Hello, Jetto Net followers!

Welcome to our Java Object-Oriented Programming (OOP) series. In the previous article, we learned about creating contracts between classes through interfaces and providing a form of multiple inheritance. In this article, we will explore packages, which make our Java projects more organized, understandable, and manageable.

When learning Java, you'll frequently encounter packages and imports. For beginners, these terms may seem quite unfamiliar, but if your first language was not Java and you have experience with C++ or C#, understanding them will be relatively easier. For those just starting, don't worry; as always, we'll start from the basics.

What is a Package?

In Java, there are numerous classes. Classes are files located within package folders. Logically connected or related classes are placed within the same package. (Those familiar with C++ might relate this to the namespace concept.) The package definition is in the format java.packageName.ClassName.

Import refers to defining a class. If you want to use a class that is not in the same package, you need to import it first. (It is similar to the "using" keyword in C++.) The usage is import java.packageName.ClassName;

Sometimes you might encounter the * symbol instead of a class name. This usage is as follows:
import java.packageName.*; This means you can access all classes in the java.packageName package.

Why Use Packages?

• Avoiding Naming Conflicts: Different developers may create classes with the same name. Packages provide a namespace to prevent such conflicts.
• Organizing Code: Packages help group related classes logically, making the code more organized and understandable.
• Access Control: Packages can be used to control the access of classes and interfaces. For example, you can make a class within a package public to allow classes in other packages to access it.

How to Create a Package?

To create a package, we write the package keyword at the top of the Java file, followed by the package name. The package name is written in a reversed domain name format (e.g., net.jetto.blog).

package net.jetto.blog;
public class Article {
   // ...
}

In the example above, the Article class is within the net.jetto.blog package.

How to Use Packages?

To access a class from another package, we use the import keyword.

import net.jetto.blog.Article;
public class Test {
    public static void main(String[] args) {
        Article article = new Article();
        // ...
    }
}

Here, the Test class uses the Article class from the net.jetto.blog package.

Java's Built-in Packages

The İndirme bağlantısını görmek için Giriş Yap veya Kayıt Ol. website always provides updated definitions of Java packages. Programmers can freely access them. Java is open source, so everyone can access the source programs. On the mentioned site, the API (Application Programmer’s Interface) list includes numerous packages. Each package's classes and interfaces are clearly defined. They are typically sufficient to meet a programmer's needs. Of course, programmers can freely create classes, interfaces, and packages as needed. However, it is often not wise to recreate what is already available in the API. Java APIs contain tested, error-free code, and using them directly saves programmers a lot of time.

For example, the java.lang package contains fundamental classes like String, Math, and System, while the java.util package includes collection classes such as ArrayList and HashMap.

Conclusion

Packages are an important tool in Java that simplifies the management of large projects. By using packages, we can make our code more organized, understandable, and reusable. In our next article, we will continue exploring other important OOP concepts. Feel free to leave your questions or comments in the comments section.

Happy Coding!