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JAVA-PROGRAMMING PRACTICE SET 1

Java Programming Interview Questions

Prepare for Java Interview

1 / 25

Which access modifier should be used to make a variable or method accessible only within the same package?

public

private

protected

Default (package-private)

2 / 25

What is the difference between a class and an object in Java?

A class is a blueprint to create objects, while an object is an instance of a class.

A class is a data type, while an object is a variable.

A class is a method, while an object is a property.

A class is a parent, while an object is a child.

3 / 25

What is the role of the equals() method in Java?

It is used to compare the references of two objects for equality.

It is used to compare the values of two objects for equality.

It is used to convert an object to a primitive data type.

It is used to check if an object is an instance of a particular class.

4 / 25

What is the purpose of the interface keyword in Java?

It is used to define a class with no implementation details.

It is used to define a class with a single method.

It is used to define a class that cannot be instantiated directly but can be subclassed.

It is used to define a set of method signatures that any class implementing the interface must provide.

5 / 25

What is the difference between ArrayList and LinkedList in Java?

ArrayList is a linear data structure, while LinkedList is a hierarchical data structure.

ArrayList uses a linked list to store elements, while LinkedList uses an array.

ArrayList allows faster access to elements using indexing, while LinkedList provides faster insertions and deletions.

ArrayList implements the List interface, while LinkedList implements the Collection interface.

6 / 25

Which keyword is used to prevent a class from being subclassed in Java?

final

static

abstract

sealed

7 / 25

What is the purpose of the super keyword in Java?

It refers to the current instance of the class and is used to access its own methods and variables.

It refers to the parent class and is used to access its methods and variables.

It is used to create an object of a class.

It is used to define a static method.

8 / 25

What are the four fundamental principles of Object-Oriented Programming (OOP)?

Data Hiding, Abstraction, Polymorphism, Inheritance

Encapsulation, Data Hiding, Abstraction, Polymorphism

Encapsulation, Abstraction, Inheritance, Polymorphism

Abstraction, Inheritance, Encapsulation, Data Hiding

9 / 25

What is polymorphism in Java?

Polymorphism is achieved through the use of inheritance and overriding.

Polymorphism is the ability of an object to take on different forms.

Polymorphism allows us to write code that is more generic and flexible.

Polymorphism allows us to reuse code more effectively.

10 / 25

What is encapsulation in Java?

Encapsulation allows us to control the way in which the data of an object is accessed.

Encapsulation allows us to protect the data of an object from unauthorized access.

Encapsulation is achieved by declaring the variables and methods of an object as private.

Encapsulation is the process of hiding the implementation details of an object from the outside world.

11 / 25

What is the difference between a local variable and an instance variable in Java?

A local variable is destroyed when the method is exited, while an instance variable is destroyed when the object is garbage collected.

A local variable is declared within a method, while an instance variable is declared within a class.

A local variable is created using the final keyword, while an instance variable is not created with the final keyword.

A local variable can be accessed by all methods in the class, while an instance variable can only be accessed by the methods in the class that declared it.

12 / 25

What is the difference between a class and an interface in Java?

A class can be extended, while an interface cannot.

A class can be implemented, while an interface cannot.

A class can have both abstract and concrete methods, while an interface can only have abstract methods.

A class is a blueprint for an object, while an interface is a contract that an object must implement.

13 / 25

What is the difference between an abstract method and a concrete method in Java?

An abstract method must be overridden by a subclass, while a concrete method does not need to be overridden.

An abstract method is a method that has no implementation, while a concrete method has an implementation.

An abstract method cannot be called directly, while a concrete method can be called directly.

An abstract method is declared with the abstract keyword, while a concrete method is not declared with the abstract keyword.

14 / 25

What is the difference between a static and a non-static block in Java?

A static block is declared in the class definition, while a non-static block is declared inside a method.

A static block cannot access non-static variables, while a non-static block can.

A static block can access static variables, while a non-static block cannot.

A static block is executed once when the class is loaded, while a non-static block is executed each time an object of the class is created.

15 / 25

What is the difference between a constructor and a method in Java?

A constructor is declared in the class definition, while a method is declared outside the class definition.

A constructor is used to initialize an object, while a method is used to perform an operation.

A constructor is called automatically when an object is created, while a method must be called explicitly.

A constructor cannot return a value, while a method can return a value.

16 / 25

What is the purpose of the finally block in Java?

It is used to print the stack trace of an exception.

It is used to close resources that were opened in the try block.

It is used to catch exceptions that are not caught in the try block.

It is used to execute code that must be executed regardless of whether an exception is thrown or not.

17 / 25

What is the difference between an abstract class and an interface in Java?

An abstract class can have abstract methods, while an interface cannot.

An abstract class can have concrete methods, while an interface cannot.

An abstract class can be extended, while an interface cannot.

An interface can be implemented, while an abstract class cannot.

18 / 25

What is the difference between static and non-static methods in Java?

Static methods can be called without creating an object of the class, while non-static methods cannot.

Static methods are stored in the class itself, while non-static methods are stored in the object.

Static methods can access static variables, while non-static methods cannot.

Static methods cannot be overridden, while non-static methods can be overridden.

19 / 25

What is the purpose of the main() method in Java?

It is the entry point for all Java programs.

It is used to initialize the class.

It is used to call the other methods in the class.

It is used to print the output of the program.

20 / 25

What is the difference between a class and an object in Java?

A class is a blueprint for an object, while an object is an instance of a class.

A class is a data type, while an object is a variable.

A class is a method, while an object is a function.

A class is a constructor, while an object is a destructor.

21 / 25

What is the output of the following code?

String str = “Hello, world!”;

System.out.println(str.substring(5, 10));

world

Hello

22 / 25

Which of the following is not a keyword in Java?

class

while

for

23 / 25

What is the output of the following code?

int x = 10;

int y = x++;

System.out.println(x + y);

24 / 25

What is the size of a float in Java?

4 bytes

8 bytes

16 bytes

32 bytes

25 / 25

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

int

char

float

string

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JAVA-PROGRAMMING PRACTICE SET 2

Java Programming Set 2

Java Programming Practice Set 2

1 / 25

Which keyword is used to establish inheritance in Java?

extends

implements

derives

inherits

2 / 25

What is a superclass in Java?

A class that inherits properties from another class

A class that does not have any methods

A built-in Java class

A class with private methods

3 / 25

What does inheritance enable in Java?

Code duplication

Reusability of code and implementation of IS-A relationship

Creation of new data types

Polymorphism

4 / 25

What is a constructor in Java?

A method used to perform mathematical calculations.

A method that is used to initialize an object.

A method that returns a value.

A method that is called when an object is deleted.

5 / 25

How is method overloading defined?

Defining multiple methods with the same name but different return types.

Defining multiple methods with the same name and parameters but different return types.

Defining multiple methods with the same name and parameters.

Defining multiple methods with the same name but different access modifiers.

6 / 25

What is the purpose of the `return` statement in a method?

It defines the method's return type.

It specifies the parameters of the method.

It ends the method's execution and returns a value to the caller.

It indicates that the method cannot be overridden.

7 / 25

Which keyword is used to define a method in Java?

method

def

void

func

8 / 25

Which statement correctly declares and initializes an array of integers with values 1, 2, and 3?

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

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

int arr[] = (1, 2, 3);

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

9 / 25

Which data type is used to store a decimal number with 15-17 significant digits?

float

int

double

long

10 / 25

What is the result of `10 / 3` in Java?

3.3333

3.0

3.1

11 / 25

How many times does the following loop iterate?

for (int i = 0; i <= 5; i++) { System.out.println(i); }

4 times

5 times

6 times

7 times

12 / 25

What is the output of the following code snippet?

int x = 5;
if (x > 10) {
System.out.println(“A”);
} else if (x > 3) {
System.out.println(“B”);
} else {
System.out.println(“C”);
}

B C

13 / 25

Which of the following statements is true regarding the `switch` statement in Java?

It can only handle int values.

It is an alternative to the if statement.

The default case is optional.

It supports floating-point values.

14 / 25

Which loop structure is best suited for situations where the loop body should execute at least once?

for loop

while loop

do-while loop

All loops are equally suited.

15 / 25

What is the purpose of the `break` statement in a loop?

It terminates the loop entirely.

It skips the rest of the current iteration and proceeds to the next iteration.

It restarts the loop from the beginning.

It increments the loop counter.

16 / 25

Which concept prevents the modification of certain class members from outside the class?

Inheritance

Polymorphism

Encapsulation

Abstraction

17 / 25

What does the keyword `super` refer to in Java?

The superclass of a class

A built-in Java method

A Java keyword used for loops

A reserved identifier

18 / 25

Which access modifier provides the widest visibility for class members?

private

protected

default

public

19 / 25

What is the concept of allowing multiple classes to share the same method signature?

Inheritance

Polymorphism

Abstraction

Encapsulation

20 / 25

In Java, a class can have multiple:

Constructors

Main methods

Superclasses

Private methods

21 / 25

What is the entry point of a Java program?

start()

run()

main()

begin()

22 / 25

Which data type is used to represent a single Unicode character in Java?

char

Character

string

CHAR

23 / 25

What is the default value of an instance variable in Java if not explicitly initialized?

null

false

Depends on the variable type

24 / 25

Which of the following is the correct syntax to define a class in Java?

class MyClass { }

new class MyClass() { }

class { } MyClass

MyClass = class { }

25 / 25

What is Java primarily known for?

Being a scripting language

High-performance mathematical calculations

Platform independence

Data visualization

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JAVA-PROGRAMMING PRACTICE SET 3

0

Java Programming Practice Set 3

Test Your Java Skills on OOP’s Concept

1 / 25

What is the purpose of the “static” keyword in Java?

To create a new instance of a class.

To access class-level variables and methods.

To call a superclass constructor.

To define a subclass.

2 / 25

Which of the following is a feature of encapsulation in Java?

It allows access to all class members from outside the class.

It restricts access to class members from outside the class.

It enforces method overriding in subclasses.

It allows multiple inheritance.

3 / 25

What is the role of a constructor in a Java class?

To create an object of the class.

To define the methods of the class.

To store data in the class.

To access the superclass.

4 / 25

Which keyword is used to declare a constant in Java?

constant

final

const

static

5 / 25

Which of the following is not a valid data type in Java?

int

float

char

decimal

6 / 25

What is the purpose of the “this” keyword in Java?

To create a new instance of a class.

To access the current object's properties and methods.

To call a superclass constructor.

To define a subclass.

7 / 25

Which of the following is a valid way to create an object in Java?

MyClass myObj = new MyClass();

MyClass myObj = MyClass();

MyClass myObj = createObject(MyClass);

MyClass myObj = createObject();

8 / 25

Which keyword is used to exit from a loop prematurely in Java?

break

exit

return

continue

9 / 25

What is the default value of an instance variable in Java if it is not initialized?

0

1

null

It depends on the data type

10 / 25

In Java, which keyword is used to prevent a class from being inherited by other classes?

private

final

static

protected

11 / 25

Which of the following is a runtime polymorphism example in Java?

Method Overloading

Method Overriding

Constructor Overloading

Operator Overloading

12 / 25

What is the purpose of the “super” keyword in Java?

To create an instance of a class.

To call a superclass constructor or method.

To access a static variable.

To define a subclass.

13 / 25

What is method overloading in Java?

Defining multiple methods with the same name in the same class.

Defining multiple methods with different names in the same class.

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

Defining multiple methods with the same name and same parameters in the same class.

14 / 25

Which of the following statements about abstract classes in Java is true?

You can create instances of an abstract class.

Abstract classes cannot have constructors.

Abstract classes can have both abstract and concrete methods.

Abstract classes cannot be extended by other classes.

15 / 25

In Java, which keyword is used to implement multiple inheritance using interfaces?

extends

implements

inherits

extends and implements both

16 / 25

Which of the following is not a valid access modifier in Java?

public

private

final

protected

17 / 25

Which keyword in Java is used to create an instance of a class?

instance

create

new

make

18 / 25

What is the process of defining multiple methods in a class with the same name but different parameters called?

Inheritance

Polymorphism

Encapsulation

Abstraction

19 / 25

Which principle of OOP suggests that an object should only expose the necessary methods and properties, hiding the internal details?

Inheritance

Polymorphism

Abstraction

Encapsulation

20 / 25

Which keyword in Java is used to call a superclass constructor from a subclass?

super

this

base

parent

21 / 25

In Java, what is the access modifier that restricts access to members within the same package?

private

protected

default

public

22 / 25

Which OOP concept allows you to define a new class based on an existing class?

Inheritance

Encapsulation

Polymorphism

Abstraction

23 / 25

What is an object in Java?

A method

An instance of a class

A variable

A loop

24 / 25

In Java, what is a class?

A blueprint for objects

An object itself

A data type

A method

25 / 25

What is the main advantage of using Object-Oriented Programming (OOP)?

Code reusability

Smaller code size

Faster execution

Easier debugging

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Interview Questions

JAVA-PROGRAMMING PRACTICE SET 1

JAVA-PROGRAMMING PRACTICE SET 2

Which keyword is used to establish inheritance in Java?

What is a superclass in Java?

What does inheritance enable in Java?

What is a constructor in Java?

How is method overloading defined?

What is the purpose of the return statement in a method?

Which keyword is used to define a method in Java?

Which statement correctly declares and initializes an array of integers with values 1, 2, and 3?

Which data type is used to store a decimal number with 15-17 significant digits?

What is the result of 10 / 3 in Java?

How many times does the following loop iterate?

What is the output of the following code snippet?

Which of the following statements is true regarding the switch statement in Java?

Which loop structure is best suited for situations where the loop body should execute at least once?

What is the purpose of the break statement in a loop?

Which concept prevents the modification of certain class members from outside the class?

What does the keyword super refer to in Java?

Which access modifier provides the widest visibility for class members?

What is the concept of allowing multiple classes to share the same method signature?

In Java, a class can have multiple:

What is the entry point of a Java program?

Which data type is used to represent a single Unicode character in Java?

What is the default value of an instance variable in Java if not explicitly initialized?

Which of the following is the correct syntax to define a class in Java?

What is Java primarily known for?

JAVA-PROGRAMMING PRACTICE SET 3

What is the purpose of the “static” keyword in Java?

Which of the following is a feature of encapsulation in Java?

What is the role of a constructor in a Java class?

Which keyword is used to declare a constant in Java?

Which of the following is not a valid data type in Java?

What is the purpose of the “this” keyword in Java?

Which of the following is a valid way to create an object in Java?

Which keyword is used to exit from a loop prematurely in Java?

What is the default value of an instance variable in Java if it is not initialized?

In Java, which keyword is used to prevent a class from being inherited by other classes?

Which of the following is a runtime polymorphism example in Java?

What is the purpose of the “super” keyword in Java?

What is method overloading in Java?

Which of the following statements about abstract classes in Java is true?

In Java, which keyword is used to implement multiple inheritance using interfaces?

Which of the following is not a valid access modifier in Java?

Which keyword in Java is used to create an instance of a class?

What is the process of defining multiple methods in a class with the same name but different parameters called?

Which principle of OOP suggests that an object should only expose the necessary methods and properties, hiding the internal details?

Which keyword in Java is used to call a superclass constructor from a subclass?

In Java, what is the access modifier that restricts access to members within the same package?

Which OOP concept allows you to define a new class based on an existing class?

What is an object in Java?

In Java, what is a class?

What is the main advantage of using Object-Oriented Programming (OOP)?

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What is the purpose of the `return` statement in a method?

What is the result of `10 / 3` in Java?

Which of the following statements is true regarding the `switch` statement in Java?

What is the purpose of the `break` statement in a loop?

What does the keyword `super` refer to in Java?

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