Accessing Class Members: A Comprehensive Guide for Object-Oriented Programming

Question 1

To access the instance variable 'name' of the 'Person' class, which syntax is correct?

Accepted Answer

person.name

Answer

Person.name

Answer

name.person

Answer

this.name

Question 2

Which operator is used to access instance variables and methods of a class?

Accepted Answer

The dot operator (.)

Answer

::

Question 3

What is the difference between an instance variable and a class variable?

Accepted Answer

Instance variables belong to an object, while class variables belong to the class itself.

Answer

Class variables belong to an object, while instance variables belong to the class itself.

Question 4

Which of the following is a valid way to access an instance method of a class?

Accepted Answer

Using the dot operator and specifying the method name followed by parentheses.

Answer

className.methodName()

Question 5

What is the purpose of the 'this' keyword in Java?

Accepted Answer

To refer to the current object.

Answer

To refer to the class itself.

Question 6

Which of the following is a characteristic of encapsulation?

Accepted Answer

Hiding the implementation details of a class.

Answer

Allowing direct access to instance variables.

Question 7

What is the difference between a getter and a setter method?

Accepted Answer

Getter methods retrieve values, while setter methods modify values.

Answer

Getter methods modify values, while setter methods retrieve values.

Question 8

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

Accepted Answer

default (package-private)

Answer

private

Question 9

Which of the following is a valid way to create a final variable in Java?

Accepted Answer

Using the 'final' keyword before the variable declaration and initialization.

Answer

int final varName = 5;

Question 10

Which operator is used to access instance variables and methods of a class?

Accepted Answer

.

Answer

->

Answer

::

Answer

*

Question 11

Which of the following is NOT a valid way to access a static method of a class?

Accepted Answer

this.methodName()

Answer

ClassName.methodName()

Answer

objectReference.methodName()

Answer

methodName()

Question 12

Consider the following code: 
 class MyClass { public static int count = 0; } 
 MyClass.count++; 
 What is the value of MyClass.count after the statement executes?

Accepted Answer

1

Answer

0

Answer

Cannot increment static variable

Answer

Error: count is not accessible

Question 13

Which access modifier allows access to class members from subclasses in other packages?

Accepted Answer

protected

Answer

private

Answer

public

Answer

default

Question 14

Which of the following correctly assigns a value to the 'name' instance variable of an object?

Accepted Answer

objectReference.name = "John";

Answer

objectReference = new String("John");

Answer

this.name = "John";

Answer

name("John");

Question 15

Which keyword is used to invoke a constructor from another constructor?

Accepted Answer

super

Answer

new

Answer

this

Answer

extends

Question 16

Consider the following code: 
 class MyClass { public synchronized void method() { // ... } } 
 What is the purpose of the 'synchronized' keyword in this code?

Accepted Answer

To prevent multiple threads from accessing the method concurrently

Answer

To make the method execute faster

Answer

To allow only one thread to access the method

Answer

To ensure the method always returns the same value

Question 17

Which access modifier is most restrictive, allowing access only within the class itself?

Accepted Answer

private

Answer

public

Answer

protected

Answer

default

Question 18

Consider the following code: 
 class MyClass { private int x; public MyClass(int x) { this.x = x; } } 
 What is the purpose of the constructor in this code?

Accepted Answer

To initialize the instance variable 'x' with the provided value

Answer

To set the class name

Answer

To create a new instance of the class

Answer

To define the behavior of the class

Question 19

Which operator is employed to access class members?

Accepted Answer

.

Answer

->

Answer

::

Answer

*

Question 20

Define an instance variable.

Accepted Answer

A variable defined within a class

Answer

A variable defined within a method

Answer

A variable defined outside a class

Answer

A variable defined within an interface

Question 21

Which syntax is correct for accessing an instance variable?

Accepted Answer

objectName.variableName

Answer

className.variableName

Answer

this.variableName

Answer

variableName

Question 22

What is the primary purpose of a getter method?

Accepted Answer

To retrieve the value of an instance variable

Answer

To modify the value of an instance variable

Answer

To alter the state of an object

Answer

To generate a new object

Question 23

Which syntax is valid for invoking a method on an object?

Accepted Answer

objectName.methodName()

Answer

className.methodName()

Answer

this.methodName()

Answer

methodName()

Question 24

Explain the distinction between public and private class members.

Accepted Answer

Public members are accessible from anywhere, while private members are restricted to within the class.

Answer

Private members are accessible from anywhere, while public members are restricted to within the class.

Answer

Public members are inherited by subclasses, but private members are not.

Answer

Private members are inherited by subclasses, but public members are not.

Question 25

What is the primary function of the 'this' keyword?

Accepted Answer

To reference the current object

Answer

To access static members of a class

Answer

To create a new object

Answer

To invoke a method on an object

Question 26

Which practice is recommended for accessing class members?

Accepted Answer

Favor the use of getter and setter methods

Answer

Directly access private members from outside the class

Answer

Declare all class members as public

Answer

Explicitly use the 'this' keyword

Question 27

How can you safeguard class members from unauthorized access?

Accepted Answer

Employ access modifiers

Answer

Implement encryption

Answer

Make the class immutable

Answer

Utilize reflection

Question 28

Which operator is used to access instance variables and methods of a class?

Accepted Answer

.

Answer

&

Answer

*

Answer

+

Question 29

Where are instance variables stored in an object-oriented programming context?

Accepted Answer

In the object's memory

Answer

In the class definition

Answer

In the method implementation

Answer

In the constructor

Question 30

Which keyword is used to access methods defined in a superclass?

Accepted Answer

super

Answer

override

Answer

this

Answer

extends

Question 31

What is the primary purpose of the 'this' keyword in object-oriented programming?

Accepted Answer

To refer to the current object

Answer

To access static methods

Answer

To call a constructor

Answer

To declare a new variable

Question 32

Explain the key difference between an instance variable and a static variable in object-oriented programming.

Accepted Answer

Instance variables are specific to each object, while static variables are shared among all objects

Answer

Static variables are specific to each object, while instance variables are shared among all objects

Answer

There is no difference between instance variables and static variables

Answer

Instance variables are declared with the 'static' keyword, while static variables are not

Question 33

What is the primary purpose of a constructor in object-oriented programming?

Accepted Answer

To initialize an object's state

Answer

To define the object's behavior

Answer

To create a new object

Answer

To access class members

Question 34

In object-oriented programming, how does 'encapsulation' control access to class members?

Accepted Answer

Encapsulation restricts access to class members through defined interfaces.

Answer

Encapsulation allows unrestricted access to class members for enhanced organization.

Answer

Encapsulation has no impact on accessing class members, which can be accessed directly.

Answer

Encapsulation grants access to class members to any object within the same package, regardless of access modifiers.

Question 35

In Java, which operator is used to access class members, like instance variables and methods?

Accepted Answer

Dot operator (.)

Answer

Arrow operator (->)

Answer

Colon operator (:)

Answer

Parentheses operator ()

Question 36

What's the purpose of instance variables in a class?

Accepted Answer

To define the unique state of individual objects

Answer

To store global data shared across all objects

Answer

To implement class methods and behaviors

Answer

To provide access to external resources

Question 37

How do you call a class method using the dot operator in Java?

Accepted Answer

object.method()

Answer

method(object)

Answer

object::method

Answer

method::object()

Question 38

What's the key difference between public and private class members?

Accepted Answer

Public members can be accessed from anywhere, while private members can only be accessed within the class

Answer

Private members can be accessed from anywhere, while public members can only be accessed within the class

Answer

Public members are visible to subclasses, while private members are not

Answer

Private members are visible to subclasses, while public members are not

Question 39

Which of the following is NOT a valid scope for a class member?

Accepted Answer

Global

Answer

Instance

Answer

Static

Answer

Protected

Question 40

In Java, which syntax is correct to access instance variable 'x'?

Accepted Answer

object.x

Answer

x()

Answer

x.object

Answer

object->x

Question 41

In Java, what is the primary purpose of the 'this' keyword within a method?

Accepted Answer

To represent the current object

Answer

To pass the object as an argument to another method

Answer

To access static members of the class

Answer

To create a new instance of the class

Question 42

In Java, which access modifier allows a subclass to access private members of its superclass?

Accepted Answer

protected

Answer

private

Answer

default

Answer

public

Question 43

What is the key difference between an instance method and a static method in Java?

Accepted Answer

Instance methods operate on object state, while static methods operate on class state.

Answer

Static methods are inherited by subclasses, while instance methods are not.

Answer

Instance methods can be called from anywhere, while static methods must be called from within the class.

Question 44

Which of the following is NOT a potential advantage of encapsulation?

Accepted Answer

Increased flexibility

Answer

Enhanced maintainability

Answer

Improved security

Answer

Reduced coupling

Question 45

In Java, how can you ensure a class method is only accessible to its subclasses?

Accepted Answer

Declare the method as 'protected'

Answer

Declare the method as 'private'

Answer

Declare the method as 'public'

Question 46

Which of the following syntaxes correctly accesses the `name` instance variable of the `student` object?

Accepted Answer

student.name

Answer

student[name]

Answer

student ->name

Answer

name.student

Question 47

Consider the following code: `class Person { private String name; public void setName(String name) { this.name = name; } }`. Which method invocation correctly sets the `name` instance variable?

Accepted Answer

person.setName("John")

Answer

person.name = "John"

Answer

Person.setName("John")

Question 48

Which of the following method calls correctly invokes the `greet()` method of the `student` object?

Accepted Answer

student.greet()

Answer

student greet()

Answer

greet(student)

Answer

Student.greet()

Question 49

Consider the code snippet: `class Car { private int speed; public int getSpeed() { return speed; } }`. Which expression correctly retrieves the `speed` instance variable of a `Car` object?

Accepted Answer

car.getSpeed()

Answer

getSpeed(car)

Answer

Car.getSpeed()

Answer

car.speed

Question 50

Which of the following statements correctly modifies the `age` instance variable of the `person` object?

Accepted Answer

person.age = 25

Answer

age.person = 25

Answer

setAge(person, 25)

Answer

person setAge(25)

Question 51

Consider the following code: `class Employee { private String name; private int salary; public Employee(String name, int salary) { this.name = name; this.salary = salary; } public String toString() { return name + " earns " + salary; } }`. Which expression correctly creates an `Employee` object with the specified `name` and `salary`?

Accepted Answer

new Employee("John", 50000)

Answer

Employee("John", 50000)

Answer

Employee(new John, 50000)

Answer

new Employee(John, 50000)

Question 52

Which of the following is a valid way to access the static variable `count` from the `Counter` class?

Accepted Answer

Counter.count

Answer

Counter[count]

Answer

count.Counter

Answer

Counter ->count

Question 53

Consider the code snippet: `class Utility { public static int sum(int a, int b) { return a + b; } public static void main(String[] args) { int result = Utility.sum(5, 10); } }`. Which method call correctly invokes the `sum()` method?

Accepted Answer

Utility.sum(5, 10)

Answer

Utility sum(5, 10)

Answer

sum.Utility(5, 10)

Answer

sum(Utility, 5, 10)

Question 54

Which of the following statements correctly accesses the `MAX_VALUE` constant from the `Integer` class?

Accepted Answer

Integer.MAX_VALUE

Answer

Integer ->MAX_VALUE

Answer

MAX_VALUE.Integer

Answer

Integer[MAX_VALUE]

Question 55

Consider the following code: `class Shape { public static double calculateArea() { return 0.0; } } class Circle extends Shape { public static double calculateArea(double radius) { return Math.PI * radius * radius; } }`. Which method call correctly calculates the area of a circle with radius 5?

Accepted Answer

Circle.calculateArea(5.0)

Answer

Shape.calculateArea(5.0)

Answer

Circle calculateArea(5.0)

Answer

calculateArea(Circle, 5.0)