Java developer Junior job interview FAQ: part 2

In this installment of the series, we continue with the frequently asked questions that you may encounter in the 1st round of job interviews for the position of Junior Java Developer.

See also other articles from the Java developer interview series:

Explain the concept of Java package.

In Java, a package is a way of organizing and grouping related classes, interfaces, resources, and subpackages in one place. Thus, it provides a mechanism for encapsulating and managing code in Java. Using packages can prevent name conflicts between classes with the same name in different packages. Packages also simplify code reuse and sustainability by providing a hierarchical code structure.

What is the role of a method in Java?

In Java, amethod is a function or procedure that is used to perform certain operations. The method is part of the class and defines its behavior. It can accept input parameters, perform operations, and return results. Methods are the basic building blocks of the programme. They allow you to break it down into smaller tasks to achieve better code organization, reusability, and modularity.

Java is also unique for its garbage collection. Explain this principle.

Garbage collection is an automated memory management process in Java that takes care of freeing memory occupied by objects that are no longer available and therefore no longer needed. When we create an object in Java, memory is allocated. However, when an object is no longer available to the program because there is no reference to it, the garbage collector recognizes it and frees the memory, reclaiming it for further use. Java Garbage collection takes care of freeing memory, prevents problems with so called memory leaks and simplifies the life of developers because they do not have to manually manage memory allocation and deallocation.

Interfaces (Java interfaces) are very important in Java. Explain why.

In Java, aninterface is defined as a collection of abstract methods that are used to declare the behavior that classes should implement. Interfaces define what methods should be available in classes, but do not implement them specifically. Classes can implement one or more interfaces, giving them the ability to share and provide common behaviors.

Interfaces are important in Java for several reasons. The first reason is that they allow to achieve abstraction and separation of responsibilities. They help in defining common contracts while separating implementation from declaration.

The second reason is that interfaces allow multiple inheritance of behavior in Java. Classes can implement multiple interfaces, giving them the ability to inherit properties and methods from multiple sources.

The third reason is that interfaces serve as the basis for polymorphism. We can create a variable of the interface type and assign it an instance of the class that implements the interface. In this way, we can work with multiple objects of different classes that implement the same interface and call their methods in a uniform way.

All of these reasons make interfaces an important part of the Java language and ensure flexibility, modularity, and code reusability.

What does the Java Final class expression mean and when is it appropriate to use this feature?

By declaring a class as a final class, we get a class in Java that cannot be inherited from and thus represents a finished, completed class.

The use of the final class can be useful in several of the following cases:

  • To ensure safety: to prevent other classes from inheriting our class and making changes that could affect its behavior or state.
  • Efficiency and optimization: when a class is not intended for inheritance, marking it as final allows the compiler to optimize the class code.
  • Constant classes: in some cases we want to have a class whose objects are immutable and cannot be changed after they are created. Using a final class allows us to achieve this state and ensure that the class objects remain constant.
  • Overriding methods: when a method in a class is marked as final (also. final method), it cannot beoverridden in inheriting classes. This is useful if we want to prevent changes or overrides to certain class methods in inherited classes.

The use therefore depends on the specific scenario and design requirements. In general, marking a class as final is useful if we don’t want it to be inherited or changed, and ensures the stability and safety of our code.

Java beginners often confuse the terms definition and declaration. What is the difference between them?

In general, the difference between adefinition and adeclaration is as follows:

  • A declaration is an entry that informs the compiler of the existence of a variable, method, or class. The type and name of the entity are specified in the declaration, but not all the details or implementation details. The declaration tells the compiler that the entity exists and can be used.
  • While a definition is used to provide the details and implementation of an entity that was previously declared. The definition contains the complete information and implementation of the entity. The definition specifies how the entity should function and exactly what operations it should perform.

To summarize, a declaration informs about the existence of an entity and gives its type and name, while a definition provides the complete information and implementation of the entity.

See more articles for beginner developers: how to become a developer, more about salary of a software developer. Looking for a job as a Java developer? At msg life Slovakia we have great employee benefits. Respond to job offers.

About the author

Jozef Wagner

Java Developer Senior

Viac ako 10 rokov programujem v Jave, momentálne pracujem v msg life Slovakia ako Java programátor senior a pomáham zákazníkom implementovať ich požiadavky do poistného softvéru Life Factory. Vo voľnom čase si rád oddýchnem v lese, prípadne si zahrám nejakú dobrú počítačovú hru.

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