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Top 10 Interview Questions for Java Developers

To interview a java developer candidate can be challenging, especially if you’re unfamiliar with the programming language. The goal of the interview is to measure the candidate’s technical background and expertise. You need to assess that they can meet and exceed company expectations for the role.

With that in mind, we provide a list of relevant technical questions and some basic explanations that can help guide you through the interview process.

10 Common Java Developer Interview Questions

Again, you are trying to get a sense for the candidate’s technical knowledge, and how they can apply their expertise to your company’s projects. Below are some questions that will help simplify the interview process.

Can you tell me about JDK and JVM? 

JDK stands for Java Development Kit, and it helps to build and develop Java programs. It consists of the Java Runtime Environment and development tools. The JVM is the Java Virtual Machine. It is a group of software programs which enable the proper execution of newly created programs.

Why is Java considered platform-independent and what does that mean?

Java consists of byte code that works together to allow a software program to perform a larger function. The language can run on any device, no matter the operating system, making it platform-independent.

Why doesn’t Java programming utilize pointers?  

Java is known for its simplicity in code, and pointers add risk factors which increase the complexity of the program. This makes pointers unnecessary and contradictory to Java’s simplicity. Because Java utilizes the JVM for memory allocation, and pointers allow direct access to memory by the user, their use is discouraged.

What is object-oriented programming, and why isn’t Java 100 percent object-oriented?

Object-oriented programming is a model or approach designed around objects, rather than software functions. It revolves around the objects that need to be manipulated, instead of using logical functions. The latter approach can lead to large and complex code that will require regular updates and maintenance.

Java makes use of primitive data types that are not objects, to preserve the language’s simplicity. These types include boolean, byte, char, int, float, double, long and short.

What are Java objects, and how are they created?

An object is an abstract representation with a state, behavior, and identity. It is created by using the new java keyword.

What are wrapper classes in Java, and how are they used?

Primitive data types have dedicated classes. These are called wrapper classes because they “wrap” the primitive data with an object of the same class. The primitive data types are converted into reference types or objects.

What is a constructor and how is it used in Java?

A constructor is used to initialize an object. It is called on when an object is instantiated, and it has no return type. There are two types of constructors: default and parameterized constructors. A default constructor doesn’t use any input variables. The parameterized constructor initializes instance variables when there are provided values, and it takes arguments.

What is the singleton class, and how is it used in Java?

This class is used as a single instance throughout the entire program at any given time in a single JVM. This is accomplished by making the constructor private and providing a unique mechanism to create the class.

Can you explain what the final keyword is?

This is a special keyword used as a non-access modifier. It can be used in three different contexts. The first context is with a variable. When the final keyword is used with a variable, the value cannot be altered once assigned. It can also be used with a method when it can’t be overridden by an inheriting class. And lastly, it can be used with a class declaration, when it’s not being extended by any subclass.

Can you explain what a string pool is in Java?

A string pool is simply a collection of strings (characters) stored in heap memory. The function of the string pool is to check whether an object is already present in the pool or not when it is created. The reference of the variable is returned if it is already present. If not, a new object will be added.

Technology Staffing Firms Can Help

Programming languages are complex. Job interviews surrounding this technology can be tough, not to mention a challenge finding the right candidate in a very competitive talent market. Don’t get so caught up in the technical aspects, that you forget to ask these 5 important questions.

If you’re looking for help pinpointing the right java programmer for your project, you’re not alone. We regularly publish excellent information and resources in our staffing blog to help you identify the best candidates.

We also have an entire staffing process that can help remove all the guesswork for you and your company.

If you need help making sure you find the right candidate contact us today!


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