Hello, Java explorers!
Today, we’re diving into the world of Java packages. Packages in Java are used to group related classes, interfaces, enumerations, and annotations. They serve two primary purposes: categorizing the classes and controlling access through encapsulation.
1. Using Built-in Packages
Java comes with a rich set of built-in packages, like java.util, java.io, java.math, etc., each serving a different purpose.
Example of using a built-in package:
import java.util.ArrayList;
import java.util.HashMap;
public class Main {
public static void main(String[] args) {
ArrayList list = new ArrayList<>();
HashMap map = new HashMap<>();
// You can use classes from java.util package
}
}
2. Creating Custom Packages
Creating your own packages is a great way to organize your code, especially in larger projects. **Example structure of a project with custom packages:**Project Name src com example myapp MyClass.java utilities UtilityClass.java
How to declare a package in a Java file:- In MyClass.java:
package com.example.myapp;
public class MyClass {
// Class content
}
In UtilityClass.java:
package com.example.utilities;
public class UtilityClass {
// Class content
}
Exercise:
Create a Project with Multiple PackagesYour exercise is to create a Java project that includes:- A main package (e.g., com.myapp).
- At least two subpackages (e.g., com.myapp.models, com.myapp.utilities).
- Multiple classes distributed across these packages, where classes in one package use classes or interfaces from another package.
Conclusion
Well done! You’ve learned about Java packages and their significance in organizing and structuring your Java projects. Using packages efficiently can greatly enhance the maintainability and readability of your code.Try creating a small project with custom packages, experimenting with different structures and hierarchies. This practical experience will solidify your understanding of how packages work in Java.Enjoy coding, and keep exploring the vast possibilities with Java packages!