[2] Core Java Quiz

Correct Answers: 0
Incorrect Answers: 0

151. Which of these keywords is used to prevent a class from being subclassed?

abstract

protected

static

final

152. Which method must be implemented by all threads in Java?

notify()

wait()

start()

run()

153. Which collection class allows you to store unique elements but does not guarantee any specific order?

LinkedList

ArrayList

TreeSet

HashSet

154. Which of the following is true about interfaces in Java?

Interfaces can have default methods

Interfaces cannot have constructors

Interfaces support multiple inheritance

All of the above

155. Which of the following packages is automatically imported in every Java program?

java.io

java.lang

java.util

java.math

156. Which of the following cannot be overridden in a subclass?

final method

private method

static method

All of the above

157. Which of the following is not a method of the `String` class?

toUpperCase()

substring()

replace()

reverse()

158. Which of the following is the parent class of all Java classes?

Object

Super

None of the above

Class

159. Which of the following is used to create an instance of a class in Java?

new

construct

class

instanceof

160. Which method in Java is used to get the class of an object?

classType()

class()

getType()

getClass()

161. Which of these is used to define a constant in Java?

constant

static final

final

const

162. Which of the following is a method of the `Thread` class?

run()

stop()

sleep()

All of the above

163. Which of the following is a method for comparing two strings lexicographically in Java?

equals()

compare()

contains()

compareTo()

164. Which of the following is the default value of an instance variable of type `int` in Java?

undefined

null

None

0

165. Which of the following statements about a Java constructor is true?

A constructor cannot have a return type

A constructor must have the same name as the class

A constructor can be overloaded

All of the above

166. Which of the following is the valid declaration of a main method in Java?

public static int main(String args[])

public int main(String args[])

public void main(String args[])

public static void main(String args[])

167. Which of these is used to handle exceptions in Java?

throws

try-catch

throw

None of the above

168. Which of the following is true about the `List` interface in Java?

It allows duplicate elements

It preserves the order of elements

It allows random access

All of the above

169. Which of the following is not a feature of the Java programming language?

Multithreaded

Platform-dependent

Object-oriented

Secure

170. Which data type in Java is used to store true or false values?

int

char

float

boolean

171. Which of the following methods is used to obtain the length of an array in Java?

size()

getLength()

length

length()

172. Which of these is not a valid type of constructor in Java?

Default constructor

Parameterized constructor

Virtual constructor

Copy constructor

173. Which of the following statements is true about constructors in Java?

Constructors cannot be inherited

Constructors can be inherited

Constructors cannot be overloaded

Constructors can have a return type

174. Which of the following keywords is used to implement an interface in Java?

instanceof

import

implements

extends

175. Which of the following will result in a compile-time error in Java?

int arr[] = new int[] {1, 2, 3};

int arr[] = new int(5);

int[] arr = new int[5];

int[] arr = {1, 2, 3};

176. Which of the following is used to compare two objects in Java?

==

Both equals() and compareTo()

compareTo()

equals()

177. Which of the following statements is true about a final variable in Java?

It can be modified after initialization

It can be declared without a value

It must be initialized during declaration

It can only be initialized once

178. Which of the following is true about a static method in Java?

It can access static variables directly

It is always public

It can access non-static variables directly

It can access this or super keyword

179. Which of the following is used to stop the execution of a loop in Java?

break

stop

return

continue

180. Which of the following exceptions is checked at compile time?

ArithmeticException

ArrayIndexOutOfBoundsException

NullPointerException

IOException

181. Which of the following operators is used for bitwise AND in Java?

|

&&

^

&

182. Which of the following is used to invoke a superclass constructor?

this()

super()

superclass()

parent()

183. Which of the following is a feature of the `volatile` keyword in Java?

It ensures thread safety

It prevents variable caching in the CPU

It allows multiple threads to access a variable simultaneously

All of the above

184. Which of these is not a type of inner class in Java?

Anonymous inner class

Synchronized inner class

Static inner class

Local inner class

185. Which of the following classes does not implement the `List` interface in Java?

LinkedList

Vector

HashSet

ArrayList

186. Which method is used to check if a string contains a specific sequence of characters?

contains()

matches()

equals()

substring()

187. Which of the following is not a valid modifier for an interface in Java?

protected

public

abstract

None of the above

188. Which of the following can be used to create an immutable class in Java?

Using final keyword

Not providing setters

Making all fields private

All of the above

189. Which of the following is the size of an `int` data type in Java?

32 bits

64 bits

8 bits

16 bits

190. Which of these is true about a static block in Java?

It executes when the class is loaded

It can initialize static variables

It can have multiple static blocks

All of the above

191. Which method is used to suspend a thread in Java?

sleep()

stop()

wait()

suspend()

192. Which of the following is true about the Java Virtual Machine (JVM)?

It converts Java bytecode to machine code

It provides platform independence

It is part of the JDK

All of the above

193. Which of the following is the default encoding used by Java for Strings?

ASCII

ISO-8859-1

Unicode

UTF-8

194. Which of the following is the correct signature for the `main` method in Java?

public static void main(String args[])

static public void main(String[] args)

public static void main(String[] args)

All of the above

195. Which method is used to start a thread execution in Java?

init()

execute()

start()

run()

196. Which of these classes is used for reading from a file in Java?

FileReader

BufferedReader

BufferedWriter

FileWriter

197. Which of the following is used to create a custom exception in Java?

Inheriting Exception class

Inheriting RuntimeException class

Inheriting Throwable class

All of the above

198. Which of the following is not a wrapper class in Java?

Character

void

Integer

Boolean

199. Which keyword is used to refer to the current object in Java?

super

this

self

object

200. Which of these is true about the `enum` type in Java?

Enums can have constructors

Enums can implement interfaces

Enums can have methods

All of the above

201. Which of the following best describes method overloading in Java?

Two methods with different return types

Two methods with the same name but different parameter lists

Two methods with the same name and same parameters

None of the above

202. Which of the following collections does not allow duplicate elements?

Vector

HashSet

ArrayList

LinkedList

203. Which of the following is not an advantage of Java?

Platform independence

Garbage collection

Low-level programming

Multithreading

204. Which of the following is used to prevent a method from being overridden?

static

abstract

private

final

205. Which of the following is true about anonymous classes in Java?

They are inner classes with no name

They are defined in a method or constructor

They are used to instantiate interfaces or abstract classes

All of the above

206. Which of the following is not a method in the `Object` class?

notify()

wait()

clone()

finalizeAll()

207. Which of these is true about the `finally` block in Java?

It only executes if an exception is thrown

It always executes

It can be skipped under certain conditions

It must come before catch blocks

208. Which of the following is used to convert a primitive data type to an object in Java?

Unboxing

Casting

Autoboxing

Downcasting

209. Which of the following is used to handle exceptions in Java?

if-else statement

switch case

try-catch block

for loop

210. Which keyword is used to create a subclass in Java?

inherits

implements

instanceof

extends

211. Which of the following is the correct way to declare a constant variable in Java?

static int x = 10;

const int x = 10;

int const x = 10;

final int x = 10;

212. Which of the following methods can be used to remove an element from a `List` in Java?

delete()

discard()

remove()

pop()

213. Which of these statements is true about the `HashMap` class?

It is synchronized

It allows null values

It maintains the order of its elements

It allows duplicate keys

214. Which of the following interfaces does `ArrayList` implement?

List

Collection

Iterable

All of the above

215. Which method is called when an object is garbage collected in Java?

delete()

destroy()

dispose()

finalize()

216. Which of the following is a valid declaration of a float variable in Java?

float f = 10.0;

float f = 10;

float f = 10d;

float f = 10.0f;

217. Which of the following is used to declare a method that does not return a value?

empty

void

null

noReturn

218. Which of these collections is synchronized in Java?

HashSet

Vector

HashMap

ArrayList

219. Which of the following statements is true regarding `abstract` classes in Java?

They cannot have constructors

They must contain at least one abstract method

They can be instantiated

They can have abstract methods

220. Which of the following is a method that is automatically called when an object is created?

getter

initializer

finalize

constructor

221. Which of the following operators can be used to concatenate strings in Java?

&

concat()

+

Both + and concat()

222. Which method is used to compare two strings for content equality in Java?

compare()

compareTo()

equals()

==

223. Which of the following is true about the `volatile` keyword in Java?

It prevents the variable from being optimized

It allows multiple threads to access a variable

It ensures the visibility of changes to variables across threads

It makes the variable thread-safe

224. Which of these statements is true about the `Runnable` interface?

It has a single method named run()

It can be implemented by any class

It is used for creating threads

All of the above

225. Which of the following exceptions is thrown when an array is accessed with an illegal index?

ArrayIndexOutOfBoundsException

IllegalArgumentException

NullPointerException

ClassCastException

226. Which of the following is a characteristic of the `TreeSet` class?

It does not allow duplicate elements

It maintains elements in a sorted order

It implements the `Set` interface

All of the above

227. What will happen if you try to compile and run the following code? `int[] arr = new int[5]; arr[5] = 10;`

A syntax error will occur

The value will be added without error

It will compile and run successfully

ArrayIndexOutOfBoundsException will be thrown

228. Which method can be used to create an unmodifiable list in Java?

Collections.unmodifiableList()

List.of()

Both Collections.unmodifiableList() and List.of()

Arrays.asList()

229. Which of the following statements is true about the `super` keyword?

It can be used to refer to the parent class's methods

It can be used to refer to the parent class's constructors

It cannot be used to access private members of the parent class

All of the above

230. Which of the following is a feature of Java?

Object-oriented

Platform-independent

Multithreaded

All of the above

231. Which of the following is used to define an interface in Java?

class

interface

enum

abstract

232. Which of the following is not a valid way to create an array in Java?

int[] arr = {1, 2, 3};

int[] arr = new int[10];

int arr = new int[10];

int arr[] = new int[10];

233. Which of the following is the correct way to define a constant variable?

final int x = 10;

int final x = 10;

const int x = 10;

static final int x = 10;

234. Which of these statements is true regarding constructors in Java?

A constructor can have a return type

A constructor cannot be private

Constructors can be overloaded

All of the above

235. Which of the following statements is true about the `StringBuilder` class?

It is synchronized

It allows modification of strings

It is immutable

It cannot be used to append strings

236. Which of the following is used to get the length of an array in Java?

array.length()

array.size()

array.size

array.length

237. Which of the following exceptions is thrown when a null reference is accessed?

ArrayIndexOutOfBoundsException

ClassCastException

NumberFormatException

NullPointerException

238. Which of the following is true about method overriding in Java?

The method in the subclass must have the same name and parameters as the superclass method

It allows a subclass to provide a specific implementation for a method defined in the superclass

It is a way to achieve runtime polymorphism

All of the above

239. Which of the following keywords is used to prevent method overriding?

static

private

abstract

final

240. Which of the following methods is not present in the `Collection` interface?

clear()

remove()

add()

size()

241. Which of the following methods is used to convert a string to an integer in Java?

Integer.parseInt()

Both Integer.parseInt() and Integer.valueOf()

Integer.valueOf()

String.toInteger()

242. Which of the following data types is not a primitive type in Java?

float

String

int

boolean

243. Which of the following statements is true about the `finalize()` method?

It is called before an object is destroyed

It can be called explicitly by the programmer

It is not guaranteed to be called

All of the above

244. Which of the following is true about the `instanceof` operator?

It checks if an object is an instance of a class or interface

It can only be used with classes

It returns a boolean value

Both A and C

245. Which of the following can be used to implement a stack in Java?

ArrayList

LinkedList

Vector

All of the above

246. What will be the output of the following code? `System.out.println(5 + 5 + '5');`

Error

10

55

15

247. Which of the following statements is true about method overloading?

Both A and C

It is a type of runtime polymorphism

Methods can have the same name but different parameters

It is achieved by defining methods in different classes

248. What is the default value of a reference variable in Java?

0

null

false

undefined

249. Which of the following is used to read input from the user in Java?

Scanner class

InputStream class

BufferedReader class

All of the above

250. Which of the following is not a valid way to define a method in Java?

static void methodName()

public void methodName()

protected methodName()

private int methodName(int a)

251. Which of the following keywords is used to declare an interface in Java?

interface

class

enum

abstract

252. Which of the following is the correct way to handle exceptions in Java?

try-catch-finally

finally-catch-try

catch-try-finally

try-finally-catch

253. Which of the following is true about the `abstract` keyword?

It can be applied to classes and methods

Abstract classes cannot be instantiated

It is used to declare incomplete classes

All of the above

254. Which of the following interfaces is used for handling collections in Java?

Collection

List

Set

All of the above

255. Which of the following is true about the `String` class in Java?

Strings are mutable

Strings are immutable

Strings can be changed after creation

All of the above

256. What will be the output of the following code? `System.out.println(10 / 3);`

3.0

3.33

Error

3

257. What is the purpose of the `main` method in Java?

It is the entry point of any Java application

It is used to define methods

It is used for class constructors

It is used to declare variables

258. Which of the following keywords is used to inherit a class in Java?

inherits

extends

base

implements

259. Which of the following statements is true about Java's garbage collection?

It is done manually by the programmer

It is done automatically by the JVM

It can be forced to run using `System.gc()`

Both B and C

260. Which of the following access modifiers allows visibility only within the same package?

protected

private

public

default

261. Which of the following is the correct syntax to declare a multi-dimensional array in Java?

int[][] arr;

int arr[][];

int[] arr[];

All of the above

262. Which exception is thrown when a division by zero occurs?

NullPointerException

IllegalArgumentException

IndexOutOfBoundsException

ArithmeticException

263. What will be the output of the following code? `System.out.println('A' + 1);`

65

'A1'

'A'

66

264. Which of the following interfaces is used to create a queue in Java?

Queue

Both A and B

List

Deque

265. Which of the following statements about interfaces in Java is false?

A class can implement multiple interfaces

Interfaces can contain method implementations

Interfaces can extend multiple other interfaces

Interfaces cannot have constructors

266. Which of the following is used to perform type conversion in Java?

Casting

Type coercion

Type conversion

All of the above

267. Which of the following is not a valid way to compare two strings in Java?

string1.compareTo(string2)

string1.equalsIgnoreCase(string2)

string1.equals(string2)

string1 == string2

268. Which method is used to get the class type of an object?

typeof

getClass()

ClassName.getClass()

instanceof

269. What will be the output of the following code? `System.out.println(2 + 2 + "4");`

4

24

44

Error

270. What is the purpose of the `this` keyword in Java?

To refer to the current object

To refer to parent class

To access static methods

To create new instances of a class

271. Which of the following classes cannot be inherited?

String

Thread

Integer

Object

272. Which of the following keywords is used to define a block of code that will always be executed, regardless of whether an exception is thrown?

finally

throw

catch

try

273. What will be the output of the following code? `int x = 5; System.out.println(x++);`

Error

5

0

6

274. Which of the following is a valid statement to create an object of a class?

ClassName obj = new ClassName;

ClassName obj = new ClassName();

ClassName obj = ClassName.new();

ClassName obj = ClassName();

275. Which of the following keywords is used to declare a constant variable in Java?

constant

static

static final

final

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