Packages

As Java applications grow, managing classes becomes challenging. Packages solve this problem by organizing related classes into logical groups. They help keep code clean, structured, and easy to maintain.

In real-world Java projects, packages are not optional — they are a fundamental design requirement.

Real-World Understanding of Packages

Think of packages like folders on your computer. You don’t keep all files in one place. Instead, you group them into folders such as Documents, Pictures, and Music.

Java packages work the same way. They group related classes so developers can find, manage, and reuse code easily.

Why Packages Are Important

Packages help Java developers:

• Organize large projects efficiently
• Avoid class name conflicts
• Improve code readability
• Control access using access modifiers

Every professional Java application uses packages extensively.

Types of Packages in Java

Java provides two main types of packages:

• Built-in packages – Provided by Java (for example: java.util)
• User-defined packages – Created by developers

You will work with both types in real applications.

Built-in Packages Example

Java comes with many built-in packages. One of the most commonly used is java.util.

import java.util.Scanner;

public class Main {
    public static void main(String[] args) {

        Scanner sc = new Scanner(System.in);
        System.out.println("Enter your name:");
        String name = sc.nextLine();

        System.out.println("Welcome " + name);
    }
}

Here, the Scanner class comes from the java.util package.

Creating a User-Defined Package

You can create your own package using the package keyword.

package com.dataplexa.utils;

public class Calculator {

    public int add(int a, int b) {
        return a + b;
    }
}

This class now belongs to the com.dataplexa.utils package.

Using a Class from Another Package

To use a class from another package, you must import it.

import com.dataplexa.utils.Calculator;

public class Main {
    public static void main(String[] args) {

        Calculator calc = new Calculator();
        System.out.println(calc.add(10, 20));
    }
}

This keeps code modular and reusable across projects.

Package Naming Conventions

Java follows a standard naming convention for packages:

• Package names are written in lowercase
• They usually follow reverse domain naming
• Example: com.company.project.module

This convention prevents naming conflicts in large systems.

Packages and Access Control

Packages work closely with access modifiers:

• public – accessible everywhere
• protected – accessible within package and subclasses
• default – accessible only within the same package
• private – accessible only within the class

This allows developers to control how classes and methods are exposed.

Packages in Real Applications

Packages are used heavily in:

• Enterprise Java applications
• Frameworks like Spring and Hibernate
• Microservices architectures
• Large team-based projects

They help teams collaborate without code conflicts.

Key Takeaways

• Packages organize Java classes logically
• They prevent naming conflicts
• They improve readability and maintainability
• They are essential for large Java projects

In the next lesson, we will explore access modifiers in detail and see how they control visibility in Java applications.