OOP MCQ

1. Which of the following is the functionality of ‘Data Abstraction’?

a) Reduce Complexity

b) Binds together code and data

c) Parallelism

d) None of the mentioned

View Answer

Answer: a

Explanation: An essential element of Object Oriented Programming is ‘Data Abstraction’ which means hiding things. Complexity is managed through abstraction.

2. Which of the following mechanisms is/are provided by Object Oriented Language to implement Object Oriented Model?

a) Encapsulation

b) Inheritance

c) Polymorphism

d) All of the mentioned

View Answer

Answer: d

Explanation: None.

3. Which of the these is the functionality of ‘Encapsulation’?

a) Binds together code and data

b) Using single interface for general class of actions.

c) Reduce Complexity

d) All of the mentioned

View Answer

Answer: a

Explanation: ‘Encapsulation’ acts as protective wrapper that prevents code and data from being accessed by other code defined outside the wrapper.

4. What is ‘Basis of Encapsulation’?

a) object

b) class

c) method

d) all of the mentioned

View Answer

Answer: d

Explanation: Encapsulation is the mechanism that binds together code and data it manipulates, and keeps both safe from outside interface and misuse. Class, which contains data members and methods is used to implement Encapsulation.

5. How will a class protect the code inside it?

a) Using Access specifiers

b) Abstraction

c) Use of Inheritance

d) All of the mentioned

View Answer

Answer: a

Explanation: Each method or variable in a class may be marked ‘public’ or ‘private’. They are called Access Specifiers.

6. What is the output of this program?

 class Test {

     int a;

     public int b;

     private int c;

 }

 class AcessTest {

     public static void main(String args[])

     {

         Test ob = new Test();

         ob.a = 10;

         ob.b = 20;

         ob.c = 30;

         System.out.println(" Output :a, b, and c" + ob.a + " " + ob.b + " " + ob.c);

     }

}

a) Compilation error

b) Run time error

c) Output : a, b and c 10 20 30

d) None of the mentioned

View Answer

Answer: a

Explanation: Private members of a class cannot be accessed directly. In the above program, the variable c is a private member of class ‘Test’ and can only be accessed through its methods.

7. Which of the following is a mechanism by which object acquires the properties of another object?

a) Encapsulation

b) Abstraction

c) Inheritance

d) Polymorphism

View Answer

Answer: c

Explanation: ‘Inheritance’ is the mechanism provided by Object Oriented Language, which helps an object to acquire the properties of another object usually child object from parent object.

8. Which of the following supports the concept of hierarchical classification?

a) Polymorphism

b) Encapsulation

c) Abstraction

d) Inheritance

View Answer

Answer: d

Explanation: Use of Hierarchical classification avoids defining the properities of object explicitly at each level which have acquired their properties from higher levels.

9. Which Keyword from the following is used to inherit properties from one class into another?

a) extends

b) subclasses

c) native

d) all of the mentioned

View Answer

Answer: a

Explanation: None.

10. Which of the following concept is often expressed by the phrase, ‘One interface, multiple methods’?

a) Abstraction

b) Polymorphism

c) Inheritance

d) Encapsulation

View Answer

Answer: b

Explanation: None.

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1. Which of these is a valid keyword in Java?

a) interface

b) string

c) float

d) unsigned

View Answer

Answer: a

Explanation: “String” and “Float” are class types in Java. “unsigned” is a keyword used in C/C++ but not in Java.

2. Which of these is a reserved word in Java Programming Language?

a) method

b) native

c) subclasses

d) reference

View Answer

Answer: b

Explanation: “native” is a valid keyword used to modify method declaration. The valid keyword used in Java language for subclassing is “extends” not subclasses.

3. How many reserved keywords are there in Java language?

a) 50

b) 52

c) 49

d) 45

View Answer

Answer: a

Explanation: As of Java 1.5 there are 50 keywords out of which 48 are used(const and goto keywords are unusable keywords).

4. Which of the following is a Literal Representation?

a) 100

b) ‘100’

c) Sample

d) None of the mentioned

View Answer

Answer: a

Explanation: A constant value in Java is created by using a ‘Literal Representation’ of it. Integer Literals are not enclosed in quotes where as String Literals are enclosed in quotes.

5. What are the types of comments defined by Java?

a) Single-line comment

b) Multi-line comment

c) Documentation comment

d) All of the mentioned

View Answer

Answer: d

Explanation: None.

6. Which of the following is readable by both Computer and Human?

a) Single-line comment

b) Multi-line comment

c) Documentation comment

d) All of the mentioned

View Answer

Answer: c

Explanation: Documentation comment is used to produce an HTML file that documents the given program.

7. Which of the following ‘Seperator’ is most commonly used in Java program?

a) Parenthesis

b) Braces

c) Comma

d) Semicolon

View Answer

Answer: d

Explanation: Semicolon is most commonly used in Java program, which terminates statements.

8. Which of the following is used to name class, method and variables?

a) Identifiers

b) Keywords

c) Both

d) None of the mentioned

View Answer

Answer: a

Explanation: Identifiers are used to name classes, methods and variables.

9. ‘Whitespace’ in Java language may be?

a) A space

b) A new line

c) A tab

d) All of the mentioned

View Answer

Answer: d

Explanation: None.

10. Which of the following is the output of the program?

class Test {

    public static void main(String args[])

    {

        int num = 10;

        System.out.println("The value of num is" +NUM);

    }

}

a) Compilation error

b) Run time error

c) Exception

d) The value of num is 10

View Answer

Answer: a

Explanation: Java is case-sensitive. Identifier which is used to name variable and print are different.

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