Java OOPs interview questions revolve around Object-Oriented Programming, also known as OOPs. It refers to a set of languages in programming that use the concept of objects and classes. Java’s OOPs concepts, such as abstraction, encapsulation, inheritance, and polymorphism, make Java one of the most widely used programming languages in the industry.
Software engineers skilled in Java and OOPs concepts are always in high demand. According to Indeed, Java Developers have the lowest career switch rate of all professions.
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In this article, we will cover:
OOP connects data and functions that operate on them so that no other part of the code can access the data except that function. While most programmers are accustomed to top-down programming, Java OOPs is a step forward in tech democratization because it is built on these pillars. It is critical that you thoroughly understand these OOP features because they are the basis for most Java OOPs interview questions. Let's go over the fundamental Java OOP concepts:
One of the most significant benefits of OOP is that data is hidden from other parts of a language and is placed in a capsule. OOP is involved in encapsulating data by default. Ideally, objects will contain both the data and the methods that affect data. A good OOP practice will mean that you offer getter and setter methods to control data access. Mutable data is protected from being changed and makes application data much safer.
Objects can be created as subtypes of other objects. This is done by inheriting methods and variables from the said objects. This way, objects can support operations defined by anterior types without needing a definition of their own.
Like shape-changing, Java OOP allows one object or method to become a template for another object or method. Single functions can become overloaded, shift shapes and adapt to the related class. Java OOPs have been very successful because the tech industry supports and is supported by OOP.
It displays important information and hides the details of implementation.
Take a look at the most popular back-end development languages you should learn to get a job at FAANG companies.
You need to practice core Java interview questions on OOPs concepts to answer basic Java OOP interview questions. Most Java OOP interview questions will be based on OOP concepts such as encapsulation, polymorphism, inheritance, data abstraction, classes and objects, methods and functions, and exception handling.
Here are a few sample Java OOP interview questions from each category.
1. What is Object-Oriented Programming in Java?
OOP entails real-life entities such as a pencil, television, or a bank account. The basic condition is that this entity should possess a state (for data) and behavior (for method). Using access, specifiers secure access to this data and methods. You can hide data and provide access to specific essentials using encapsulation and data abstraction.
With the help of polymorphism and inheritance, one can reuse code and help overload or override methods. This results in platform-independent applications that are secure and robust.
2. Name some widely used OOP languages.
The most widely used OOP languages are C++, C#, Python, Java, Go, Dart, and Ruby.
3. Is Java purely Object-Oriented?
Java is not entirely an object-oriented programming language. This is because Java still uses primitive data types like float, int, double, char, etc. These data types are stored as stacks and not on the heap. Java also allows static methods to access static variables without using an object.
4. What is Class and Object in Java?
Class is a template used to create objects. It has a state and behavior supported by an Object. This Object is an instance of the said Class. You can think of Class as a human. The state of this human will be factors such as its digestive system, eye color, and age. Its behavior will include things like canEat(), ableToSmell(), and many more.
Your Java OOPs interview prep is incomplete without practicing coding problems. Check out these coding interview questions and answers.
Q1. How much does a Java OOP Developer earn?
A. According to Indeed, the average compensation for a Java Developer is $100,200 per year in the United States, along with a $5,000 bonus per year.
Q2. Is Java developer a good career?
Tech hiring stats dropped initially in 2020 but bounced back quickly by year-end. According to CompTIA, 391,000 new tech positions were added in the US in December 2020. Among these, the largest share of 62,900 postings was for software developers and application developers. As far as job satisfaction is concerned, according to Glassdoor's Best Jobs in America 2021 Survey, Java Developers ranked 1 in the US with a job satisfaction rating of 4.2 out of 5!
Q3. Which companies use Java OOP to build their products?
A. According to Stackshare, 9915 companies, use Java in their tech stacks. Here are the top companies that use Java: Netflix, Uber, Airbnb, Google, Pinterest, Instagram, Spotify, Amazon, Slack, Spring, and more.
Q4. What are the top skills required to become a Java Developer?
A. The top skills in demand these days in a Java Developer are: Software Design and Architecture, Microservices, DevOps Tools, React or Angular, JUnit and Mockito, Design Patterns, Spring Boot, Learn APIs, and JVM Internals.
Q5. What are some Java OOP concept interview questions?
The primary Java OOPs concepts are encapsulation, abstraction, inheritance, and polymorphism. Some of the java interview questions on these concepts are: What is a superclass? What is inheritance? What is hierarchical inheritance? What is polymorphism? What is method overloading? What is encapsulation? What is the difference between public, private, and protected access modifiers? How to achieve data abstraction? What is an exception? What is exception handling?
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