M(m...)

package stackz;

import java.util.*;

public class StackZ {

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        Stack m = new Stack();
        System.out.print("Введите строку: ");
        String s="";
        int sch = 99;
        while (sch == 99) {
            s = sc.nextLine();
            sch = 0;
            for (int i = 0; i < s.length(); i++) {
                if (s.charAt(i) == '(') {
                    sch++;
                } else if (s.charAt(i) == ')') {
                    sch--;
                }
                if (sch < 0) {
                    sch = 99;
                    break;
                }
            }
            if (sch != 0) {
                System.out.println("Строка введена некорректно. Повторите ввод.");
                sch = 99;
            }
        }
        int y;
        char[] mas = s.toCharArray();
        int a, b = 0;
        for (int i = s.length() - 1; i > -1; i--) {
            y = s.charAt(i);
            if (y != (int) '(' || y != (int) ')' || y != (int) ',') {
                if (y >= (int) '0' && y <= (int) '9') {
                    m.push(mas[i]);
                } else if (y == (int) 'M' || y == (int) 'm') {
                    try {
                        a = (int) (char) m.peek();

                    } catch (ClassCastException e) {
                        a = (int) m.peek();
                    }
                    //System.out.println((char)a);
                    if (!m.empty()) {
                        m.pop();
                    }
                    try {
                        b = (int) (char) m.peek();
                    } catch (ClassCastException e) {
                        b = (int) m.peek();
                    } catch (EmptyStackException e) {
                        b = a;
                    }
                    //System.out.println((char)b);
                    if (!m.empty()) {
                        m.pop();
                    }
                    /*if (!m.empty()) {
                        m.pop();
                    }*/
                    if (y == (int) 'M') {
                        if (a > b) {
                            m.push(a);
                            //System.out.println("="+(char)a);
                        } else {
                            m.push(b);
                            //System.out.println("="+(char)b);
                        }
                    }
                    if (y == (int) 'm') {
                        if (a < b) {
                            m.push(a);
                            //System.out.println("="+(char)a);
                        } else {
                            m.push(b);
                            //System.out.println("="+(char)b);
                        }
                    }
                }
            }
        }
        System.out.println(((char) (int) m.peek()));
    }
    // M(3,m(2,3))
    //Введите строку: m(m(m(3,M(3,4)),2),4)
}