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MCQs on Java 8 Features | Modern Java Features

300+ Free MCQs Quiz on Core Java | Java Programming MCQs on Java 8 Features | Modern Java Features

MCQs on Java 8 Features

Lambda Expressions

Which of the following is a correct lambda expression syntax?
- a) (int x, int y) -> x + y
- b) (x, y) -> {return x + y;}
- c) (int x, int y) { x + y; }
- d) x, y -> x + y
In Java 8, lambda expressions provide support primarily for which type of programming?
- a) Functional
- b) Procedural
- c) Object-Oriented
- d) Imperative
Which of these statements is true about lambda expressions in Java?
- a) Lambda expressions can only be used in loops.
- b) Lambdas are not compatible with functional interfaces.
- c) Lambda expressions simplify syntax for anonymous functions.
- d) Lambda expressions are used for method overloading.
What is a functional interface in Java 8?
- a) An interface with multiple abstract methods
- b) An interface with a single abstract method
- c) An interface with no methods
- d) An interface with only default methods
Which of the following is a common functional interface in Java 8?
- a) Predicate
- b) Loop
- c) Controller
- d) InterfaceHandler

Streams API

Which statement best describes Java 8’s Streams API?
- a) It processes data in a sequential manner only.
- b) It is used for networking in Java.
- c) It provides a way to process collections of objects in a functional style.
- d) It replaces the file handling package.
Which method would you use to filter elements in a Stream?
- a) map
- b) filter
- c) reduce
- d) forEach
What does the map method do in the Streams API?
- a) Filters elements
- b) Applies a function to each element and returns a new stream
- c) Reduces elements to a single value
- d) Combines streams
In Java Streams, which method is used to convert elements in a stream to a list?
- a) collect(Collectors.toList())
- b) toList()
- c) stream()
- d) filter()
Which method is used to terminate a stream in Java 8?
- a) map
- b) filter
- c) reduce
- d) terminate

Default and Static Methods in Interfaces

Which new method type did Java 8 introduce to interfaces?
- a) Private
- b) Default
- c) Protected
- d) Synchronized
Default methods in interfaces were introduced in Java 8 for which purpose?
- a) To allow interfaces to be backward compatible
- b) To restrict method overriding
- c) To enforce encapsulation
- d) To prevent subclassing
Can default methods be overridden by implementing classes?
- a) Yes
- b) No
- c) Only in abstract classes
- d) Only if marked final
Which keyword is used to define a static method in an interface?
- a) default
- b) final
- c) static
- d) interface
What is a key benefit of static methods in interfaces?
- a) They can be inherited by implementing classes.
- b) They provide utility functions related to the interface.
- c) They enable method overloading in subclasses.
- d) They enforce data encapsulation.

Method References

Which of the following represents a method reference in Java 8?
- a) ClassName::methodName
- b) methodName.ClassName
- c) methodName(ClassName)
- d) ClassName-methodName
Which method reference type refers to an instance method of a particular object?
- a) ClassName::methodName
- b) objectName::methodName
- c) super::methodName
- d) method::objectName
How does System.out::println work in Java 8?
- a) It’s a lambda expression to print text.
- b) It references an instance method for printing.
- c) It’s a method that creates a stream.
- d) It initializes the System class.
Which type of method reference is used to refer to a constructor?
- a) ClassName::new
- b) new ClassName()
- c) ClassName.methodName
- d) ::ClassName
Method references can be seen as shorthand for:
- a) Anonymous inner classes
- b) Complex functions
- c) Constructors only
- d) Enumerations

Lambda Expressions and Streams API Combined

Which statement is true about combining lambda expressions and streams in Java 8?
- a) They are primarily used for creating interfaces.
- b) They allow for functional-style processing of data collections.
- c) They are incompatible with each other.
- d) They can only process numeric data.
What does the following lambda expression with streams do?

javaCopy codeList<String> names = Arrays.asList("Anna", "John", "Emma");
names.stream().filter(name -> name.startsWith("E")).collect(Collectors.toList());

sqlCopy code- a) Collects all names
- b) Collects names starting with "A"
- c) Collects names starting with "E"
- d) Collects only empty names

23. What does Optional in Java 8 help with? – a) Handling null values – b) Replacing arrays – c) Managing exceptions – d) Iterating over collections

Which function would help you avoid null pointer exceptions in streams?
- a) reduce
- b) Optional
- c) map
- d) noneMatch
Which method returns an Optional in Streams API?
- a) filter
- b) findFirst
- c) reduce
- d) map

Additional Questions on Java 8 Features

Java 8 introduced which new package primarily for Date and Time API?
- a) java.time
- b) java.date
- c) java.calendar
- d) java.datetime
Which feature was added to enhance concurrency in Java 8?
- a) java.concurrent
- b) CompletableFuture
- c) ThreadLocal
- d) ConcurrentModification
Which is NOT a core Java 8 feature?
- a) Streams API
- b) Serialization
- c) Lambda Expressions
- d) Default Methods
Collectors.toMap() in Streams API is used to:
- a) Create a list from a stream
- b) Filter elements in a stream
- c) Convert a stream into a map
- d) Sort elements in a stream
What is the role of Collectors.groupingBy()?
- a) Group elements based on a classifier function
- b) Sort stream elements
- c) Split streams into arrays
- d) Create a single-value result

Answer Table

Qno	Answer
1	a) (int x, int y) -> x + y
2	a) Functional
3	c) Lambda expressions simplify syntax for anonymous functions.
4	b) An interface with a single abstract method
5	a) Predicate
6	c) It provides a way to process collections of objects in a functional style.
7	b) filter
8	b) Applies a function to each element and returns a new stream
9	a) collect(Collectors.toList())
10	c) reduce
11	b) Default
12	a) To allow interfaces to be backward compatible
13	a) Yes
14	c) static
15	b) They provide utility functions related to the interface.
16	a) ClassName::methodName
17	b) objectName::methodName
18	b) It references an instance method for printing.
19	a) ClassName::new
20	a) Anonymous inner classes
21	b) They allow for functional-style processing of data collections.
22	c) Collects names starting with “E”
23	a) Handling null values
24	b) Optional
25	b) findFirst
26	a) java.time
27	b) CompletableFuture
28	b) Serialization
29	c) Convert a stream into a map
30	a) Group elements based on a classifier function

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