Guess Num Higer Or Lower

We are playing the Guess Game. The game is as follows:

I pick a number from 1 to n. You have to guess which number I picked.

Every time you guess wrong, I'll tell you whether the number is higher or lower.

You call a pre-defined API guess(int num) which returns 3 possible results (-1, 1, or 0):

Have you met this question in a real interview?  
Example
n = 10, I pick 4 (but you don't know)

Return 4. Correct !

public class Solution extends GuessGame {
    /**
     * @param n an integer
     * @return the number you guess
     */
    public int guessNumber(int n) {
        // Write your code here

        //be careful, -1 is my number is lower which means mid is larger than the target number ,need to move end to mid
        int start = 0, end = n;
        while(start + 1 < end){
            int mid = start + (end - start)/2;
            
            if(guess(mid) == 0){
                return mid;
            }else if(guess(mid) == -1){
                end = mid;
            }else{
                start = mid;
            }
        }
        
        System.out.println(start+" "+end);
        if(guess(start) == 0){
            return start;
        }
        if(guess(end) == 0){
            return end;
        }
        
        return -1;
    }
}