Java MCQs

Naveen AnamaneniUpdated Nov 14, 2026 · 8 min read

easyJava 25java practice mcq quiz revision

Before a board exam, most students do a stack of objective questions: they are quick, they cover a lot of ground, and every wrong answer points straight at a gap. Java placement tests and online assessments work the same way, usually opening with a round of multiple choice questions (MCQs). This page collects MCQs on every major part of core Java, grouped by topic. Each quiz marks your answers and explains every question, so you learn from the mistakes as well as the score.

How to Use These Quizzes

Do one topic at a time, without looking anything up.
Aim for 4 out of 5 or better on each quiz. Below that, reread the lessons for that topic.
For every question you got right by guessing, read the explanation anyway.
Come back a week later and try again. Spaced repetition is what makes it stick.

Java Basics

Object-Oriented Programming

MCQ: OOP

5 questions

1Which OOP principle hides data behind methods?

InheritancePolymorphismEncapsulationAbstraction

2Can a class extend two classes in Java?

YesNoOnly abstract classesOnly with interfaces

3Which is decided at runtime?

Method overloadingMethod overridingStatic method callsConstructor chaining

4What does super() do in a constructor?

Calls a static methodCalls the parent class constructorCreates a new parent objectReturns the parent object

5Which members does an interface allow since Java 9?

Only abstract methodsInstance fieldsAbstract, default, static and private methodsConstructors

Show answers

Encapsulation: Private fields with public methods.
No: A class extends one class but can implement many interfaces.
Method overriding: Overridden methods are chosen by the object's actual type.
Calls the parent class constructor: It must be the constructor's first call to another constructor.
Abstract, default, static and private methods: Fields in interfaces are always public static final constants.

Strings

Exceptions

MCQ: Exceptions

5 questions

1Which is a checked exception?

NullPointerExceptionArithmeticExceptionIOExceptionIllegalArgumentException

2When does a finally block run?

Only if an exception occursOnly if no exception occursAlmost always, whether or not an exception occursNever after return

3What is the parent of all exceptions and errors?

ExceptionErrorThrowableRuntimeException

4What does try-with-resources need from a resource?

It must be SerializableIt must implement AutoCloseableIt must be finalIt must extend Closeable only

5Which keyword declares that a method may throw a checked exception?

throwthrowscatchtry

Show answers

IOException: Checked exceptions extend Exception but not RuntimeException.
Almost always, whether or not an exception occurs: Only System.exit or a JVM crash skips it.
Throwable: Exception and Error both extend Throwable.
It must implement AutoCloseable: close() is called automatically.
throws: throw raises an exception; throws declares one.

Collections

Multithreading

MCQ: Multithreading

5 questions

1Which method starts a new thread?

run()start()init()execute() on Thread

2What does synchronized guarantee?

Faster codeOnly one thread at a time runs the block for that lock, and changes are visibleThreads run in orderNo exceptions

3What does volatile guarantee?

Atomic incrementsVisibility of the latest value across threadsMutual exclusionFaster reads

4Which class gives a thread-safe counter without locks?

IntegerAtomicIntegerThreadLocalStringBuilder

5What do virtual threads (Java 21) make cheap?

CPU-bound loopsLarge numbers of threads that mostly wait for I/OGarbage collectionSynchronization

Show answers

start(): run() just calls the method on the current thread.
Only one thread at a time runs the block for that lock, and changes are visible: Mutual exclusion plus visibility.
Visibility of the latest value across threads: count++ on a volatile field is still not atomic.
AtomicInteger: It uses compare-and-set.
Large numbers of threads that mostly wait for I/O: Blocking a virtual thread frees its carrier thread.

Java 8 and Modern Java

MCQ: Java 8 and modern Java

5 questions

1What is a functional interface?

An interface with only default methodsAn interface with exactly one abstract methodAny interface in java.util.functionAn interface with no methods

2Which stream operation is terminal?

filtermapcollectsorted

3What does Optional.orElse("none") return for an empty Optional?

null"none"An exceptionAn empty string

4Which feature lets you write record Point(int x, int y) {}?

LombokRecords (final in Java 16)EnumsSealed classes

5What does var do?

Makes a variable dynamically typedLets the compiler infer a local variable's static typeDeclares a constantWorks for fields and parameters

Show answers

An interface with exactly one abstract method: A lambda can implement it.
collect: Intermediate operations are lazy until a terminal one runs.
"none": orElse supplies the fallback.
Records (final in Java 16): The compiler generates the rest.
Lets the compiler infer a local variable's static type: The type is still fixed at compile time.

Practice

Easy: Take all seven quizzes in one sitting and record your score for each. Which topic was weakest?
Harder: For your weakest topic, write five new MCQs of your own, each with one correct answer, three believable wrong ones and a one-line explanation. Writing good wrong options is the best way to learn a topic.

Key Takeaways

Was this tutorial helpful?

Lesson 568 of 578

How to Use These Quizzes

Java Basics

Object-Oriented Programming

Strings

Exceptions

Collections

Multithreading

Java 8 and Modern Java

Practice

Key Takeaways

Related tutorials

Array Programs

Core Java Interview Questions

Java Deep Dive Test