be used with the Comparator interface to simplify comparison logic.

15. What is the use of the Optional class in Java?

a) To handle collections of data

b) To represent the presence or absence of a value

c) To throw exceptions

d) To perform arithmetic operations

Answer:

b) To represent the presence or absence of a value

Explanation:

The Optional class in Java is used to represent the presence or absence of a value, helping to avoid null pointer exceptions.

16. Which method is used to retrieve a value from an Optional if it is present?

a) getValue()

b) retrieve()

c) get()

d) fetch()

Answer:

c) get()

Explanation:

The get() method is used to retrieve a value from an Optional if it is present.

17. What is the difference between map() and flatMap() in the Stream API?

a) map() transforms elements, flatMap() flattens nested structures

b) map() filters elements, flatMap() maps them

c) map() reduces elements, flatMap() sorts them

d) There is no difference between map() and flatMap()

Answer:

a) map() transforms elements, flatMap() flattens nested structures

Explanation:

The map() method transforms elements in a stream, while flatMap() flattens nested structures such as streams of streams into a single stream.

18. Can streams be parallelized in Java?

a) Yes, using the parallelStream() method

b) No, streams cannot be parallelized

c) Yes, but only for numeric streams

d) No, only arrays can be parallelized

Answer:

a) Yes, using the parallelStream() method

Explanation:

Streams can be parallelized in Java using the parallelStream() method, which processes elements concurrently on multiple cores.

19. What is the Collectors class in the Stream API used for?

a) To collect elements from a stream into a collection

b) To map elements in a stream

c) To filter elements in a stream

d) To sort elements in a stream

Answer:

a) To collect elements from a stream into a collection

Explanation:

The Collectors class in the Stream API is used to collect elements from a stream into a collection, such as a List or Set.

20. Which method in the Optional class is used to return a default value if the value is absent?

a) orElse()

b) ifPresent()

c) getOrDefault()

d) fetch()

Answer:

a) orElse()

Explanation:

The orElse() method in the Optional class returns a default value if the value is absent.

21. Which new date and time API was introduced in Java 8?

a) java.util.Date

b) java.sql.Date

c) java.time

d) java.date

Answer:

c) java.time

Explanation:

The java.time package introduced in Java 8 provides a new date and time API that is more comprehensive and user-friendly compared to the older java.util.Date and java.sql.Date classes.

22. What does the map() method do in the Stream API?

a) It transforms each element in the stream

b) It maps elements to a new collection

c) It reduces elements to a single value

d) It filters elements in the stream

Answer:

a) It transforms each element in the stream

Explanation:

The map() method in the Stream API transforms each element in the stream using a given function, producing a new stream of transformed elements.

23. Which method is used to check if all elements in a stream match a given predicate?

a) allMatch()

b) anyMatch()

c) noneMatch()

d) matchesAll()

Answer:

a) allMatch()

Explanation:

The allMatch() method is used to check if all elements in a stream match the given predicate.

24. Can streams in Java be reused?

a) Yes, streams can be reused multiple times

b) No, streams cannot be reused once they are consumed

c) Yes, but only parallel streams

d) Yes, if they are collected first

Answer:

b) No, streams cannot be reused once they are consumed

Explanation:

Streams in Java cannot be reused once they are consumed. After a terminal operation is performed, the stream is considered closed and cannot be used again.

25. Which method in the Stream API is used to remove duplicate elements?

a) filter()

b) distinct()

c) unique()

d) removeDuplicates()

Answer:

b) distinct()

Explanation:

The distinct() method in the Stream API is used to remove duplicate elements from a stream, ensuring that each element appears only once.

26. Which method is used to sort elements in a stream?

a) sort()

b) order()

c) sorted()

d) arrange()

Answer:

c) sorted()

Explanation:

The sorted() method in the Stream API is used to sort the elements in a stream either in natural order or using a custom comparator.

27. Which method in the Stream API is used to combine elements of a stream into a single result?

a) map()

b) reduce()

c) combine()

d) collect()

Answer:

b) reduce()

Explanation:

The reduce() method in the Stream API is used to combine elements of a stream into a single result using an accumulator function.

28. What does the findFirst() method do in a stream?

a) It finds the first element in the stream and returns it

b) It finds the first element matching a condition

c) It returns the first element or throws an exception

d) It returns the first non-null element

Answer:

a) It finds the first element in the stream and returns it

Explanation:

The findFirst() method in the Stream API finds the first element in a stream and returns it wrapped in an Optional if it exists.

29. Which method is used to get the count of elements in a stream?

a) size()

b) count()

c) getCount()

d) length()

Answer:

b) count()

Explanation:

The count() method in the Stream API returns the number of elements in the stream.

30. Can you perform parallel processing with the Stream API in Java?

a) Yes, using parallelStream()

b) No, the Stream API does not support parallel processing

c) Yes, but only with List collections

d) No, only arrays support parallel processing

Answer:

a) Yes, using parallelStream()

Explanation:

You can perform parallel processing with the Stream API in Java using the parallelStream() method, which processes elements concurrently on multiple cores.

31. What is the difference between findFirst() and findAny() in the Stream API?

a) findFirst() returns the first element, findAny() returns any element

b) findFirst() is for sequential streams, findAny() is for parallel streams

c) findFirst() returns a non-null element, findAny() returns any element

d) There is no difference

Answer:

a) findFirst() returns the first element, findAny() returns any element

Explanation:

findFirst() returns the first element in a stream, while findAny() returns any element in the stream, potentially more efficient in parallel streams.

32. Which method is used to skip a given number of elements in a stream?

a) drop()

b) skip()

c) omit()

d) jump()

Answer:

b) skip()

Explanation:

The skip() method in the Stream API skips the first n elements and returns a stream containing the remaining elements.

33. Which new interface was introduced in Java 8 to represent a function that takes no arguments and returns a result?

a) Function

b) Supplier

c) Consumer

d) Predicate

Answer:

b) Supplier

Explanation:

The Supplier interface was introduced in Java 8 to represent a function that takes no arguments and returns a result.

34. Can lambda expressions be used with the Runnable interface?

a) Yes, lambda expressions can be used with Runnable

b) No, lambda expressions cannot be used with Runnable

c) Yes, but only for single-threaded applications

d) No, lambda expressions are only used with functional interfaces

Answer:

a) Yes, lambda expressions can be used with Runnable

Explanation:

Lambda expressions can be used with the Runnable interface to simplify the syntax of creating threads or tasks in Java.

35. What is the main purpose of the Stream API in Java?

a) To perform I/O operations

b) To handle exceptions

c) To process collections of data in a functional style

d) To create multi-threaded applications

Answer:

c) To process collections of data in a functional style

Explanation:

The Stream API in Java is designed to process collections of data in a functional style, enabling operations like filtering, mapping, and reducing.

36. What is the purpose of the peek() method in the Stream API?

a) To modify the elements of a stream

b) To view elements of a stream without modifying them

c) To remove elements from a stream

d) To sort the elements of a stream

Answer:

b) To view elements of a stream without modifying them

Explanation:

The peek() method is used to view elements of a stream without modifying them. It is often used for debugging purposes.

37. Which method is used to limit the number of elements in a stream?

a) limit()

b) reduce()

c) cap()

d) filter()

Answer:

a) limit()

Explanation:

The limit() method is used to limit the number of elements in a stream to the specified size.

38. What is the difference between a stream() and a parallelStream() in Java?

a) stream() is faster than parallelStream()

b) parallelStream() processes elements in parallel

c) stream() uses more memory

d) parallelStream() is only for arrays

Answer:

b) parallelStream() processes elements in parallel

Explanation:

The parallelStream() method processes elements in parallel, potentially improving performance on multi-core processors.

39. Which method is used to find the first element in a stream?

a) findFirst()

b) firstElement()

c) getFirst()

d) find()

Answer:

a) findFirst()

Explanation:

The findFirst() method is used to find the first element in a stream and returns an Optional containing the element if it exists.

40. Can lambda expressions be used to create threads in Java?

a) Yes, using the Runnable interface

b) Yes, using the Callable interface

c) No, lambda expressions cannot be used to create threads

d) Yes, using the Supplier interface

Answer:

a) Yes, using the Runnable interface

Explanation:

Lambda expressions can be used to create threads in Java by passing them to the Runnable interface, which is then passed to a Thread.

Conclusion

Congratulations on completing the Java 8 quiz! We hope it challenged your knowledge and provided valuable insights into the new features and concepts introduced in Java 8. Understanding the enhancements in Java 8 is crucial for writing modern and efficient Java code. 

Learn everything about Java 8 features: Java 8 Tutorial and Examples.

Check out 100+ quiz questions: 100+ Quiz Questions to Test Your Java, Spring Boot, Microservices, Hibernate, REST API Skills.

Keep learning, practicing, and embracing the power of Java 8 in your programming journey!

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