Top Java Programming Interview Questions and Answers

Java is a popular programming language that allows developers to create complex and fool-proof programs. If you are a developer attending a programming and technical interview, you will be asked Java programming interview questions at various stages of your interview, regardless of the company you are applying to. To assess your knowledge of the language, FAANG, and tier-1 companies ask core Java programming interview questions about writing code and programming theory. Given that Java is one of the most widely used programming languages globally, practicing responses to common Java interview questions is essential for advancing in competitive technical interviews.

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Let's take a look at some of the most common Java programming interview questions and answers for freshers and experienced developers that are asked in technical interviews at FAANG and tier-1 companies.

Here’s what we’ll discuss in this article:

• Top 10 Java Programming Interview Questions and Answers
• Sample Java Programming Interview Questions
• FAQs on Java Programming Interview Questions and Answers

Top 10 Java Programming Interview Questions and Answers

In this section, we’ll look at the most popular Java Programming interview questions and answers.

Q1. Is Java a complete Object-Oriented Programming language?

While Java is classified as an Object-Oriented Programming Language, it isn’t 100% Object-Oriented because it uses eight primitive data types which aren’t objects. The eight primitive data types include - boolean, double, long, short, float, char, int, and byte.

Q2. What do you understand about Wrapper Classes in the Java language?

Wrapper classes in Java are essentially used to convert primitive data types into objects in the OOP model. Wrapper classes wrap these primitive data types, a total of 8 in number, into objects of the particular class.

Q3. What do you understand about constructors in Java? What are the types of constructors in Java?

This is one of the most common Java programming interview questions asked in technical interviews. Constructors in Java are blocks of code that are used to initialize objects in a class. Constructors in Java are required to have the same name of the class to initialize objects. The two types of constructors in Java are Default Constructors and Parameterized Constructors.

Q4. What are the main uses of the Super keyword in Java?

In Java, super keywords have the following important functions:

• They are used to call the constructor of the parent class
• They’re used to call methods of the immediate parent class
• They’re used to point to an instance of the variable in the immediate parent class.
  

Q5. Why doesn’t Java make use of Pointers?

Using Pointers generally increases the program’s complexity. Java is a language that maintains the simplicity of code. More so, the Java Virtual Machine implicitly allocates memory to prevent direct access of memory by the user, averting the need for pointers.

Q6. What do you understand about JIT in Java?

This is one of the most common Java programming interview questions asked in technical interviews. JIT, short for Just In Time, is a compiler that converts Java Bytecode into instructions for the processor. The JIT compiler in Java is activated the moment a method is invoked.

Q7. What do you understand about Access Modifiers/Specifiers in Java?

Access Modifiers/Specifiers are special keywords used to protect the information within a class. These keywords restrict access to data members, methods, and constructors in a class. The four different types of Access Specifiers in Java are:

• Public
• Private
• Protected
• Default

Q8. Which are the main OOPs concepts that the Java language exhibits?

The main OOPs concepts that the Java language exhibits are:

• Polymorphism
• Inheritance
• Abstraction
• Encapsulation
  

Q9. What do you understand about Reflection in Java?

Reflection in Java is fundamentally a Runtime API that helps track changes in the behavior of Classes and Objects contained within the Class, methods, and interfaces. With Reflection, programmers can analyze the behavior of various elements at Runtime without requiring to know whether they’ve been called at compile time.

Q10. What do you understand about the Java String Pool?

The Java String Pool is a collection of Strings stored in the heap memory. The String Pool checks whether a certain new object is already present when it is created. If the Object is present in the pool, the reference is accordingly returned to the variable. Else, a new object is created in the heap memory, and the appropriate reference is returned.

Take a look at some Java Interview Questions for Software Developers with five years of experience.

Sample Java Programming Interview Questions for Practice

In this section, we’ll look at some additional Java programming interview questions that you can practice for your upcoming software developer interview.

Java OOPS Concepts Interview Questions

Let’s look at some Java OOPS Concepts interview questions:

1. What is Inheritance in Java?
2. Explain the Data Binding Feature in Java
3. What do you understand about Polymorphism in Java?
4. Differentiate between Runtime and Compile TIme Polymorphism
5. What do you understand about Encapsulation in Java?
6. What do you understand about Dynamic Method Dispatch in Java?
7. Explain the differences between Abstract Classes and Interfaces in Java.
8. What are the different types of Inheritance in Java?
9. Explain Method Overloading and Method Overriding in Java with a examples
10. What is Association in Java?
11. Explain the concept of Object Cloning in java
12. Explain Constructor Overloading in Java?
13. What do you understand about the Multithreading feature in Java?
14. What is the Marker Interface in Java?
15. What are some differences between Post and Get methods in Java?

Take a look at some of the most commonly asked Core Java Interview Questions here.

Advanced Java Programming Interview Questions

In this section, we’ll look at some advanced Java programming interview questions that often appear in technical interviews.

1. What do you understand about inter-thread communication in Java?
2. What are the advantages of Multithreading in Java?
3. Which are the different states in a thread lifecycle?
4. How is thready-safety achieved in Object-Oriented Programming?
5. What are Daemon threads in Java?
6. What do you understand about Atomic Action in Java?
7. What is Thread Pooling and ThreadScheduler in Java?
8. What do you understand about the Copy Constructor in Java?
9. What is the function of the finalize() method in Java?
10. What do you understand about Tokens in Java?
    

These basic and advanced Java Programming interview questions and answers will help you gear up for your upcoming software engineering interview.

Check some Java Multithreading Interview Questions here.

FAQs in Java Programming Interview Questions

Q1. What are the important Java programming concepts that feature in technical interviews?

Some important concepts around which Java programming interview questions are asked include - polymorphism, data binding, abstraction, encapsulation, methods, constructors, multithreading, functions, access specifiers, and classes.

Q2. Are Java programming interview questions asked at Systems Design interviews?

Yes, especially if you are a backend developer who codes in Java, you can expect questions around core Java programming concepts at Systems design interviews.

Q3. What is Multithreading in Java?

Multithreading is a core Java programming feature that enables multiple threads, essentially sub-processes, to run simultaneously and prevent runtime complications. Multithreading in Java helps to build complex software and programs.

Q4. Which Class is considered as the SuperClass in Java Object-Oriented Programming?

In Java, the Object Class is considered the SuperClass of all classes.

Q5. What coding concepts feature in Java technical interviews at FAANG+ companies?

At FAANG+ technical interviews, you’re asked to solve problems around core data structures and algorithms using Java. The important concepts include - arrays, strings, recursion, hash tables, linked lists, trees, graphs, and dynamic programming.

Gear Up For Your Next Technical Interview

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