Scanner java class not working as expected

Question

strong text Very simple code should get inputs int from the user until no valid int information is entered and print out the min and max values after that. But I get two different problems:

First for some unknow reason the first "Enter a number:" shows after the first number is entered.

Second it crashes after no int information is entered even after the scanner.hasNextInt(); validation.

public static void minMaxChallenge() {
    Scanner scanner = new Scanner(System.in);
    int minValue = -1;
    int maxValue = -1;
    int counter = 0;
    boolean isAnInt = scanner.hasNextInt();

    while (true) {
        System.out.println("Enter a number: ");
        if (isAnInt) {
            int number = scanner.nextInt();

            if (counter == 0) {
                minValue = number;
                maxValue = number;
            } else if (number > maxValue) {
                maxValue = number;
            } else if (number < minValue) {
                minValue = number;
            }
            counter++;
        } else {
            System.out.println("Invalid Number Entered");
            break;
        }
        scanner.nextLine();
    }
    System.out.println("Your Maximum value entered is: " + maxValue);
    System.out.println("Your Minimum value entered is: " + minValue);
    scanner.close();
}