Java 8 MCQ Questions with Answers

This Java 8 quiz is designed to test your skills with modern Java features. It focuses on practical understanding, output-based questions, and advanced concepts commonly asked in interviews and real-world development.

Practice Java 8 MCQs with Detailed Explanations

Answer at least 12 questions to submit.

Which statement best describes a functional interface in Java 8?

Medium

An interface with exactly one abstract method

An interface with no abstract methods

An interface that can only be implemented by lambdas

An interface with default methods only

What will be the output of the following code? List<Integer> list = Arrays.asList(1, 2, 3); list.stream().map(x -> x * 2).forEach(System.out::print);

Medium

123

246

135

Compilation error

Which Stream operation is considered terminal?

Medium

map()

filter()

peek()

collect()

What is the main purpose of Optional in Java?

Medium

To replace all null values automatically

To avoid NullPointerException by explicit absence handling

To improve performance of method calls

To enforce immutability

Which default method is added to the Iterable interface in Java 8?

Medium

forEach()

stream()

iterator()

spliterator()

What will be the output? Stream.of("a", "bb", "ccc") .filter(s -> s.length() > 1) .count();

Medium

Compilation error

Which functional interface represents a function that takes an argument and returns no result?

Medium

Supplier

Consumer

Predicate

Function

Which method is used to create a Stream from a collection?

Easy

collection.toStream()

collection.stream()

Stream.of(collection)

collection.asStream()

Which Date-Time class in Java 8 is immutable and thread-safe?

Medium

Date

Calendar

LocalDate

SimpleDateFormat

What happens if a stream has no terminal operation?

Medium

It throws an exception

It executes partially

It does not execute at all

It executes eagerly

Which method was added to Map in Java 8?

Medium

putIfAbsent()

add()

append()

insert()

What is the purpose of the @FunctionalInterface annotation?

Medium

It enforces exactly one abstract method

It improves runtime performance

It allows multiple inheritance

It enables lambda caching

Which method short-circuits a stream?

Medium

forEach()

findFirst()

collect()

reduce()

What is the return type of Stream.reduce() without an identity value?

Medium

Object

Optional<T>

Stream<T>

Which Java version introduced the module system?

Medium

Java 8

Java 9

Java 10

Java 11

Practice Java 8 MCQs with Detailed Explanations

Which statement best describes a functional interface in Java 8?

What will be the output of the following code? List<Integer> list = Arrays.asList(1, 2, 3); list.stream().map(x -> x * 2).forEach(System.out::print);

Which Stream operation is considered terminal?

What is the main purpose of Optional in Java?

Which default method is added to the Iterable interface in Java 8?

What will be the output? Stream.of("a", "bb", "ccc") .filter(s -> s.length() > 1) .count();

Which functional interface represents a function that takes an argument and returns no result?

Which method is used to create a Stream from a collection?

Which Date-Time class in Java 8 is immutable and thread-safe?

What happens if a stream has no terminal operation?

Which method was added to Map in Java 8?

What is the purpose of the @FunctionalInterface annotation?

Which method short-circuits a stream?

What is the return type of Stream.reduce() without an identity value?

Which Java version introduced the module system?

Other Objective Questions

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Java 8 Objective Questions and Answers

Practice Java 8 MCQs with Detailed Explanations

Which statement best describes a functional interface in Java 8?

What will be the output of the following code? List<Integer> list = Arrays.asList(1, 2, 3); list.stream().map(x -> x * 2).forEach(System.out::print);

Which Stream operation is considered terminal?

What is the main purpose of Optional in Java?

Which default method is added to the Iterable interface in Java 8?

What will be the output? Stream.of("a", "bb", "ccc") .filter(s -> s.length() > 1) .count();

Which functional interface represents a function that takes an argument and returns no result?

Which method is used to create a Stream from a collection?

Which Date-Time class in Java 8 is immutable and thread-safe?

What happens if a stream has no terminal operation?

Which method was added to Map in Java 8?

What is the purpose of the @FunctionalInterface annotation?

Which method short-circuits a stream?

What is the return type of Stream.reduce() without an identity value?

Which Java version introduced the module system?

Other Objective Questions