import java.util.*;

public class PerformInfixExpression {
    private static Stack<String> stack = new Stack<>();
    private static final String OPERATORS = "*/+-";


    public static String evaluateInfix(String exps){
        //Removes all spaces from expression
        exps = exps.replaceAll("\\s+", "");

        //Breaks up expression into tokens
        StringTokenizer tokens = new StringTokenizer(exps, "()*/+-", true);


        while(tokens.hasMoreTokens()){
            String tkn = tokens.nextToken();


            if(tkn.equals("(")
                    || tkn.matches("[0-9]+")
                    || tkn.equals("*")
                    || tkn.equals("/")
                    || tkn.equals("+")
                    || tkn.equals("-")){stack.push(tkn);}
            else if(tkn.equals(")")){
                try {
                    int op2 = Integer.parseInt(stack.pop());

                    String operand = stack.pop();

                    int op1 = Integer.parseInt(stack.pop());

                    if(!stack.empty()){stack.pop();}

                    int result = 0;

//                    switch(operand){
//                        case "*":
//                            result = op1*op2;
//                            break;
//                        case "/":
//                            result = op1/op2;
//                            break;
//                        case "+":
//                            result = op1+op2;
//                            break;
//                        case "-":
//                            result = op1-op2;
//                            break;
//                        default:
//                            break;
//                    }

                    if(operand.equals("*")){
                        result = op1*op2;
                    } else if(operand.equals("/")){
                        result = op1/op2;
                    } else if(operand.equals("+")){
                        result = op1+op2;
                    } else if(operand.equals("-")) {
                        result = op1 - op2;
                    }

                    //Pushes result into stack
                    stack.push(result+"");
                } catch (Exception e) {
                    e.printStackTrace();
                    break;
                }
            }
        }
        String finalResult = "";
        try {
            finalResult = stack.pop();
        } catch (Exception e) {
            e.printStackTrace();
        }
        return finalResult;
    }


    public static void main(String a[]){
        String expr = "((2*5)+(6/2))";
        System.out.println("Expression: "+expr);
        System.out.println("Final Result: "+evaluateInfix(expr));
        expr = "(((2 * 5) - (1 * 2)) / (11 - 9))";
        System.out.println("Expression: "+expr);
        System.out.println("Final Result: "+evaluateInfix(expr));

    }
}