Substract 1 after each loop end

I'm new at java and i tried to make a Guess The Number game.

When the loop starts, i want to check if the user has any tries left.

if (remain > 1);

then after each end of the loop I want to subtract 1 from the tries.
I also tried to gather 1 after each loop ends.

byte tries = 5, remain=(byte)(--tries);

When user is out of tries i want to break the loop and break the game:

else if (remain == 0){
     System.out.println("You haven't guessed the number!");
     break;
   }

Here's my code:

public class Master{
    private static Scanner scanner = new Scanner(System.in);

    public static void main(String[] args) {
        double number = (byte)(Math.random() * 21);

        while(true){
            // User input
            System.out.print("Choose a number between 1 and 21 :");

            byte user = scanner.nextByte();
            byte tries = 5, remain=(byte)(--tries);
            System.out.println(remain);
          
            if (remain > 1);
                //game
                if (user==number){
                    System.out.println("You have guessed the number!");
                    break;
                } else if (user < number)
                    System.out.println("You are lower than the number!");
                else if (user > number)
                    System.out.println("You are higher than the number!");

            //Break if user is out of tries
            else if (remain == 0){
                System.out.println("You haven't guessed the number!");
                break;
            }
            
        }
    }
}

Code works perfectly but it won't break when user is out of tries.

tries variable should be initialized outside the while loop and the if statement was being closed using a ';'

private static Scanner scanner = new Scanner(System.in);

    public static void main(String[] args) {
        double number = (byte)(Math.random() * 21);
        byte tries = 5;  // tries should be initialized outside the loop
        while(true){
            // User input
            System.out.print("Choose a number between 1 and 21 :");

            byte user = scanner.nextByte();
        
            byte remain=(byte)(--tries);
            System.out.println(remain);
          
            if (remain > 1) { // You were using ; and this if statement was closed
                //game
                if (user==number){
                    System.out.println("You have guessed the number!");
                    break;
                } else if (user < number)
                    System.out.println("You are lower than the number!");
                else if (user > number)
                    System.out.println("You are higher than the number!");
            }
            //Break if user is out of tries
            else if (remain == 0){
                System.out.println("You haven't guessed the number!");
                break;
            }
               
        }
    }

I think you are misunderstanding a lot of concepts. Here's a commented version :

public class Master {
    private static Scanner scanner = new Scanner(System.in);

    public static void main(String[] args) {
        // The number to found
        double numberToFound = (byte)(Math.random() * 21);
        // The user number will be stored here
        byte userInput = 0;
        // The number of tries left
        byte tryLeft = (byte) 5;
        
        do { 
            // Ask the User an number
            System.out.print("Choose a number between 1 and 21 :");
            userInput = scanner.nextByte(); // Store it
            
            // Test the number
            if (userInput > numberToFound) {
                System.out.println("You are lower than the number!");
            } else {
                System.out.println("You are higher than the number!");
            }
            tryLeft--; // We remove one try
        } while(tryLeft > 0 && userInput != numberToFound); // We loop until there are no more try OR we found the number

        // Last time check (we check why we exited the loop)
        // The user found the number
        if (numberToFound == userInput)
            System.out.println("You have guessed the number!");
        else // The user has no more tries left
            System.out.println("You haven't guessed the number!");
    }
}

You should avoid using while(true) if you have a breaking condition for better readability.

You can try this code.

I changed some datatypes and added the decreasing of the remain variable inside the loop.

public class Master{
    private static Scanner scanner = new Scanner(System.in);

    public static void main(String[] args) {
        int number = (int)(Math.random() * 21);
        
        int tries = 5;
        int remain = tries;
        
        while(true){
            System.out.print("Choose a number between 1 and 21:");
            int user = scanner.nextInt();

            // User input
            System.out.println(remain);
          
            if (remain > 1) {
                //game
                if (user==number){
                    System.out.println("You have guessed the number!");
                    break;
                } else if (user < number)
                    System.out.println("You are lower than the number!");
                else if (user > number)
                    System.out.println("You are higher than the number!");
                --remain;
            }
            //Break if user is out of tries
            else if (remain == 0){
                System.out.println("You haven't guessed the number!");
                break;
            }
            
        }
    }
}      

First of all, you can check if the "remain" is bigger than 0 and not 1, and your code will do the job as you planned (and you don't need to check == 0 at the else)

Second of all small comments to make your code more arranged:

1. Work with parameters that are comfortable to you like int (easier to debug and work with) you should use byte only if the code really needs it.
2. Move parameters that you use only to check them outside the loop like tries (think on that you will define this variable on every loop iteration and you don't need to).
3. Add to the params you are not going to change (like tries & number after you moved outside the loop) final it will be more clear that you are not going to change this param anymore.

Other than that looks great, good luck!