Valid Parenthesis String with Wildcards

/*
 * Problem : Can the stars fix the brackets?
 * Input   : One string.
 * Output  : true or false.
 * Approach: Range of open brackets
 * Time    : O(n)
 * Space   : O(1)
 * Java    : 8 or newer.
 */
import java.util.Scanner;

public class Main {
    // This method solves the task. It receives the input and returns the answer.
    static boolean solve(String s) {
        // Step 1: Keep the smallest and the largest possible number of open brackets at this point.
        int low = 0;
        int high = 0;
        for (int i = 0; i < s.length(); i++) {
            char c = s.charAt(i);
            // Step 2: An open bracket adds one to both. A close bracket removes one from both.
            // Step 3: A star may be open, close or empty, so low goes down and high goes up.
            if (c == '(') {
                low++;
                high++;
            } else if (c == ')') {
                low--;
                high--;
            } else {
                low--;
                high++;
            }
            // Step 4: If even the best case is below zero, a close bracket has no partner.
            if (high < 0) {
                return false;
            }
            // Step 5: The count of open brackets can never be below zero.
            if (low < 0) {
                low = 0;
            }
        }
        // Step 6: It works if zero open brackets is one of the possible results.
        return low == 0;
    }

    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        String s = scanner.hasNextLine() ? scanner.nextLine() : "";
        System.out.println(solve(s));
    }
}