Java programmer expert
Java Developer Junior job interview FAQ: part 2
In this instalment of the series, we continue with the most frequently asked questions you may encounter in the first round of interviews for the position of Java Developer Junior.
In the article you will learn:
- Explain the concept of a Java package.
- What is a method in Java?
- Java is also unique in its garbage collection. Explain this principle.
- Java interfaces are very important in Java. Explain why.
- What is the Java final class expression and when is it appropriate to use it?
- Java beginners often confuse the terms definition and declaration. What is the difference?
See also other articles in the Java Developer Interview series:
- Java Developer Junior interview part 1
- Java Developer Junior interview part 3
- Java Developer Junior interview part 4
Explain the concept of a Java package.
In Java, a package is a way of organizing and grouping related classes, interfaces, resources, and subpackages in one place. It provides a mechanism for encapsulating and managing code in Java. Using packages can prevent naming conflicts between classes with the same name in different packages. Packages also facilitate code reuse and sustainability by providing a hierarchical code structure.
What is a method in Java?
In Java, a method is a function or procedure that is used to perform certain operations. The method is part of the class and defines its behaviour. It can take input parameters, perform operations and return results. Methods are the basic building blocks of a program. They allow you to break it down into smaller tasks to achieve better code organization, reusability, and modularity.
Java is also unique in its garbage collection. Explain this principle.
Java is also unique in its garbage collection. Explain this principle. Garbage collection is an automated memory management process in Java that takes care of freeing up memory occupied by objects that are no longer available and therefore no longer needed. When we create an object in Java, we allocate memory to it. However, when an object is no longer available to the program because there is no reference to it, the garbage collector recognizes this and frees the memory, reclaiming it for further use. Java garbage collection takes care of freeing up memory, preventing memory leak problems and making life easier for developers by eliminating the need to manually manage memory allocation and deallocation.
Java interfaces are very important in Java. Explain why.
In Java, an interface is defined as a collection of abstract methods that are used to declare the behaviour 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 behaviour.
Interfaces are important in Java for several reasons. The first reason is that they allow to achieve abstraction and separation of responsibilities. They help to define common contracts while separating implementation from declaration.
The second reason is that interfaces allow multiple inheritance of behaviour 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 provide the basis for polymorphism. We can create a variable of the interface type and assign it to an instance of the class that implements the interface. In this way, we can work with multiple objects from different classes that implement the same interface and call their methods in a consistent way.
For all these reasons, interfaces are an important part of the Java language, providing flexibility, modularity and code reusability.
What is the Java final class expression and when is it appropriate to use it?
By declaring a class as a final class in Java, we get a class that cannot be inherited, and thus represents a finished, completed class.
Using the final class can be useful in several of the following cases:
- Security: to prevent other classes from inheriting our class and making changes that could affect its behaviour 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 once they have been 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 (final method), it cannot be overridden in inheriting classes. This is useful if we want to prevent certain class methods from being changed or overridden in inherited classes.
Its use therefore depends on the specific scenario and design requirements. In general, marking a class as final is useful when we don’t want it to be inherited or modified, and ensures the stability and security of our code.
Java beginners often confuse the terms definition and declaration. What is the difference?
In general, the difference between a definition and a declaration is as follows:
- A declaration is an entry that informs the compiler of the existence of a variable, method or class. The declaration gives the type and name of the entity, but not all the details or implementation details. The declaration tells the compiler that the entity exists and can be used.
- A definition, on the other hand, is used to provide the details and implementation of an entity that has previously been declared. The definition contains the complete information and implementation of the entity. The definition specifies how the entity should work and exactly what operations it should perform.
To summarize, a declaration tells you that an entity exists and gives its type and name, while a definition gives the complete information and implementation of the entity.
See more articles for beginners: how to become a developer, more about the developer salary. Looking for a Java developer job? At msg life Slovakia we have great employee benefits. Respond to our job offers!
