Java

Question 1

What is the main purpose of Java’s garbage collector?

Answer 1

To automatically manage memory by reclaiming memory used by objects that are no longer referenced.

Question 2

True or False: Java supports multiple inheritance through classes.

Answer 2

False

Question 3

What keyword is used to inherit a class in Java?

Answer 3

extends

Question 4

Fill in the blank: In Java, the _______ keyword is used to declare a constant.

Answer 4

final

Question 5

Which of the following is a valid way to declare an array in Java? (A) int arr[]; (B) int[] arr; (C) Both A and B

Answer 5

C

Question 6

What is the default value of a boolean variable in Java?

Answer 6

false

Question 7

What does JVM stand for?

Answer 7

Java Virtual Machine

Question 8

True or False: An interface can contain method implementations in Java.

Answer 8

False

Question 9

What is the purpose of the ‘synchronized’ keyword in Java?

Answer 9

To control access to a method or block by multiple threads.

Question 10

What is the output of the following code: System.out.println(1 + 1 + ‘1’);? (A) 21 (B) 11 (C) 2

Answer 10

21

Question 11

Which collection class allows duplicate elements in Java?

Answer 11

ArrayList

Question 12

What is the primary function of the ‘try-catch’ block?

Answer 12

To handle exceptions that may occur during program execution.

Question 13

Fill in the blank: A _______ is a blueprint for creating objects in Java.

Answer 13

class

Question 14

What is method overloading?

Answer 14

Defining multiple methods with the same name but different parameters in the same class.

Question 15

True or False: Java provides a mechanism called ‘autoboxing’ for converting primitive types to their corresponding wrapper classes.

Answer 15

True

Question 16

What is the purpose of the ‘this’ keyword in Java?

Answer 16

To refer to the current object instance.

Question 17

Which of the following is NOT a primitive data type in Java? (A) int (B) String (C) boolean

Answer 17

B

Question 18

What does the ‘transient’ keyword indicate in Java?

Answer 18

That a field should not be serialized.

Question 19

What is a ‘static’ method?

Answer 19

A method that belongs to the class rather than any specific instance.

Question 20

Fill in the blank: Java uses _______ to achieve platform independence.

Answer 20

bytecode

Question 21

What is the difference between ‘== ‘ and ‘.equals()’ in Java?

Answer 21

’==’ checks reference equality, while ‘.equals()’ checks for value equality.

Question 22

True or False: A Java interface can extend multiple other interfaces.

Answer 22

True

Question 23

What is the purpose of the ‘finalize()’ method in Java?

Answer 23

To perform cleanup before an object is garbage collected.

Question 24

What is the output of the following code: System.out.println(5 / 2);?

Answer 24

2

Question 25

Which exception is thrown when a program attempts to access an array with an illegal index?

Answer 25

ArrayIndexOutOfBoundsException

Question 26

What is a 'constructor' in Java?

Answer 26

A special method used to initialize objects.

Question 27

Fill in the blank: The _______ block is used to execute code regardless of whether an exception is thrown or not.

Answer 27

finally

Question 28

What does the 'volatile' keyword do in Java?

Answer 28

It indicates that a variable may be changed by different threads.

Question 29

True or False: Java supports operator overloading.

Answer 29

False

Question 30

What is the difference between 'List' and 'Set' in Java Collections Framework?

Answer 30

'List' allows duplicates and maintains order, while 'Set' does not allow duplicates and does not guarantee order.

Question 31

What is the purpose of the 'instanceof' operator?

Answer 31

To test whether an object is an instance of a specific class or interface.

Question 32

What is the default access modifier for class members in Java?

Answer 32

Package-private

Question 33

Which keyword is used to create an anonymous inner class in Java?

Answer 33

new

Question 34

Fill in the blank: The Java Development Kit (JDK) includes a _______ for compiling Java source code.

Answer 34

compiler

Question 35

What is a 'Java Bean'?

Answer 35

A reusable software component that follows specific conventions for property management.

Question 36

True or False: Java supports multiple inheritance through interfaces.

Answer 36

True

Question 37

What is the purpose of the 'super' keyword?

Answer 37

To refer to the superclass of the current object.

Question 38

Which of the following is a feature of Java? (A) Platform independence (B) Automatic memory management (C) Both A and B

Answer 38

C

Question 39

What does 'JAR' stand for in Java?

Answer 39

Java Archive

Question 40

What is the significance of the 'main' method in Java?

Answer 40

It serves as the entry point for any Java application.

Question 41

Fill in the blank: The _______ package contains the Java Collections Framework.

Answer 41

java.util

Question 42

What is the purpose of 'Java Reflection'?

Answer 42

To inspect classes, interfaces, fields, and methods at runtime without knowing the names of the classes.

Question 43

True or False: The 'String' class in Java is mutable.

Answer 43

False

Question 44

What is the role of a 'Comparator' in Java?

Answer 44

To define a custom sorting order for objects.

Question 45

What is the purpose of the 'assert' statement in Java?

Answer 45

To provide a means for debugging by testing assumptions in the code.

Question 46

What is a 'static block' in Java?

Answer 46

A block of code that runs when the class is loaded into memory.

Question 47

Fill in the blank: Java uses _______ to manage access control for classes and members.

Answer 47

access modifiers

Question 48

What is the primary use of 'Java Annotations'?

Answer 48

To provide metadata about a program element.

Question 49

What is a 'Checked Exception'?

Answer 49

An exception that must be either caught or declared in the method signature.

Question 50

True or False: The 'StringBuilder' class is synchronized.

Answer 50

False

Question 51

What is the purpose of the 'volatile' keyword?

Answer 51

To ensure visibility of changes to variables across threads.

Question 52

Which Java keyword is used to create a new thread?

Answer 52

Thread

Question 53

Fill in the blank: A _______ is used to handle a group of related exceptions in Java.

Answer 53

catch block

Question 54

What is the difference between 'HashMap' and 'TreeMap'?

Answer 54

'HashMap' is unordered and allows null keys, while 'TreeMap' is ordered and does not allow null keys.

Question 55

What does 'JVM' do when it encounters a 'ClassNotFoundException'?

Answer 55

It indicates that the Java Virtual Machine cannot find a class that is being referenced.

Question 56

What is the output of the expression '10 % 3' in Java?

Answer 56

1

Question 57

Fill in the blank: The _______ interface is used to implement a callback mechanism in Java.

Answer 57

Runnable

Question 58

What is the purpose of the 'default' keyword in interfaces?

Answer 58

To provide a default implementation for a method in an interface.

Question 59

True or False: The 'main' method must always be declared as public.

Answer 59

True

Question 60

What is the function of the 'Thread.sleep()' method?

Answer 60

To pause the execution of the current thread for a specified time.

Question 61

What does the 'final' keyword indicate when used with a class?

Answer 61

That the class cannot be subclassed.

Question 62

Fill in the blank: An _______ is a template for creating objects and contains methods and variables.

Answer 62

object

Question 63

What is the role of 'JavaFX'?

Answer 63

To provide a platform for creating rich internet applications.

Question 64

What is the purpose of the 'volatile' keyword in concurrent programming?

Answer 64

To ensure that updates to a variable are visible to other threads.

Question 65

What happens when you try to access an index of an array that is out of bounds?

Answer 65

ArrayIndexOutOfBoundsException is thrown.

Question 66

Fill in the blank: Java uses _______ to manage the lifecycle of an application.

Answer 66

threads

Question 67

What is the difference between 'abstract class' and 'interface'?

Answer 67

'Abstract class' can have both abstract and concrete methods, while 'interface' can only have abstract methods (until Java 8).

Question 68

What is 'Java Streams'?

Answer 68

A feature that allows functional-style operations on collections of objects.

Question 69

True or False: A constructor can have a return type.

Answer 69

False

Question 70

What is the role of the 'java.lang' package?

Answer 70

It contains fundamental classes that are essential for Java programming.

Question 71

What is the output of the following code: System.out.println(3 + 4 + '7');?

Answer 71

74

Question 72

Fill in the blank: The _______ method is called when an exception is not caught.

Answer 72

printStackTrace

Question 73

What is the main purpose of the 'synchronized' keyword?

Answer 73

To prevent thread interference by allowing only one thread to access a block of code at a time.

Question 74

What does the term 'boxing' refer to in Java?

Answer 74

The conversion of a primitive type to its corresponding wrapper class.

Question 75

True or False: A synchronized block is less flexible than synchronized methods.

Answer 75

True