Important Java Interview Questions And Answers

 

Java is the third most trending programming language on the Tiobe Index and ranks in the top 5 languages on Stack Overflow's popular programming language list. It has a thriving community with developers worldwide, offering an excellent platform to learn and improve for any newcomer.

There is a good reason for Java's popularity. When you look at this feature-rich language, it has something to offer to everyone. It has qualities like stability, versatility, architecture-neutrality, ease of learning, and security features, making it a go-to option for many applications.

Java has been a part of almost every domain now, from web development to IoT, Cloud, and machine learning/AI. Its wide usage across industries is a compelling reason it is a most sought-after skill.

Why Are Java Interviews Important?

A Java training in San Francisco can open doors for opportunities in multiple organizations, including the tech giants like Facebook, Google, Netflix, Pinterest, etc. The training will empower you with the right skills and help you with its thoughtful implementation through client-based projects and assignments.

But your journey towards a professional career only starts when you join an organization or start working. Java interviews can be challenging as employers are not only looking at your qualifications and degrees but your skills.

Employers use many tools to evaluate the candidates' tech skills, and the most common of them are technical interviews. These are the most dreaded part for any candidate.

Most students who have been to a reputed Java coding bootcamp get guidance on tackling the interviews. During the career assistance, students are exposed to the common interview questions and tips to answer them.

To help you brush your Java concepts, we have listed the most commonly asked questions by the interviewers during Java interviews. Make sure you go through them to stay confident during your next interview.

Important Java Interview Questions And Answers

1. How is Java different from C++?

Ans: Java coding and C++ are different in many ways. Here are four significant differences.

• Platform independence: Java is platform-independent, but C++ is not. Java works on the concept 'write once, run everywhere' while C++ is based on the concept, 'write once, compile anywhere.'
• Memory management: In C++, memory management is manual, while Java has system-controlled memory management.
• Compiled and interpreted: Java is compiled and interpreted; on the other hand, C++ is compiled.
• Programming Support: C++ supports both procedural programming and object-oriented programming models, while Java supports only object-oriented programming models.

2. Why Do You Call Java Platform Independent?

Ans: Java is called platform independent because it can run on any device with a Java runtime environment (JRE) installed on it. The JRE compiles the code, converting it into bytecode. This bytecode can run on any OS, be it Windows, Linux, or Mac.

3. State the difference between JDK and JRE?

Ans: JDK or Java Development Kit comprises various development tools, including compilers, debuggers, etc. which, aid in the software development. On the other hand, JRE is a bunch of libraries and software supporting the execution of Java programs in JVM.

4. List down the types of memory allocations in Java?

Ans: Java has five significant memory allocations, namely,

• Heap Memory
• Class Memory
• Stack Memory
• Native Method Stack Memory
• Program Counter-Memory

5. Define local variable and instance variable.

Ans: Local Variable: A local variable is defined as a variable whose scope and extent are within the function, method, or block where it is located.

Instance variable: An Instance variable is a non-static variable declared inside the class but outside the scope of any method or block.

6. Mention the various access specifiers for Java classes?

Ans: In Java, access specifiers are the keywords used before a class name defining the access scope. The types of access specifiers for classes are:

• Public: Class, Field, Method is accessible from anywhere.
• Protected: Method, Field is accessible from the same class they are located in, or from the sub-classes, or the class of the same package. They can't be accessed from outside.
• Default: Method, Field, class are accessible from the same package and not from outside of their native package.
• Private: Method, Field is accessible from the similar class to which they belong.

7. Explain data encapsulation.

Ans: Data Encapsulation is an OOP concept where data attributes and their behaviors are bounded as a single unit and kept hidden from the users. It is used to hide data and protect its integrity, preventing unauthorized users from accessing the data.

8. What is a Class in Java?

Ans: A class is defined as a collection of objects that describes the state and behavior of an object. It is like a blueprint or prototype, explaining how the class is created.

9. Define Constructor in Java?

Ans: Constructor in Java coding is a unique method that initializes an object when created. Its name is the same as its class and shares syntactical similarities with the method.

10. What is the difference between the equals() method and equality operator (==) in Java?

equals()	==
It is a method.	It is a binary operator.
Used to compare the two given strings based on their data or content and check the value equality	Used to compare addresses or references and check if both the objects are directed at the same memory location.

11. What are the OOP concepts in Java?

Ans: Object-oriented programming is a fundamental programming method used to design a program consisting of classes and objects. There are four key OOP concepts in Java: abstraction, encapsulation, inheritance, and polymorphism.

12. Why do you use static methods and static variables?

Ans: When you need to share a method or a variable between multiple objects of a class, you can use a static keyword to make them accessible for all objects. This method saves you from creating separate copies for each object.

Conclusion

These were just a few questions to give you an idea about the questions you will face during your interviews. Remember, your basics should be strong, as most questions will be regarding the fundamental Java concepts. It is true for most entry-level positions. So, work on your concepts and the Java coding to land the job of your dreams.