Java Packages

Java Packages

👉What is a Package in Java?

A package in Java is a namespace that groups related classes, interfaces, and sub-packages. It helps in code organization, reusability, and preventing name conflicts. Java packages also enhance security and access protection by restricting access to specific classes.

👉Types of Java Packages:-

Java provides two main types of packages:

1. Built-in Packages – Provided by Java (e.g., java.util, java.io, java.sql).
2. User-defined Packages – Created by developers to organize custom Java classes.

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👉How to Create a Package in Java?

Follow these simple steps to create a package in Java:

👉Step 1: Define a Package:

Use the package keyword at the beginning of your Java file.

java

package mypackage; // Declaring package  

public class MyClass {  
    public void showMessage() {  
        System.out.println("Hello from MyClass inside mypackage");  
    }  
}

👉Step 2: Save and Compile the File:

Save the file as MyClass.java and compile using:

sh

javac -d . MyClass.java  

The -d . option creates a directory with the package name (mypackage).

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👉How to Use a Package in Java?

1. Importing a Package

To access a class from another package, import it using import keyword:

java

import mypackage.MyClass;  

public class TestPackage {  
    public static void main(String args[]) {  
        MyClass obj = new MyClass();  
        obj.showMessage();  
    }  
}

2. Importing All Classes from a Package:

Use * to import all classes from a package:

javaCopyEditimport mypackage.*;  

3. Using Fully Qualified Name:

Without import, you can directly use the fully qualified name:

java

mypackage.MyClass obj = new mypackage.MyClass();

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👉Creating Sub-Packages in Java:

A sub-package is a package inside another package.

👉Steps to Create a Sub-Package:

Modify the package name with . (dot notation):

java

package mypackage.subpackage;  

public class SubClass {  
    public void display() {  
        System.out.println("Inside SubClass of subpackage");  
    }  
}

Compile:

shCopyEditjavac -d . SubClass.java  

Execute:

sh

java mypackage.subpackage.SubClass  

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👉Advantages of Using Java Packages Properly:-

• Better Code Organization: Helps in structuring large projects efficiently.
• Enhanced Code Reusability: Easily reuse classes across different projects.
• Improved Readability: Keeps code maintainable and modular.
• Naming Conflict Prevention: Avoids clashes between class names in large applications.

By structuring Java programs into well-defined packages, developers can create scalable and manageable codebases. Keep following best practices for efficient and error-free Java development! 🚀