The pressure to perform well in an interview can feel overwhelming. Despite your knowledge and experience, nervousness could get in the way of putting your best foot forward. But, if you know the questions to expect and how to answer them, you can relax and focus on showcasing what you know and what you can do.
To help you prepare, we've compiled this list of common Java interview questions. We'll explore a few questions for beginner, intermediate, and experienced Java developers, explain how to answer them, and show you what additional steps you can take to nail your interviews.
Beginner Java interview questions
Beginner Java interview questions are designed to test your knowledge of basic Java principles and methods. Here are some common questions and their answers.
What makes Java different from some other programming languages?
- Platform independent
What is "inheritance" in Java?
Inheritance is a core principle in object-oriented programming. It allows an object to inherit the properties of a different class. The class the properties are inherited from is known as the superclass, and the one that inherits the properties is the subclass.
What are the foundational principles related to object-oriented programming?
Intermediate Java interview questions
Intermediate Java interview questions are meant to see if you both understand and know how to apply some of the essential Java principles and tools. Below are some of the more common mid-level Java interview questions.
Describe the Spring framework
The Spring framework is used to make enterprise applications using Java. Its central features can work with essentially any Java application.
Spring is an application framework and container that facilitates the inversion of control (IoC). With inversion of control, a generic network sends the flow of control to customized portions of a program.
How does session management work within servlets?
A session includes the exchange of information between the server and client. These conversations can be managed using:
- Cookie applications
- A session management application programming interface (API)
- Session IDs included in the discourse between the server and the client
- URL rewriting and HTML hidden fields
How is the JDBC ResultSet Interface used?
The ResultSet Interface is used to represent a row in a table. You can also use it to change the cursor and process information from a database.
Experienced Java interview questions
Experienced Java interview questions assess your knowledge of the language's inner workings and advanced features. Here are some common questions you may get asked if the position requires a more experienced Java programmer.
How are "= =" and "equals ()" different?
"==" is the equality operator, and you use it to compare objects and primitives. On the other hand, "equals ()" checks whether two objects are equal within the business logic process.
How does garbage collection work in Java?
Garbage collection is used when an object is either not being referenced or isn't being used. At that point, garbage collection can automatically destroy the object.
Describe what makes a queue and a stack different
A stack is based on the principle of Last In, First Out (LIFO). A queue is different in that it's based on the First In, First Out (FIFO) principle.
What is the base class of all exception classes in Java?
The base class of all exception classes is Java.lang.Throwable. This being the base class means that all exception classes are derived from it.
What are the differences between the static and non-static methods?
With the static method, the static keyword has to precede the method name, and you call it using the class, as in "className.methodName." Also, you can't access any non-static methods or instance variables with the static method.
The non-static method doesn't require you to use a static keyword before the method name, and you can call it as you would any general method. And, the non-static method can access any other static method and variable without the need to rate an instance of the class.
Describe constructor chaining
Constructor chaining in Java involves calling a constructor from another in connection with the current object. To make this happen, a subclass constructor has to be able to invoke its constructor first.
The constructor chaining process can be accomplished either within the same class using "this()" or from the base class by using "super()."
What is referred to by the term "classloader"?
ClassLoader is a subset of Java Virtual Machine (JVM), and it loads class files. When a Java program gets executed, the ClassLoader is what loads it.
Java provides you with three different classloaders:
- Extension ClassLoader
- Bootstrap ClassLoader
- System/Application ClassLoader
Refreshing your knowledge and next steps
The questions above provide a solid foundation for your upcoming interviews, but if you're still feeling unprepared, there are several steps you can take. We offer a wide range of Java courses you can use to refresh your knowledge of the language's features and take your skills to the next level. Java is one of the most widely used and versatile languages, and you can learn how to use it with courses and Skill Paths like:
- Learn Java
- Build Basic Android Apps with Java
- Pass the technical Interview with Java
- Create REST APIs with Spring and Java
Plus, with our Skill Paths, you'll also get the chance to build an impressive portfolio that you can use to showcase your Java skills.
As you learn with us, you'll connect and interact with other developers and discover new ways to use Java. Equipped with the knowledge, experience, and projects you'll gain in your courses, you can impress your interviewer and clearly illustrate your value to the organization. To get started, you can sign up with us today, free of charge.