Test Your Skills: 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.

1.

Medium

Which statement best describes a functional interface in Java 8?

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

2.

Medium

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);

123

246

135

Compilation error

3.

Medium

Which Stream operation is considered terminal?

map()

filter()

peek()

collect()

4.

Medium

What is the main purpose of Optional in Java?

To replace all null values automatically

To avoid NullPointerException by explicit absence handling

To improve performance of method calls

To enforce immutability

5.

Medium

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

forEach()

stream()

iterator()

spliterator()

6.

Medium

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

Compilation error

7.

Medium

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

Supplier

Consumer

Predicate

Function

8.

Easy

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

collection.toStream()

collection.stream()

Stream.of(collection)

collection.asStream()

9.

Medium

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

Date

Calendar

LocalDate

SimpleDateFormat

10.

Medium

What happens if a stream has no terminal operation?

It throws an exception

It executes partially

It does not execute at all

It executes eagerly

11.

Medium

Which method was added to Map in Java 8?

putIfAbsent()

add()

append()

insert()

12.

Medium

What is the purpose of the @FunctionalInterface annotation?

It enforces exactly one abstract method

It improves runtime performance

It allows multiple inheritance

It enables lambda caching

13.

Medium

Which method short-circuits a stream?

forEach()

findFirst()

collect()

reduce()

14.

Medium

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

Object

Optional<T>

Stream<T>

15.

Medium

Which Java version introduced the module system?

Java 8

Java 9

Java 10

Java 11

Practice Java 8 MCQs with Detailed Explanations

1.

Which statement best describes a functional interface in Java 8?

2.

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);

3.

Which Stream operation is considered terminal?

4.

What is the main purpose of Optional in Java?

5.

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

6.

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

7.

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

8.

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

9.

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

10.

What happens if a stream has no terminal operation?

11.

Which method was added to Map in Java 8?

12.

What is the purpose of the @FunctionalInterface annotation?

13.

Which method short-circuits a stream?

14.

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

15.

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

1.

Which statement best describes a functional interface in Java 8?

2.

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);

3.

Which Stream operation is considered terminal?

4.

What is the main purpose of Optional in Java?

5.

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

6.

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

7.

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

8.

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

9.

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

10.

What happens if a stream has no terminal operation?

11.

Which method was added to Map in Java 8?

12.

What is the purpose of the @FunctionalInterface annotation?

13.

Which method short-circuits a stream?

14.

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

15.

Which Java version introduced the module system?

Other Objective Questions