import java.util.*;






public class Calc {




    int rc;
    static int src;
    double result;
    double evalexpr;
    double m;
    String s;
    String token;
    String operator;
    String expr;
    String peektoken;
    int cursor = 0;


    public static void main(String[] args)
    {
     Calc x = new Calc();
     src = x.process();

     return;
    }




    private int process()
    {
        Scanner sc = new Scanner(System.in);
        System.out.println("Enter an expression");
        s = sc.nextLine();

        boolean keepgoing = true;
        while(keepgoing == true)
           {
            s = sc.nextLine();
            System.out.println("Hello from evalte123rm");
            s = s.trim();
                if (s== null)
               {



                System.out.println("The input is" + token);
                result = evalexpr();
                keepgoing = false;
                continue;
               }
           }

      return s;
    }



    double evalterm()
    {
       double a = evalfactor();
       token = peektoken();
           System.out.println("Hello from evalterm");
        if((token.equals("*")) || (token.equals("/")))
        {
            System.out.println("Hello from evalterm if");
             operator = token;
             cursor++;
             double b = evalfactor();
                if ("*".equals(operator))
                {
                 a=a*b;

                }else{

                 a=a/b;
           }
        }
       return a;
    }

    double evalexpr()
    {
        double x = evalterm();
        System.out.println("Hello from evalexpr");
        token = peektoken();
            double z;

        if((token.equals("+")) || (token.equals("-")))
        {
            operator = token;
            cursor++;
            double y = evalterm();
                if (operator == "+")
                z = x + y;
                else
                z = x - y;
        }
        return x;
    }


    double evalfactor(){

        token = peektoken();
        System.out.println("Hello from evalfactor");
        if(token.equals("("))
        {
            cursor++;
            double K = evalexpr();
           System.out.println("Hello from evalfactor if");
        }

        else{

        cursor++;
        double r = Double.parseDouble(token);

}
        return x;
    }

    private String peektoken() {
        {
        String j = "";
        System.out.println("Hello from str peektoken");
        while(cursor<expr.length())
        {
            j = expr.substring(cursor,cursor+1);

            if(j.matches("[0-9]"))
            {
            return j;
            }
            if(j.equals(" "))
        {
            cursor++;
            System.out.println("Hello from peektoken if");
            continue;
        }
        if(j.matches("[+-*/]"))
        {
        return j;
        }
        System.out.println("Error");
        return j;
        }
    return null;
    }

    }
    String token(){

        System.out.println("Hello from str token");

    }


        }