Computer Knowledge

Object-Oriented Programming

2,686 Questions

Object-oriented programming questions test core computer science concepts like classes, inheritance, polymorphism, and encapsulation. The focus includes Java program structures, method overloading, and memory allocation for objects. This topic is essential for technical sections in various recruitment tests.

Java class definitionsMethod overriding rulesPolymorphism conceptsGeneric type parametersMemory allocation in objects

Object-Oriented Programming Questions

Multiple choice

The ability of a language to produce new data types is called

  1. inheritance

  2. reprehensibility

  3. extensibility

  4. encapsulation

  5. abstraction
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

The capability of a programming language to upgrade itself to accommodate new data types which are in new format as per need is called extensibility of that language.

Multiple choice

Which of the following statements is correct?

  1. Class variables have static keyword.

  2. Instance variables are declared within any method.

  3. Local variable is initialised outside the method.

  4. Instance variable can be accessed outside any method.

  5. Local variable is declared outside any method.
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Local variables are defined and initialised inside a method. Instance variables may be declared outside a method and can be accessed only inside that method. Class variables are declared within a class and with static keyword.

Multiple choice

The term black box is associated with

  1. class

  2. object

  3. encapsulation

  4. inheritance

  5. polymorphism
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Encapsulation binds the functions of a program with data. It is a characteristic feature of object oriented programming language. The encapsulated object behaves as if it is a black box.

Multiple choice

Which of the following objects in object-oriented design is a package of software-controlled instruments, which collects data, performs some data processing and transmits this data for further processing?

  1. Weather station

  2. Component design

  3. Map database

  4. Weather data

  5. Interface design
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

 This is a package of software-controlled instruments, which collects data that performs some data processing and transmits this data for further processing.

Multiple choice

Which modifiers may be used with an inner class (non-local), which is a member of an outer class?

Classes use some access specifiers for their accessibilty in other classes or packages.

  1. Public, protected

  2. Only public

  3. Public, protected, private, static, final, or abstract

  4. Only static

  5. Public, private, protected, static but not final
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

All the accessibilties can be given to non-local inner class, which is a member of the outer class. It only gives weaker accessiblilty to non-local inner class, which can be abstract, final, or private(as it is accessible inside outer class).

Multiple choice

class sample9 { public static void main(String []args) { sample s=new sample(); s.walk(); s.fly(); } } class CannotFlyException extends Exception { } interface Bird { public abstract void fly() throws CannotFlyException; } interface Bipe { public void walk(); } abstract class noFlyer
{ public void fly() { System.out.print("cannot fly" );//LINE A } } class sample extends noFlyer implements Bird, Bipe //LINE B { public void walk() { System.out.print("walk" ); } }

Which of the following options is the output of this program?

  1. Compiler error in line with comment LINE A because fly() does not declare to throw CannotFlyException.

  2. Compiler error in line with comment LINE B because fly() is not defined and hence need to declare it abstract.

  3. It crashes after throwing the exception CannotFlyException.

  4. Walk cannot fly

  5. None of the above
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

To override a method, mentioning exception is not important but if you specify Exception, then the specified exception must be the same or a subclass of the specified exception in the method defined in the super class (or interface).