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 general knowledge

OOP

  1. Object-oriented program

  2. Object-oriented programming

  3. Object-orient programming

  4. Option-oriented programming
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

OOP stands for Object-Oriented Programming, a programming paradigm based on objects containing data and code.选项 A is grammatically incomplete,选项 C has incorrect grammar ('Object-orient'), and选项 D ('Option-oriented') is completely wrong.

Multiple choice general knowledge science & technology

using which we can pass variables to the other constructor from the constructor in the same class ?

  1. this

  2. super

  3. this()

  4. super()
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

In Java, this() is used to call one constructor from another constructor in the same class. It must be the first statement in the constructor body. 'this' alone refers to the current object instance, while 'super' and 'super()' are used for parent class references and constructors respectively.

Multiple choice general knowledge math & puzzles

In a Java code there are several number of classes & each classes have several methods in it. If the number of classes is decreased by 2 then each class would have 1 method more to keep the total number of methods the same. How many classes are there in that code?

  1. 8

  2. 6

  3. 5

  4. 4
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Let C be classes and M be methods per class. Total = CM. Also Total = (C-2)(M+1). CM = CM + C - 2M - 2 => C - 2M = 2. For C=8, M=3 (Total 24). If C=6, M=4 (Total 24). This fits the condition.

Multiple choice general knowledge math & puzzles

This Design Pattern decouples an abstraction from its implementation so that the two can vary independently.

  1. Adapter

  2. Bridge

  3. Composite

  4. Strategy
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The Bridge pattern is specifically designed to decouple an abstraction from its implementation, allowing both to vary independently. This is useful when you want to avoid a permanent binding between an abstraction and its implementation. Adapter converts interfaces, Composite composes objects into tree structures, and Strategy defines interchangeable algorithms.

Multiple choice general knowledge

interface Image { void displayImage(); } //on System A class RealImage implements Image { private String filename; public RealImage(String filename) { this.filename = filename; loadImageFromDisk(); } private void loadImageFromDisk() { System.out.println("Loading " + filename); } public void displayImage() { System.out.println("Displaying " + filename); } } //on System B class Image2 implements Image { private String filename; private RealImage image; public Image2(String filename) { this.filename = filename; } public void displayImage() { if (image == null) { image = new RealImage(filename); } image.displayImage(); } } class Example2 { public static void main(String[] args) { Image image1 = new Image2("HiRes_10MB_Photo1"); Image image3 = new Image2("HiRes_10MB_Photo2"); image1.displayImage(); // loading necessary image3.displayImage(); // loading necessary image1.displayImage(); // loading unnecessary } } Which design pattern does this code indicate?

  1. Memento

  2. Command

  3. Builder

  4. Proxy
Reveal answer Fill a bubble to check yourself
D Correct answer
Multiple choice softskills creativity

Wrapper class of boolean??

  1. boolean

  2. Boollean

  3. Bolean

  4. Boolean
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Boolean is the correct wrapper class name for the primitive boolean in Java. Option A is the primitive type (not wrapper), while options B and C are misspelled. Java wrapper classes follow specific capitalization rules.

Multiple choice softskills creativity

We don't have the concept of multiple inheritance in Java but we still requires it How does JAVA helps us in this situation?

  1. Import new package

  2. use concrete class

  3. Use of Interfaces

  4. Use Inheritance
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Java does not support multiple inheritance of classes to avoid complexity and the 'diamond problem'. However, it allows a class to implement multiple interfaces, effectively providing a way to achieve the benefits of multiple inheritance.

Multiple choice softskills creativity

which of them are executed before contructor is called??

  1. static variable

  2. Abstract method

  3. Initializer Block

  4. Instance variables
Reveal answer Fill a bubble to check yourself
A,C Correct answer
Explanation

In Java, static variables are initialized when the class is loaded, and initializer blocks (both static and instance) run before the constructor body. Static blocks run once at load time; instance blocks run every time an object is created, just before the constructor.

Multiple choice softskills creativity

Which of them are Not inheritable??

  1. constructor

  2. public instance variable

  3. protected members

  4. Primitive elements
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Constructors are not inherited in Java - each class must have its own constructors. When a subclass is instantiated, it calls the superclass constructor (implicitly or explicitly via super()), but it does not inherit the constructor itself. Public instance variables, protected members, and primitive elements are all inherited by subclasses.

Multiple choice technology programming languages

When a method is overridden, the overriding method can throw only the same exceptions as the overridden method, a subset of them or subclasses of the exceptions.

  1. True

  2. False
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

When overriding a method, the overriding method cannot throw broader (checked) exceptions than the overridden method. It can throw the same exceptions, a subset, or subclasses of those exceptions, maintaining the contract established by the parent method.