Category: Object Oriented Programming Objective Questions

Object Oriented Programming (OOPs) Multiple Choice Questions & Answers (MCQs) on “Inbuilt Classes”.

1. What are inbuilt classes?
a) The predefined classes in a language
b) The classes that are defined by the user
c) The classes which are meant to be modified by the user
d) The classes which can’t be used by the user
Answer: a
Clarification: The classes that are already provided in a programming language for use are inbuilt classes. These classes provide some functions or objects that can be used by the programmer for easier code.

2. Inbuilt class __________________________
a) Must be included before use
b) Are not necessary to be included for use
c) Are used by the compiler only
d) Can be modified by programmer always
Answer: a
Clarification: The inbuilt classes must be included in the program. Whenever some functions are used, they must have a declaration before use. The same is the case with classes.

3. What doesn’t inbuilt classes contain?
a) Function prototype
b) Function declaration
c) Function definitions
d) Objects
Answer: c
Clarification: The classes contain the definitions of the special functions that are provided for the programmers use. Those functions can be used to make the programming easy and to reuse the already existing code.

4. Which among the following not an inbuilt class in C++?
a) System
b) Color
c) String
d) Functions
Answer: d
Clarification: There is no inbuilt class named function in java. The others are classes already provided in java. All those classes contain some special functions to be used in programming.

5. What is the InputStream class meant for?
a) To handle all input streams
b) To handle all output streams
c) To handle all input and output streams
d) To handle only input from file
Answer: a
Clarification: The InputStream is an inbuilt class which is used to handle all the tasks related to input handling. This class extends input from keyboard or file or any other possible input stream.

6. Which statement is true for the Array class?
a) Arrays can have variable length
b) The length array can be changed
c) Each class has an associated Array class
d) Arrays can contain different type of values
Answer: c
Clarification: The Array class is associated with all the other classes. This gives us the flexibility to declare an array of any type. The index goes from 0 to n, where n is some fixed size for array.

7. What is the use of Math class?
a) To use the mathematical functions with strings
b) To use the mathematical functions
c) To suppress the use of mathematical functions
d) To complex the calculations
Answer: b
Clarification: The Math class is provided with some special functions. These functions can be used to calculate and get result of some special and usual mathematical functions. We don’t have to write the code to calculate the trigonometric function results, instead we can use Math functions.

8. DataInputStream is derived from ______________________
a) StreamingInput
b) StreamedInput
c) StreameInput
d) StreamInput
Answer: d
Clarification: The DataInputStream is more specific class for operating on specific type of data inputs. This is used to read data of specific type. The same can be used to read data in a specific format.

9. Which attribute can be used to get the size of an array?
a) Size.Array
b) Array.Size
c) Array_name.length
d) length.Array_name
Answer: c
Clarification: The array name is given of which the length have to be calculated. The array length is stored in the attribute length. Hence we access it using dot operator.

10. Number class can’t manipulate ____________________
a) Integer values
b) Float values
c) Byte values
d) Character values
Answer: d
Clarification: The Number class is used to work with all the number type of values. The integers, float, double, byte etc. are all number type values. Character is not a number value.

11. Which function should be used to exit from the program that is provided by System class?
a) exit(int);
b) gc();
c) terminate();
d) halt();
Answer: a
Clarification: The exit function should be used to terminate the program. The function is passed with an argument. The argument indicated the type of error occurred.

12. Which class contain runFinalization() method?
a) Finalize
b) System
c) Final
d) SystemFinal
Answer: b
Clarification: The runFinalization() Function is defined in the System class. The function is used to finalize an object which undergo destruction. The action is required to terminate the object properly.

13. What does load(String)::= function do, in System class?
a) Loads dynamic library for a path name
b) Loads all the dynamic libraries
c) Loads all the Number in string format
d) Loads the processor with calculations
Answer: a
Clarification: Only the specified path named dynamic libraries are loaded. All the dynamic libraries can’t be loaded at a time. Hence we use this function for specific libraries.

14. Which is not a System class variable?
a) err
b) out
c) in
d) put
Answer: d
Clarification: Put is not a System class variable. The most general and basic variables are err, out and in. The variables can handle most of the tasks performed in a program.

15. Which package contains the utility classes?
a) java.lang
b) java.utility
c) java.util
d) java.io
Answer: c
Clarification: The package java.util contains all the utility classes. This package also contains generic data structures, date, time etc. These can be used in any java program, you just have to include java.util package.

Object Oriented Programming (OOPs) Multiple Choice Questions & Answers (MCQs) on “Classes”.

1. Which of the following is not type of class?
a) Abstract Class
b) Final Class
c) Start Class
d) String Class
Answer: c
Clarification: Only 9 types of classes are provided in general, namely, abstract, final, mutable, wrapper, anonymous, input-output, string, system, network. We may further divide the classes into parent class and subclass if inheritance is used.

2. Class is pass by _______
a) Value
b) Reference
c) Value or Reference, depending on program
d) Copy
Answer: b
Clarification: Classes are pass by reference, and the structures are pass by copy. It doesn’t depend on the program.

3. What is default access specifier for data members or member functions declared within a class without any specifier, in C++?
a) Private
b) Protected
c) Public
d) Depends on compiler
Answer: a
Clarification: The data members and member functions are Private by default in C++ classes, if none of the access specifier is used. It is actually made to increase the privacy of data.

4. Which is most appropriate comment on following class definition?

class Student 
{
    int a; 
    public : float a; 
};

a) Error : same variable name can’t be used twice
b) Error : Public must come first
c) Error : data types are different for same variable
d) It is correct
Answer: a
Clarification: Same variable can’t be defined twice in same scope. Even if the data types are different, variable name must be different. There is no rule like Public member should come first or last.

5. Which is known as a generic class?
a) Abstract class
b) Final class
c) Template class
d) Efficient Code
Answer: c
Clarification: Template classes are known to be generic classes because those can be used for any data type value and the same class can be used for all the variables of different data types.

6. Size of a class is _____________
a) Sum of the size of all the variables declared inside the class
b) Sum of the size of all the variables along with inherited variables in the class
c) Size of the largest size of variable
d) Classes doesn’t have any size
Answer: d
Clarification: Classes doesn’t have any size, actually the size of object of the class can be defined. That is done only when an object is created and its constructor is called.

7. Which class can have member functions without their implementation?
a) Default class
b) String class
c) Template class
d) Abstract class
Answer: d
Clarification: Abstract classes can have member functions with no implementation, where the inheriting subclasses must implement those functions.

8. Which of the following describes a friend class?
a) Friend class can access all the private members of the class, of which it is a friend
b) Friend class can only access protected members of the class, of which it is a friend
c) Friend class don’t have any implementation
d) Friend class can’t access any data member of another class but can use it’s methods
Answer: a
Clarification: A friend class can access all the private members of another class, of which it is a friend. It is a special class provided to use when you need to reuse the data of a class but don’t want that class to have those special functions.

9. What is the scope of a class nested inside another class?
a) Protected scope
b) Private scope
c) Global scope
d) Depends on access specifier and inheritance used
Answer: d
Clarification: It depends on the access specifier and the type of inheritance used with the class, because if the class is inherited then the nested class can be used by subclass too, provided it’s not of private type.

10. Class with main() function can be inherited.
a) True
b) False
Answer: a
Clarification: The class containing main function can be inherited and hence the program can be executed using the derived class names also in java.

11. Which among the following is false, for a member function of a class?
a) All member functions must be defined
b) Member functions can be defined inside or outside the class body
c) Member functions need not be declared inside the class definition
d) Member functions can be made friend to another class using the friend keyword
Answer: c
Clarification: Member functions must be declared inside class body, though the definition can be given outside the class body. There is no way to declare the member functions outside the class.

12. Which syntax for class definition is wrong?
a) class student{ };
b) student class{ };
c) class student{ public: student(int a){ } };
d) class student{ student(int a){} };
Answer: b
Clarification: Keyword class should come first. Class name should come after keyword class. Parameterized constructor definition depends on programmer so it can be left empty also.

13. Which of the following pairs are similar?
a) Class and object
b) Class and structure
c) Structure and object
d) Structure and functions
Answer: b
Clarification: Class and structure are similar to each other. Only major difference is that a structure doesn’t have member functions whereas the class can have both data members and member functions.

14. Which among the following is false for class features?
a) Classes may/may not have both data members and member functions
b) Class definition must be ended with a colon
c) Class can have only member functions with no data members
d) Class is similar to union and structures
Answer: b
Clarification: Class definition must end with a semicolon, not colon. Class can have only member functions in its body with no data members.

15. Instance of which type of class can’t be created?
a) Anonymous class
b) Nested class
c) Parent class
d) Abstract class
Answer: d
Clarification: Instance of abstract class can’t be created as it will not have any constructor of its own, hence while creating an instance of class, it can’t initialize the object members. Actually the class inheriting the abstract class can have its instance because it will have implementation of all members.

Object Oriented Programming (OOPs) Multiple Choice Questions & Answers (MCQs) on “Data Members”.

1. What is the term used to indicate the variable and constants of a class?
a) Data members
b) Variables of class
c) Data characters
d) Constants
Answer: a
Clarification: The variables inside a class are termed data members of the class. It is not a mandatory rule but variables are used to refer to usual variables used in functions or globally. The term is given because the values stored in those variables represent some kind of data related to class.

2. Data members ________________ (C++)
a) Can be initialized with declaration in classes
b) Can be initialized only with help of constructors
c) Can be initialized either in declaration or by constructor
d) Can’t be initialized
Answer: b
Clarification: The data members are not property of class, those are property of the instances of the class. And the memory for the data members are not reserved until a constructor is called. Hence we use constructors for their initialization after the memory is reserved.

3. Which among the following is true for data members?
a) Private data members can be initialized with declaration in class
b) Static members are initialized in constructors
c) Protected data members can be initialized in class directly
d) Static data members are defined outside class, not in constructor
Answer: d
Clarification: Static members are not property of instances of classes. Those are shared by all the object of classes. Hence those are defined outside the constructor, so as to make them common for all the objects.

4. What should be done for data member to be of user defined structure type?
a) The structure must have been defined before class.
b) The structure must have been defined after the class definition
c) The structure must be predefined
d) The structure type data members can’t be used
Answer: a
Clarification: The structure must have been defined prior to its use. If the structure is not defined, then the memory space will not be allocated for its members. This leads to undefined use of new data types.

5. How many data members can a class contain?
a) 27
b) 255
c) 1024
d) As many as required
Answer: d
Clarification: Any class can have as many data members as required. The only restriction that may arise is when there is not enough memory space. This gives flexibility to define a class with best properties possible.

6. How to access data members of a class?
a) Dot operator
b) Arrow operator
c) Dot or arrow as required
d) Dot, arrow or direct call
Answer: c
Clarification: The data members can never be called directly. Dot operator is used to access the members with help of object of class. Arrow is usually used if pointers are used.

7. To create a pointer to a private data member of a class, outside the class, which among the following is correct?
a) Return the address of the private data member using a member function
b) Access the private member using a pointer outside class
c) Declare the member as pointer inside the class
d) Not possible to create pointer to a private member
Answer: a
Clarification: We can call a public member function and return the address of any private data member. Though the pointer being returned must be defined inside class itself. And the returned address can be stored in a pointer.

8. Which among the following is true for use of setter() and getter() function?
a) Considered best for manipulating data values
b) Considered the only proper way to manipulate the values
c) Considered specially for private members manipulation
d) Considered a red flag, and not recommended for large scale use
Answer: d
Clarification: This concept of getter and setter functions is not acceptable if used too much. This is considered to be inappropriate in OOP perspective. Though it is commonly used, it doesn’t work according to OOP concepts at some higher level of understanding.

9. What is the output of following code?

int n=10;		// global
class A()
{
	private : int n;
	public : int m;
	A()
	{ 
		n=100; m=50;
	}
void disp()
{
	cout<<”n”<<m<<n;
};

a) 1050100
b) 1005010
c) n5010
d) n50100
Answer: d
Clarification: In cout we have specified n as a string to be printed. And m is a variable so its value gets printed. And global variable will not be used since local variable have more preference.

10. The static member functions can only use ________
a) Static data members
b) Private data members
c) Protected data members
d) Constant data members
Answer: a
Clarification: The static member functions can only access static data members. This is because the static member function can’t work with the properties that change object to object. It is mandatory that only the common properties of all the objects be used. And only static data members are common to all as those are property of class.

11. A class can have self-referential data members.
a) True
b) False
Answer: b
Clarification: The data members in a class can never refer to own class type. This is not possible because the data members should have some memory allocated for its object before the self-reference is used, but class must call constructor for that. Hence not possible.

12. What is the keyword used to make data members have same value?
a) static
b) const
c) double
d) abstract
Answer: b
Clarification: The keyword const can be used anywhere to make the variable have same value all the time. This restriction is made to use the same value whenever required. Also, this can restrict accidental changes.

13. Which data members can be inherited but are private to a class?
a) Private
b) Protected
c) Protected and Static
d) Privately inherited
Answer: b
Clarification: Static members inheritance also depends on the type of specifier they have. Only the protected members can be inherited but remain private to class. If static members are defined in private access, they won’t be allowed for inheritance.

14. The arguments passed to member functions by reference are considered as data members of class.
a) True
b) False
Answer: b
Clarification: This is a wrong statement. As only the data defined inside class is considered as its member. But even if a variable is passed by reference it would be the same variable that is outside the class. Hence it can’t be considered class member.

15. Which among the following is not allowed for data member declaration?
a) int a;
b) static int a;
c) abstract a;
d) Boolean a;
Answer: c
Clarification: The abstract keyword in the declaration of data members is not allowed. This is because the abstract keyword features can’t be used with the data members of the class. We can have all other syntax given, but not abstract.

Object Oriented Programming (OOPs) Multiple Choice Questions & Answers (MCQs) on “Single Level Inheritance”.

1. Which among the following defines single level inheritance?
a) One base class derives another class
b) One derived class inherits from one base class
c) One base class inherits from one derived class
d) One derived class derives from another derived class
Answer: b
Clarification: If only one base class is used to derive only one subclass, it is known as single level inheritance. The reason of this name is that we inherit the base class to one more level and stop the inheritance any further.

2. If class A and class B are derived from class C and class D, then ________________
a) Those are 2 pairs of single inheritance
b) That is multilevel inheritance
c) Those is enclosing class
d) Those are all independent classes
Answer: a
Clarification: Since class A is derived from class C and then class B is derived from class D, there are two pairs of classes which shows single inheritance. Those two pairs are independent of each other though.

3. If single inheritance is used, program will contain ________________
a) At least 2 classes
b) At most 2 classes
c) Exactly 2 classes
d) At most 4 classes
Answer: a
Clarification: The program will contain at least 2 classes in the sense of base and derived classes. At least one base class and one derived class must be there. Types of inheritance remains the same though.

4. Single level inheritance supports _____________ inheritance.
a) Runtime
b) Compile time
c) Multiple inheritance
d) Language independency
Answer: a
Clarification: The runtime inheritance is done when object of a class is created to call a method. At runtime the function is searched if it is in class of object. If not, it will search in its parent classes and hierarchy for that method.

5. Which method in the code below is single level inherited?

class A
{
	protected int a, b;
	public: void show()
	{ 
		cout<<a<<b;
	}
};
class B: public A
{
	public: void disp()
	{ 
		cout<<a++<<b++; 
	}
};
class C: private A, public B
{
	void avg()
	{ 
		cout<<(a+b)/2; 
	}
};

a) Class A
b) Class B
c) Class C
d) None
Answer: b
Clarification: Class B is using single level inheritance. Class C is using multiple inheritance. And class A is parent of other two classes.

6. If single level inheritance is used and an abstract class is created with some undefined functions, can its derived class also skip some definitions?
a) Yes, always possible
b) Yes, possible if only one undefined function
c) No, at least 2 undefined functions must be there
d) No, the derived class must implement those methods
Answer: d
Clarification: The derived class must implement those methods. This is because the parent class is abstract and hence will have some undefined functions which has to be defined in derived classes. Since we are using single level inheritance, if derived class doesn’t implement those functions then one more class has to be there which will become multi-level inheritance.

7. Which among the following is false for single level inheritance?
a) There can be more than 2 classes in program to implement single inheritance
b) There can be exactly 2 classes to implement single inheritance in a program
c) There can be more than 2 independent classes involved in single inheritance
d) The derived class must implement all the abstract method if single inheritance is used
Answer: c
Clarification: If more than 2 independent classes are involved to implement the single level inheritance, it won’t be possible as there must be only one child and one parent class and none other related class.

8. Which concept will result in derived class with more features (consider maximum 3 classes)?
a) Single inheritance
b) Multiple inheritance
c) Multilevel inheritance
d) Hierarchical inheritance
Answer: b
Clarification: If single inheritance is used then only feature of a single class are inherited, and if multilevel inheritance is used, the 2nd class might have use private inheritance. Hence only multiple inheritance can result in derived class with more features. This is not mandatory but in a case if we consider same number of features in each class, it will result the same.

9. Single level inheritance is safer than _____________
a) Multiple inheritance
b) Interfaces
c) Implementations
d) Extensions
Answer: a
Clarification: Interfaces also represent a way of inheritance but is a wide word to decide which inheritance we are talking about in it, hence can’t be considered. Implementation and extensions also doesn’t match that level of specific idea. And multiple inheritance not so safe as it might result in some ambiguity.

10. Which language doesn’t support single level inheritance?
a) Java
b) C++
c) Kotlin
d) All languages support it
Answer: d
Clarification: All the languages support single level inheritance. Since any class can inherit other classes as required, if single level inheritance was not allowed it would result in failing a lot of features of OOP.

11. What is the output of the following program?

class A
{
	protected: int a,b;
	public: void disp()
	{ 
		cout<<a<<b; 
	}
};
class B:public A
{
	int x,y;
};

a) Garbage value
b) Compile time error
c) Runtime error
d) Runs but gives random values as output
Answer: b
Clarification: The compiler doesn’t find the main function and hence will throw an error main() missing. This program is using single level inheritance but the program is incomplete. Every program must implement main function.

12. What is the output of the following program?

class A
{  
	float sal=40000;  
}  
class B extends A
{  
	int salBonus=10000;  
	public static void main(String args[])
	{  
		B p=new B();  
		System.out.println("B salary is:"+p.sal);  
		System.out.println("Bonus of B is:"+p.bonus);  
	}  
}

a)

B salary is: 4000.0
Bonus of B is: 10000

b)

B salary is 10000
Bonus of B is: 4000.0

c) Compile time error
d) Runtime error
Answer: a
Clarification: The program gives output as in option a. The program have used single level inheritance and hence have access to the parent class methods and variables. This program simply prints the value from parent class and from the child class.

13. Single level inheritance will be best for___________
a) Inheriting a class which performs all the calculations
b) Inheriting a class which can print all the calculation results
c) Inheriting a class which can perform and print all calculations
d) Inheriting all the classes for different calculations
Answer: b
Clarification: Inheriting a class which can perform the most common task will be more efficient. If class which can perform all the calculations is inherited then there won’t be any problem to print the result too. But if a class which can do the most common task for all the other tasks, it will make real use of inheritance.

14. Which constructor will be called first from the classes involved in single inheritance from object of derived class?
a) Base class constructor
b) Derived class constructor
c) Both class constructors at a time
d) Runtime error
Answer: a
Clarification: The base class constructor will be called first from the object of derived class constructor. When the derived class members are to be initialized and allocated memory, the base class members should also be confirmed with the memory allocation.

15. If base class contains 2 nested classes, will it be possible to implement single level inheritance?
a) Yes, always
b) Yes, only if derived class also have nested classes
c) No, it will use more than 2 classes which is wrong
d) No, never
Answer: a
Clarification: The nested classes are also members of a class. They behave as a used defined data type with some methods implementation. So the inheritance will be as usual with the nested classes being member of base class and of derived class if not private.

Object Oriented Programming (OOPs) Multiple Choice Questions & Answers (MCQs) on “Static Data Members”.

1. Which among the following best defines static variables members?
a) Data which is allocated for each object separately
b) Data which is common to all the objects of a class
c) Data which is common to all the classes
d) Data which is common to a specific method
Answer: b
Clarification: The static data members are made common to all the object of a class. They doesn’t change from object to object. Those are property of class rather than of any individual object.

2. Which keyword should be used to declare static variables?
a) static
b) stat
c) common
d) const
Answer: a
Clarification: The keyword used to declare static variables is static. This is must be used while declaring the static variables. The compiler can make variables static if and only if they are mentioned with static keyword.

3. Any changes made to static data member from one member function _____________
a) Is reflected to only the corresponding object
b) Is reflected to all the variables in a program
c) Is reflected to all the objects of that class
d) Is constant to that function only
Answer: c
Clarification: The changes made from any function to static data member will be a common change for all the other objects also. If the change is made with respect to one object and change is printed from another object, the result will be same.

4. Which is the correct syntax for declaring static data member?
a) static mamberName dataType;
b) dataType static memberName;
c) memberName static dataType;
d) static dataType memberName;
Answer: d
Clarification: The syntax must firstly be mentioned with the keyword static. Then the data type of the member followed by the member name should be given. This is general form of declaring static data members.

5. The static data member ______________________
a) Must be defined inside the class
b) Must be defined outside the class
c) Must be defined in main function
d) Must be defined using constructor
Answer: b
Clarification: The static data members must be defined outside the class. Since these are common to all the objects and should be created only once, they must not be defined in the constructor.

6. The syntax for defining the static data members is __________
a) dataType className :: memberName = value;
b) dataType className : memberName = value;
c) dataType className . memberName = value;
d) dataType className -> memberName =value;
Answer: a
Clarification: The syntax doesn’t contain the static keyword. Since it is already been declared as static inside the class. The data type and the corresponding class name must be there to allocate the variable to a class. The value is assigned using scope resolution operator for the member name.

7. If static data members have to be used inside a class, those member functions _______________
a) Must not be static member functions
b) Must not be member functions
c) Must be static member functions
d) Must not be member function of corresponding class
Answer: c
Clarification: Only the static member functions can access the static data members. The definition of static members is made common and hence the member function should be capable of manipulating the static data members.

8. The static data member __________________________
a) Can be accessed directly
b) Can be accessed with any public class name
c) Can be accessed with dot operator
d) Can be accessed using class name if not using static member function
Answer: d
Clarification: The static data members can be accessed using the class name also. If the member functions is not used or is not to be used then we can call the static data members directly by using its corresponding class name.

9. Which among the following is the correct syntax to access static data member without using member function?
a) className -> staticDataMember;
b) className :: staticDataMember;
c) className : staticDataMember;
d) className . staticDataMember;
Answer: b
Clarification: For accessing the static data members without using the static member functions, the class name can be used. The class name followed by scope resolution, indicating that static data members is member of this class, and then the data member name.

10. Which data members among the following are static by default?
a) extern
b) integer
c) const
d) void
Answer: c
Clarification: The const data members of any class are made static by default. This is an implicit meaning given by the compiler to the member. Since const values won’t change from object to object, hence are made static instead.

11. What is the output of the following program?

class Test
{
	private:	static int x;
	public: static void fun()
	{
		cout << ++x << “ ”;
	}
};
int Test :: x =20;
void main()
{
	Test x;
	x.fun();
	x.fun();
}

a) 20 22
b) 20 21
c) 21 22
d) 22 23
Answer: c
Clarification: The static member is initialized with 20. Then the function is called which used pre-increment and printed value of x. The function is called twice. Hence we get 21 22 as output.

12. Whenever any static data member is declared in a class ______________________
a) Only one copy of the data is created
b) New copy for each object is created
c) New memory location is allocated with each object
d) Only one object uses the static data
Answer: a
Clarification: The static data is same for all the objects. Instead of creating the same data each time an object is created, the compiler created only one data which is accessed by all the objects of the class. This saves memory and reduces redundancy.

13. If object of class are created, then the static data members can be accessed ____________
a) Using dot operator
b) Using arrow operator
c) Using colon
d) Using dot or arrow operator
Answer: d
Clarification: The static data members can be accessed in usual way as other members are accessed using the objects. The dot operator is used generally. Arrow can be used with the pointers.

14. What will be the output of the following program?

class Test
{
	public: Test() 
	{ 
		cout  << "Test's Constructor is Called " << endl;  
	}
};
 
class Result
{
	static Test a;
	public:
	Result() 
	{ 
		cout  << "Result's Constructor is Called " << endl; 
	}
}; 
 
void main() 
{ 
	Result b; 
}

a) Test’s Constructor is Called
b) Result’s Constructor is Called
c) Result’s Constructor Called Test’s Constructor is Called
d) Test’s Constructor Called Result’s Constructor is Called
Answer: b
Clarification: The output is the message printed from the constructor of class Result. There is no inheritance used hence only one constructor is called. Since static members are declared once in class declaration and are not defined. The constructor of class Test will not be called.

15. Which among the following is wrong syntax related to static data members?
a) className :: staticDataMember;
b) dataType className :: memberName =value;
c) static dataType memberName;
d) className : dataType -> memberName;
Answer: d
Clarification: The syntax given in option d doesn’t belong to any particular declaration or definition. First one is to access the static members using the class name. Second is to define the static data outside the class. Third syntax id to declare a data member as static in a class.

Object Oriented Programming (OOPs) Multiple Choice Questions & Answers (MCQs) on “IO Class”.

1. What is the use of IO class?
a) To handle all the input operations
b) To handle all the output operations
c) To handle all the input and output operations
d) To handle all the input and output to the standard input
Answer: c
Clarification: The IO class provides functions that can be used to handle input and output operations. All the inputs from standard input and standard output, and also from the files can be handled. This gives the flexibility to make the programs more user friendly.

2. IO class provides input and output through ______________________
a) Data streams
b) Serialization
c) File system
d) Data streams, serialization and file system
Answer: d
Clarification: The IO classes are made such that those can support the input and output from any type of source or destination. The input can be taken from system file and standard input and also some special devices if conned. Same is case to show the output.

3. Which among the following class contains the methods to access character based console device?
a) Console
b) File
c) Device
d) Pipe
Answer: a
Clarification: The Console class contains the methods to access the character based devices. The devices which can stream the data as character set. All those devices can be made use of by using the methods of class Console.

4. File class is ____________________________
a) An abstract of file representation only
b) An abstract of path names only
c) An abstract which can be used to represent path names or file
d) An abstract which can represent a file in any format
Answer: c
Clarification: The File class is made to operate with the files. The file can be of any type. All the input and output operations that have to be performed on a file can be done using File class object.

5. What is a FileDescriptor?
a) A handle for machine specific structure of an open file
b) A handle for program specific structure of an open file
c) A handle for compiler specific structure of an open file
d) A handle for representing device files structure
Answer: a
Clarification: The machine specific structure of an open file have to be handled in some special ways. FileDescriptor class can handle those files. The FileDescriptor can also handle open socket, another source, sink of bytes.

6. FileInputStream _________________________
a) Gets the input stream from any device file
b) Gets the input stream from any open socket
c) Gets the input stream from any cache
d) Gets the input stream from any open file only
Answer: d
Clarification: The most specific answer is that the FileInputStream can only be used for the opened files. The class can work only for the file type. No socket or another source are allowed to be accessed.

7. What does FilePermission class do?
a) This class is used to give permission rights to a file
b) This class is used to restrict the use of permissions
c) This class is used to represent device access permissions
d) This class is used to represent file access permissions
Answer: d
Clarification: The FilePermission can’t get access to the device access permissions. The Permission is given to a file when it is created or otherwise when a privileged user changes it. Then these permission rights can be accessed using the FilePermission class.

8. Which class among the following makes incorrect assumptions?
a) LineNumberInputStream
b) LineNumberReader
c) LineReader
d) LineBuffer
Answer: a
Clarification: The LineNumberInputStream class makes false assumptions. The false assumption is that it assumes, all the byte data is a character. Which is actually not the case, instead the character have one byte memory space.

9. Reader class is _________________
a) Used to read from files
b) Abstract class to read character streams
c) Abstract class to input character streams
d) Used to take input from standard input stream
Answer: b
Clarification: The Reader class is an abstract class that can be used to read characters stream. It can’t be used for any kind of input. It can just read the existing data.

10. Which class can handle IO class interrupt?
a) ExceptionIO
b) InteruptedIO
c) InteruptedIOException
d) IOInteruptException
Answer: c
Clarification: The only class which handles the IO class interrupts is InteruptedIOException class. This class is specially provided to handle any case that involves the execution interrupt.

11. StringReader handles _____________________
a) Any character stream
b) A character stream whose source is an array
c) A character stream whose source is character array
d) A character stream whose source is String only
Answer: d
Clarification: The StringReader can only work with the string type data. Even if a character array is given, it might produce some errors in code. Hence only the string values can be handled properly.

12. Which exception handler can be used when character encoding is not supported?
a) UnsupportedException
b) UnsupportedEncodingException
c) SupportException
d) EncodingException
Answer: b
Clarification: The encoding that is unsupported in a system can be handled. The exception handler is UnSupportedEncodingException class. An object of this class can be created which will catch the exception and handle it.

13. PushBackReader allows the streams to be pushed back to the stream.
a) True
b) False
Answer: a
Clarification: The PushBackReader allows the character streams handling. The main feature is that the stream can be pushed back to the stream. This is used in special cases of handling input stream.

14. RandomAccessFile can be used to _______________________
a) Read from a random access file
b) Write to a random access file
c) Read and write to a random access file
d) Restricts read and write to a random access file
Answer: c
Clarification: The RandomAccessFile class instance can be created to handle input and output operations to a random access file. It first checks the permissions on the file and then any required operation can be done on a random access file. Comparatively faster than other files access.

15. Which among the following is a serialization descriptor for any class?
a) StreamClass
b) ObjectStreamClass
c) ObjectStream
d) StreamObjectClass
Answer: b
Clarification: The ObjectStreamClass object can be created to handle serializations. The class is provided specially for the serializations. It is descriptor like we have a file descriptor to handle/access files.