Packages in java with example


What is packages?

A package is a grouping of related types providing access protection and name space management. Note that types refers to classes, interfaces, enumerations, and annotation types. 

A package is a collection of related classes.

It helps Organize your classes into a folder structure and make it easy to locate and use them.

More importantly, It helps improve re-usability.

 

Creating a class inside a package


                Create a directory structure as shown in image

 

Main.java

public class Main
{
	// your code
}

Vehicle.java

           If your code belongs to package then your programs first line should be

                                package <packagename>

package sam;

public class Vehicle
{
	public  int a = 10
    //your code
}

Car.java

package sam.test;

public class Car
{
	// your code
}

 

Accessing a class located in different package

There are two ways to access class located in another package

1.       Use import statement to access the class

 

Star(*) imports all classes located in the package specified.

import sam.*; 

import sam.test.*;

 

But the best practice is to import only the specific class

import sam.Vehicle;

import sam.test.Car;

 

To access vehicle and car class in Main

import sam.Vehicle;
import sam.test.Car;

class Main
{
	public static void main(String[] args)
	{
		Vehicle v1 = new Vehicle();
		System.out.println(v1.i);
	}
}

Compile all classes and run Main.java to check the output

 

2.       Instead of importing the class you can import it while creating the object

sam.test.Vehicle v1=new sam.test.Vehicle();

 class Main
{
	public static void main(String[] args)
	{
		sam.test.Vehicle v1 = new sam.test.Vehicle();
		System.out.println(v1.i);
	}
} 

This type of import will be used to avoid import conflicts when we have same class name in different package




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