Java Interview Quiz -

Test your Java knowledge with carefully selected interview questions covering Java Basics, OOP, Collections, Multithreading, JVM, Java 8+, Exception Handling, and more.

Welcome to your Java Quiz

Java

join() waits for?

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Lock release

Thread completion

Compilation

Collections

Which collection is thread-safe?

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ArrayList

HashSet

HashMap

Vector

Java Basics

Which class is immutable?

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String

Date

StringBuilder

ArrayList

Java

Callable returns?

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Thread

A value

Nothing

Lock

Java

Serialization marker interface?

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Cloneable

Iterable

Serializable

Closeable

JVM

Which JVM area stores objects?

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PC Register

Heap

Method Area

Stack

Exceptions

Which exception is unchecked?

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IOException

ParseException

NullPointerException

SQLException

Java

ConcurrentHashMap allows?

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No null keys or values with segmented concurrency

Concurrent reads and updates

Only reads

Only one thread

Java

StringBuilder is?

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Immutable

Thread-safe immutable

Synchronized string

Mutable

10.

Java

Function converts?

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T to R

List to Set

Thread to Runnable

R to T

11.

Java

distinct() removes?

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Threads

Exceptions

Duplicate elements

Nulls

12.

Java

CopyOnWriteArrayList is best for?

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Caching

Write-heavy workloads

Sorting

Read-heavy workloads

13.

Java

WeakReference is cleared?

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Immediately

At shutdown

Never

During GC when weakly reachable

14.

Multithreading

Which method starts a thread?

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start()

begin()

run()

execute()

15.

Java

sleep() method belongs to?

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Runnable

Thread

Executor

Object

16.

JVM

Which GC is default in Java17?

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ZGC

CMS

Serial

17.

Java

Future is used to?

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Lock object

Create thread

Serialize

Retrieve async result

18.

Java

Comparable defines?

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Hashing

Natural ordering

Serialization

Custom ordering

19.

Java

ForkJoinPool is designed for?

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Parallel divide-and-conquer tasks

Database access

Networking

Reflection

20.

Collections

Comparable defines?

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Hashing

Natural ordering

Serialization

Custom sort

21.

Algorithms

Bloom filter avoids?

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Disk writes

Unnecessary lookups

Caching

Threads

22.

Java

ThreadLocal stores?

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Static variables

Heap objects

Global values

Per-thread values

23.

Java

Which keyword ensures visibility across threads?

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static

final

transient

volatile

24.

Java

RecursiveAction returns?

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No result

Future

Thread

Integer

25.

Java

happens-before relationship guarantees?

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Serialization

Compilation

Memory visibility

Reflection

26.

Java

transient keyword skips?

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Serialization

Compilation

Reflection

27.

Java 8

Which API processes collections declaratively?

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JDBC

NIO

Reflection

Streams

28.

Java

Which interface supports custom ordering?

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Comparator

Comparable

Cloneable

Iterable

29.

Multithreading

Which keyword creates a thread?

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start

extends

None

new

30.

Java

CountDownLatch is used for?

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Transactions

Waiting for tasks

Caching

Sorting

Java Interview Quiz

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