CAREER & HIRING ADVICE

Thinking of starting a career in Java development? You’ve made a smart choice!

Even though it’s been around for years, Java remains a popular language finding new areas of application. From a strong community to adaptability, Java is one of the best languages that you could learn as a programmer.

Oh, and if that’s not enough motivation, the average salary of a Java developer currently stands at $100,302 per year.

Now that you’re probably even more pumped to get a new (or your first!) job as a Java developer, you should test your skills and see how well you can answer some of the most common Java interview questions. This way, you can find out which areas you need to brush up on to ace your interview.

So, without further ado, let’s get right into the questions!

Basic Java Interview Questions for Refreshers

In this section, we’ll cover beginner-level questions for those who are just starting off with their career in Java programming.

Question 1: What do you understand about Java?

Java is a fast, high-level, and powerful object-oriented language that was developed in the 1990s. It can be widely used including such domains as game and application development.

Question 2: What is the difference between Java and Python?

Javais statistically typed and compiled whereas Python is dynamically typed. As a result, bugs can be identified and removed from Java more easily.

Question 3: What are the major features of Java?

Java is an object-oriented language which means that it involves classes and methods which define how an object will exist and interact with other elements.

It’s also platform-independent which means that the same code can be used on a number of platforms including Linux, Windows, Mac etc.

Since the language is also interpreted, an Interpreter reads bytecodes and executes them.

Another notable feature is strong memory-management and garbage collection which prevent memory from being used longer than it needs to.

Question 4: What is an object in Java?

Java objects consist of classes and methods that define how these objects will behave.

Question 5: What is the difference between StringBuilder and StringBuffer?

• StringBuffer is synchronized meaning that it’s only possible to call it by one thread at a time, making it less efficient.
• StringBuilder is not synchronized which means that it can be called by multiple threads simultaneously.

Question 6: Differentiate between JDK, JRE, and JVM.

• JVM is a virtual machine that is set up to allow Java apps to run on any platform.
• JRE is a packaged collection of libraries and classes that allow Java programs to run.
• JDK is platform-dependent and comprises development and debugging tools.

Question 7: Define inheritance

Inheritance is a mechanism through which a class can acquire the fields and methods of its parent class. It is only possible in situations where an “is-a” relationship exists between classes.

Question 8: What is the difference between overloading and overriding?

If two methods in the same class have the same name but different parameters, it’s called overloading.

If a method has the same name and parameters in both the parent and child class, it’s called overriding.

Question 9: What is a class in Java?

A class can be defined as the blueprint for objects with similar properties.

Question 10: Explain the creation of a thread-safe singleton in Java using double-checked locking.

This method ensures that the critical block of singleton instance code is locked, making the code more efficient.

Note: As a novice developer, if you learn Java online on codegym.cc, you can better prepare for these and more advanced questions as the platform facilitates hands-on experience.

Intermediate Level Java Interview Questions

Here are a few questions that you might be asked if you already have some experience with Java programming.

Question 1: What is JDK? Mention the variants of JDK?

JDK stands for Java Development Kit and comprises JRE and development tools that are used to create Java applications. A few different variants include:

• Standard Edition
• Enterprise Edition
• Micro Edition

Question 2: What are Access Specifiers in Java?

Access specifiers define how classes and methods can be viewed and used in Java. There are four types of access specifiers namely public, private, protected, and default.

Question 3: Can a constructor return a value?

Constructors return the reference of an object. Once you expect constructors to return a value in addition to this reference, they become a regular method.

Question 4: Explain the keyword “this.”

It’s used to refer to the current object of a method or to invoke a constructor.

Question 5: Explain the keyword “super.”