Advanced Coding & Software Engineering Program

Java Packages – Complete Tutorial

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Last Updated on: 24th Nov 2025 18:04:46 PM

In Java programming, applications grow quickly—from a few classes to hundreds or even thousands of files. In large applications, hundreds of classes exist. If everything is placed in one folder, the project becomes messy, confusing, and hard to maintain.
To solve this problem, Java provides Packages, one of the most powerful organizational features of the language.

 

A Package in Java is like a folder that groups related classes, interfaces, and sub-packages. It helps you structure your project cleanly, avoid name conflicts, and improve code reusability.

 

What is a Package?

A package in Java is a folder/directory used to group related classes, interfaces, and sub-packages.

 

Packages help in:

✔ Organizing code
✔ Avoiding class name conflicts
✔ Improving maintainability
✔ Access control (public, protected, default)
✔ Reusability (importing packages)

 

Types of Packages in Java

Java supports two types of packages:

1. Built-in Packages (Predefined Packages)

Provided by Java.

Examples:

• java.util → Scanner, ArrayList

• java.io → File, InputStream

• java.lang → String, Math, System

• java.awt → GUI components

• java.sql → JDBC

 

2. User-Defined Packages

Created by the programmer.

Example:

package mypackage;

 

Using Built-in Packages (Example)

import java.util.Scanner;

public class InputExample {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        System.out.println("Enter name:");
        String name = sc.nextLine();
        System.out.println("Hello " + name);
    }
}

 

Why Use Packages? (Real-Life Scenario)

Suppose iKeySkills is creating a big Java course platform with:

• User management

• Payment system

• Courses

• Certificates

• Admin panel

 

Each module can be placed in a separate package:

com.ikeyskills.user
com.ikeyskills.payment
com.ikeyskills.courses
com.ikeyskills.admin

This keeps the project clean and maintainable.

 

Creating User-Defined Packages (Step-by-Step Practical)

Follow this easy practical tutorial.

 

Step 1: Create Folder Structure

Create a main folder:

MyProject
└── src
     └── com
          └── ikeyskills
               └── courses
                    └── CourseInfo.java

 

Step 2: Create the Package File

File: CourseInfo.java

package com.ikeyskills.courses;

public class CourseInfo {
    public void display() {
        System.out.println("Java Course: Beginner to Advanced");
    }
}

 

The first line must be package com.ikeyskills.courses;
This tells Java the class belongs to this package.

 

Step 3: Create Another Class in a Different Folder

File: Main.java (outside the package)

MyProject
└── src
     └── Main.java

 

import com.ikeyskills.courses.CourseInfo;

public class Main {
    public static void main(String[] args) {
        CourseInfo c = new CourseInfo();
        c.display();
    }
}

 

Use import to bring the package class into the program.

Or use wildcard: import com.ikeyskills.courses.*; for all classes in package.

 

Step 4: Compile Package Files (IMPORTANT)

Go to the src folder in terminal:

cd MyProject/src

 

Compile the package class:

javac com/ikeyskills/courses/CourseInfo.java

 

Compile Main.java:

javac Main.java

 

Step 5: Run the Program

java Main

Output

Java Course: Beginner to Advanced

 

Creating Sub-Packages (Nested Packages)

Folder structure:

com
└── ikeyskills
      └── payment
             └── gateway
                    └── Razorpay.java

 

File: Razorpay.java

package com.ikeyskills.payment.gateway;

public class Razorpay {
    public void pay() {
        System.out.println("Payment done using Razorpay!");
    }
}

 

Main Class:

import com.ikeyskills.payment.gateway.Razorpay;

public class Main {
    public static void main(String[] args) {
        new Razorpay().pay();
    }
}

 

Access Modifiers in Packages

Access Modifier	Same Class	Same Package	Subclass (Other Package)	Other Package
public	✔	✔	✔	✔
protected	✔	✔	✔	❌ (except through inheritance)
default	✔	✔	❌	❌
private	✔	❌	❌	❌

 

Packages affect access level:

Modifier	Package Access
public	Accessible everywhere
protected	Accessible in same package + other package but only by subclasses
default (no modifier)	Accessible only in same package
private	Inside same class only

 

Using Fully Qualified Name (No import needed)

 

Example 

public class Main {
    public static void main(String[] args) {
        com.ikeyskills.courses.CourseInfo c = new com.ikeyskills.courses.CourseInfo();
        c.display();
    }
}

 

Good when two classes have the same name.

 

Advantages of Packages

Benefit	Explanation
Organized Code	Logical grouping
Avoid Name Collisions	Same class names in different packages
Security	Access control
Reusability	Easier to reuse code
Maintainability	Easier management of large applications

 

Java API Package Summary Table

Package	Use
java.lang	Basic classes
java.util	Collections, Scanner
java.io	File & input/output
java.net	Networking
java.sql	Database
java.awt	GUI
javax.swing	GUI

 

Final Summary

✔ A package is a folder structure used to organize Java classes
✔ Two types: built-in & user-defined
✔ Use import to access classes from another package
✔ Folder names = package names
✔ Helps maintain clean, structured, secure code in large projects

 

Keep practicing — you're doing amazing!

Happy Coding!    

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