<s>[INST] Here is a simple Java code snippet that shows a login system with a single username and password combination. The program will only allow you to login if you enter "admin" for both the username and password.
```java
import java.util.Scanner;

public class Login {
    public static void main(String[] args) {
        Scanner input = new Scanner(System.in);

        String username = "admin", password = "admin";

        System.out.println("Login System");
        System.out.println("------------");

        System.out.print("Enter username: ");
        String enteredUsername = input.nextLine();

        System.out.print("Enter password: ");
        String enteredPassword = input.nextLine();

        if (enteredUsername.equals(username) && enteredPassword.equals(password)) {
            System.out.println("Login successful!");
        } else {
            System.out.println("Invalid username or password!");
        }
    }
}
```

I want to modify the code to use a HashMap so that I can add more users to the system. Please modify the code to use a HashMap.

Here is an example of what I'd like the output to look like:
```
Login System
------------
Enter username: user1
Enter password: pass1
Invalid username or password!

Enter username: admin
Enter password: admin
Login successful!

Enter username: user1
Enter password: pass1
Invalid username or password!

Enter username: root
Enter password: root
Invalid username or password!
```

Here is what I imagine the HashMap will look like (or at least how I think it should look like):

`HashMap<String, String> users = new HashMap<String, String>();`

With the following key-value pairs:

`users.put("admin", "admin");`

`users.put("user1", "pass1");`

`users.put("root", "root");`

I'd like the program to keep running and asking for input until the user enters "exit" as the username.

Here is what I'd like the overall output to look like:
```
Login System
------------
Enter username: admin
Enter password: admin
Login successful!

Enter username: user1
Enter password: pass1
Login successful!

Enter username: root
Enter password: root
Login successful!

Enter username: exit
Exiting program...
```

Here is what I have so far. I've added the HashMap and a while loop to keep asking for input, but I'm having trouble getting the logic to work correctly.
```java
import java.util.HashMap;
import java.util.Map;
import java.util.Scanner;

public class Login {
    public static void main(String[] args) {
        Scanner input = new Scanner(System.in);

        Map<String, String> users = new HashMap<String, String>();
        users.put("admin", "admin");
        users.put("user1", "pass1");
        users.put("root", "root");

        System.out.println("Login System");
        System.out.println("------------");

        while (true) {
            System.out.print("Enter username: ");
            String enteredUsername = input.nextLine();

            if (enteredUsername.equals("exit")) {
                System.out.println("Exiting program...");
                break;
            }

            System.out.print("Enter password: ");
            String enteredPassword = input.nextLine();

            // This is where I'm having trouble. How do I check if the entered username
            // and password are in the HashMap?[/INST]