Authentication is the process of verifying the identity of users or information. User authentication is the process of verifying the identity of the user when that user logs in to a computer system. The main objective of authentication is to allow authorized users to access the computer and to deny access to unauthorized users.

Example

Default Assumption: User name = Geeks For Geeks , Password = Geeks For Geeks

Input: User name = Geeks For Geeks, Password = Geeks For Geeks
Output: Authentication Successful

Input: User name = Geeks For Geeks, Password = Hello world
Output: User name/ Password not matching

Approach:

1. Take username and password as string input from the user.
2. Check if the username matches the password or not.
3. If it matches then welcome the user.
4. Else display an appropriate message.

Below is the implementation of the above approach

// Java program to check the authentication of the user

// Importing the modules
import java.util.*;

// Gfg Class
public class Gfg
{
	// Main CLass
	public static void main(String args[])
	{
		// Declaring the username and password
		String user_name = "Geeks For Geeks";
		String password = "Geeks For Geeks";
		
		// Checking the validity of the input
		if(user_name.equals("Geeks For Geeks") && password.equals("Geeks For Geeks"))
		{
			// Printing Output
			System.out.println("Authentication Successful");
		}
		else
		{
			// Printing Output
			System.out.println("User name/ Password not matching");
		}
	}
}

Output

Authentication Successful