Packages organize related classes, interfaces and sub-packages into a structured namespace. They prevent naming conflicts and promote code reusability.

Definition List

• Package: A namespace that groups related classes, interfaces and sub-packages together.
• Built-in Package: A package provided by Java's standard library.
• User-Defined Package: A package created by programmers to organize their own classes.
• Import Statement: A statement used to access classes from another package.
• Namespace: A container that helps avoid naming conflicts between classes.

Types of Packages in Java

• Built-in Packages
• User-Defined Packages

Common Built-in Packages

• java.lang — Core Java classes
• java.util — Utility classes and collections
• java.io — Input and output operations
• java.net — Networking classes
• java.awt — GUI components
• javax.swing — Advanced GUI development
• java.sql — Database connectivity
• java.applet — Applet development

Import Syntax

// Import a specific class
import package.name.ClassName;

// Import all classes in a package
import package.name.*;

// Examples
import java.util.*;
import java.applet.Applet;

How to Create a User-Defined Package

1. Create a folder with the desired package name.
2. Create a Java file inside the folder.
3. Declare the package at the top of the file.
4. Save the file using the public class name.

Example 01: Creating a User-Defined Package

package pack1;

public class Demo {
    public void show() {
        System.out.println("Package called");
    }
}

Using a User-Defined Package

import pack1.*;

class A {
    public static void main(String args[]) {
        Demo d = new Demo();
        d.show();
    }
}

Output

Package called

Best Practices

• Use meaningful lowercase package names.
• Follow naming conventions: com.company.project
• Group classes with similar functionality.
• Import only required classes when possible.

FAQ

1. What is a package in Java?

A collection of related classes, interfaces and sub-packages.

2. Why are packages used in Java?

To organize code, improve reusability, prevent naming conflicts and control access.

3. What is the difference between built-in and user-defined packages?

Built-in packages come with Java. User-defined packages are created by programmers.