Top 10 Java Interview Questions and Answers

Java is one of the most influential programming languages ever used for the longest time since several decades. It was developed by James Gosling in the year 1990s. And since then, the world has witnessed 12 distinguishable updated versions of Java. Java has become most in demand in the programming language. It has a large and active developer community, extensive libraries and frameworks, and widespread adoption in various industries. Java has gained a lot of popularity over the years with opening career opportunities in the same field, leading to a lot of people trying to learn and embark on their professional programming journey through Java Certification.

In this blog, we will be talking about Java interview questions and answers which will be helpful and very insightful for you while you prepare for your dream job, which is useful for both freshers and experienced. Let’s get you prepped up so that you can brush up on your concepts and excel in your interview. But before we proceed, don’t forget to bookmark this article so that you can keep it in hand before your interview and avoid the panic-filled situation one faces before their interview. Without any further ado let’s begin.

Here is a compiled list of the Top 10 Java Interview questions with answers which will you stand out in that interview you have been trying your best.

1. What is Java?

Java is a popular and multi-programming language that allows developers to create software applications that can run on various devices and platforms. The rules and syntax of Java are highly based on C++ and C languages. In simple words, Java is a tool or language that developers use to give instructions to computers. One of the greatest key features of Java is that it works on the “write once, run anywhere” feature. If a program is written once in a notebook computer, you can easily change its portability on a mobile device.

2. Why is Java said to be an object-oriented Language?

Java is considered to be an object-oriented language since it adheres to all the principles of encapsulation, inheritance, polymorphism, and abstraction, which are very often referred to as the SOLID Principles of OOPs. Object-oriented programming paradigms revolve around the concept of “objects”, which are instances of classes.

These concepts of an object-oriented programming language often contain data and code that is associated with the functions it is linked with.

3. Mention a few differences between C++ and Java.

C++ is a language that supports procedural, object-oriented, and generic programming. C++ program language runs on the feature of “write once, compile everywhere” and works on manual memory management. Where Java is an object-oriented language. It is highly influenced by C++ and C programming languages, with additional features and stricter rules. Java does automatic memory management with the help of garbage collection.

C++ is a programming language which has a standard library, which is said to be relatively smaller than the library of Java.

Java has a large and comprehensively bigger library, it consists of open networks, I.O Operations, and network bases. It has a vast eco-system consisting of third-party libraries and frameworks.

C++ uses exceptions of error handling, developers manually handle the errors by using “try-catch” blocks.Java enforces mandatory exception handling. Exceptions are explicitly declared in the method signature using the “throws” keyword or caught within “try-catch” blocks.

4. Can you share what is JVM?

JVM stands for Java Virtual Management. It is an important component of the Java Platform, which is an essential part of the Java program. The JVM acts as an interpreter between the environment and the Java bytecode.

When a Java program is compiled, it is converted into byte code as a platform-independent representation of the program.

Its infrastructure technically comprises of Classloader, bytecode execution, Just-in-time compilation (JIT), Memory management, and platform independence.

JVM is known for providing cross-platform compatibility and runtime performance for which Java is very known.

5. What is an online Java Compiler?

An online Java compiler is a web-based tool, which helps developers to write, compile, and execute code without having to install a Java development application. It provides an interactive coding environment for the developers, to experiment, develop code and learn the language.

Online Java compiler includes features such as code editor, compilation, execution, error reporting, shareability, and integration of the learning resources.

6. Can you explain what is JDK?

JDK stands for Java Development Kit. The software development kit is provided by Oracle Corporation for developing Java applications. The JDK includes the necessary tools to compile, execute, develop, and run Java programs.

The few key components of the JDK are Java Compiler, Java Runtime Environment (JRE), Development tools, Libraries and APIs, Documentation, and Examples.

It includes JRE and additional tools for development purposes.

7. What is the difference between ArrayList and LinkedList?

ArrayList	LinkedList
ArrayList internally uses a dynamic array to store elements.	LinkedList uses a doubly linked data structure list to store elements.
ArrayList automatically grows its size when new elements are added by creating a new, larger array and copying the elements.	Insertions and deletions can be performed efficiently by adjusting the references of adjacent nodes.
Array list is faster for sequential access and iterating over elements, as the elements are stored contiguously in memory.	LinkedList takes its overhead time as the elements are transferred between the nodes.
ArrayList consumes more memory as it needs to allocate memory in the underlying array.	LinkedList consumes less memory than ArrayList as the memory is used only for the element and its references.

8. What is Type Casting?

In simple words, firstly, let's break down the meaning of the word Type Casting. Here, type refers to the type of data such as a variable, or an entity and casting means the transfer of data from one variable to another. Type casting is the process of converting a variable type from one to another, either by narrowing or widening the set of use values.

Typecasting is extremely useful when you need to transfer the value of one variable to another or when you are looking to assign a value to a particular variable or when you want to undertake operations on another value.

9. What is Abstraction?

Java's abstraction feature enables you to represent an object or system simply by hiding its intricate implementation details and just exposing the necessary features and behaviors to the outside world. Abstraction is a key notion in object-oriented programming. It helps you to concentrate on an object's function rather than its mechanism.

Abstraction in Java is the act of representing the features without showing in detail the integrity or the explanations.

10. What is Encapsulation?

Encapsulation refers to the technique of hiding the details and properties of the variable. It is in short considered to be the deliverable of abstraction. It operates on the data in a single unit known as a class. It restricts data from outside the class and provides controlled access through methods, ensuring data integrity and hiding implementation details.

It prevents any other data outside the unit to interfere, alter or access the properties or methods encapsulated object.

Conclusion

Here will be ending our Top 10 Java interview questions and answers. I hope you found this blog to the most of your benefit. But if you are intrigued enough to learn better about Java in detail and want to upgrade your career development, you can enroll in Itvedant’s IT courses which have proved to be a leading IT Training Institute and have been catering to many dreams. Thank you for your patient reading and sticking to the end. I will be waiting for you with the same enthusiasm at the beginning of my next blog. Wishing you all the very best for your interview.