Top 21 Java Interview Questions and Answers

So, you’ve undergone Java developer classes in Pune and are appearing for your first interview? While wishing you luck, we would also like to help you with some core Java interview questions the interviewer might ask you. So, without wasting much of your time, here are 21 Java interview questions for freshers with answers.

21 Java Interview Questions for Freshers with Answers

During your first technical round, you are likely to be asked the following Java basic interview questions, for which you should stay prepared and answer them confidently.

1. Why is Java a platform-independent language?

Java does not depend on any hardware or software. It is because the compiler compiles the code and converts it into a platform-independent code that you can run on various systems. But to do so, your machine should have a runtime environment (JRE) installed.

2. What are the four principles of OOPS?

They include abstraction, polymorphism, inheritance, and encapsulation. An easier way of remembering them is A-PIE.

3. What is abstraction?

Abstraction refers to representing essential features excluding the background details or explanations.

4. What is polymorphism

Polymorphism is “one-interface, many implementations.” It is the ability of a class to provide various implementations of a method as per the object type passed to the method.

5. What is encapsulation?

It is used to hide the properties and behaviors of an object and allows appropriate external access. It restricts other objects from directly altering or accessing the properties or methods of the object encapsulated.

6. What is inheritance?

Inheritance refers to the process through which the object of one class acquires the properties of the objects of another class. An inherited class is called a superclass. The one that does it is termed a subclass. The inheritance process is done using the keyword extends. Inheritance is commonly done to promote code reuse and use polymorphism.

7. Why is Java, not a pure object-oriented language?

Java supports primary data types – Boolean, char, int, float, byte, double and long. Hence, it is not a pure object-oriented language.

8. In what aspects is Java different from C++?

It is different in four areas which include the following.

• Java programs are machine-independent. But C++ programs can run only on machines in which they’ve been compiled.
• Java is a compiled and interpreted language, whereas C++ is only a compiled one.
• Java doesn’t support Multiple inheritances. But C++ does it. Java doesn’t support it to avoid name ambiguity complexities resulting in the diamond problem.
• C++ allows users to use pointers in the program. But Java doesn’t, as it internally uses pointers.

9. What is Dynamic Binding?

This is another significant of Java developer interview questions and answers for freshers. Here, the answer expected is that binding is the linking of a procedure call to the code to be executed in response to the call. Also termed late binding, dynamic binding means that code concerning a particular procedure is unknown until the call of the time at run-time. It is related to polymorphism and inheritance.

10. What is a ClassLoader?

It is a subsystem of Java Virtual Machine that helps load class files while executing a program. ClassLoader first loads the executable file. Java has Bootstrap, Extension, and Application classloaders.

11. What is method overriding?

Method overriding takes place when a subclass declares a method with the same type of arguments as the one declared by one of its superclasses.

12. What is an Association?

It is defined as a relationship that does not have any ownership over another.

13. How do you describe Object Cloning?

Object Cloning in Java allows recreating an object fully similar to an existing one. Java provides a clone() method to clone an existing object with the same functionality as the original one.

14. What are the consequences of not including a static modifier in the main method signature in Java?

You wouldn’t encounter a compilation error. However, then the program is run and as the JVM cannot map the main method signature, the code shows an error “NoSuchMethodError” at runtime.

15. Is it possible to make the main() thread a daemon thread?

In Java multithreading, the main() threads are always non-daemon threads. One cannot change the nature of the non-daemon thread to the daemon thread.

16. Should you follow a catch block after a try block?

No. It isn’t necessary. A catch block or a finally block should follow the try block. If the chances of exceptions are thick, then you should declare them using the throws clause of the method.

17. What is the final keyword in Java?

It is a predefined word used while declaring values to variables. When a value is declared using the final keyword, then the value of the variable stays constant throughout the program's execution.

18. What do you mean by aggregation?

It is the relationship between two classes described as “whole/part” and “has-a” relationship. It is the most specialized version of an association relationship. It consists of the reference to another class and is said to have the class’s ownership.

19. What is a package in Java?

It is a collective bundle of classes, interfaces, and the required libraries and JAR files.

20. What is an object-oriented paradigm?

This is another of the significant Java-related interview questions for freshers. An object-oriented paradigm is a paradigm based on the concepts of objects. It consists of the date and code – data in the form of fields and regulation in the form of procedures. A striking feature of an object-oriented paradigm is that object’s procedures can access and often modify the data fields on their own.

21. What Memory Allocations are available in Java?

The five memory allocations include Class Memory, Heap Memory, Stack Memory, Program Counter-Memory, and Native Method Stack Memory.

So, that was about the 21 Java interview questions and answers. We sincerely hope this helps you and contributes positively to your preparations for your first interview. We wish you the best of your luck. For aspirants, on the other hand, if you are looking for full stack Java training in Pune or Java developer classes in Pune, choose Fullstack Guru.

We offer a comprehensive full stack Java developer course in Pune and have built a reputation as one of the best Java classes in Pune with placement. Call us at +91 81495 15157 to learn more about our courses and other essential details.