How can I update the new random value in Java?

I just started to learn Java, so my program is made with the most basic codes, and I am having some problems with random numbers. I am suppose to make a program that generates a winning number, then the program itself will try to guess it. And based on the guess is high or low, the program's next guess will be limited in a new range, until it guessed the winning number, just like how humans try to guess the number. However, in the while loop, the random number guess does not update to a new random number based on the new range, and java keeps looping with the same number over and over again infinitely. At first I thought it is because I do not return the new guess value, but return will stop the while loop. I am confused, and I am trying to get some help, thank you very much!

import java.util.Random;

public class GuessNum {  

    public static void main(String[] args) {

        int range;
        range = 0;

        int upper;
        upper = 100;

        int lower;
        lower = 0;

        int finaltotal;
        finaltotal = 0;

        for(int i = 0; i < 1000; i++) {

            int total;
            total = 0;

            int win = (int)(Math.random() * 100 + 1);

            int guess = (int)(Math.random() * 100 + 1);

            while(guess != win) {

                if(guess > win) {

                    String strGuess;
                    strGuess = "Your guess is: " + String.valueOf(guess);
                    System.out.println(strGuess);

                    System.out.println("Guess is high!");

                    upper = guess;

                    range = upper - lower + 1;

                    guess = (int)(Math.random() * range + lower);

                    total += 1;

                }

                if(guess < win) {

                    String strGuess;
                    strGuess = "Your guess is: " + String.valueOf(guess);
                    System.out.println(strGuess);

                    System.out.println("Guess is low!");

                    lower = guess;

                    range = upper - lower + 1;

                    guess = (int)(Math.random() * range + lower);

                    total += 1;

                }

            }

            String strGuess;
            strGuess = "Your guess is: " + String.valueOf(guess);
            System.out.println(strGuess);

            System.out.println("You win!");

            total += 1;

            finaltotal += total;

        }

        int average = finaltotal / 1000;

        String strAverage;
        strAverage = "The average number of guesses is: " + String.valueOf(average);
        System.out.println(strAverage);

}
}