expressionSolver

import java.util.ArrayList;
import java.util.Scanner;
import static java.lang.Integer.*;
import static java.lang.System.*;

public class ExpressionSolverRunner {
    public static void main(String[] args) {
        Scanner input = new Scanner(System.in);
        /*
         * System.out.print("Enter an operation: "); String a =
         * input.nextLine(); ExpressionSolver calc = new ExpressionSolver();
         * System.out.println("Result: " + calc.solve(a));
         */
        System.out.print("Type expression: ");

        ArrayList<String> equation = new ArrayList<String>();
        equation = format(input.next());
        System.out.println(solve(equation));
    }

    public static ArrayList<String> format(String str) {
        ArrayList<String> equation = new ArrayList<String>();
        for (int i = 0; i < str.length(); i++) {
            if (str.charAt(i) != ' ') {
                equation.add("" + str.charAt(i));
            }
        }
        return equation;
    }

    public static ArrayList<String> solve(ArrayList<String> equation) {
        while (equation.size() != 1) {
            for (int i = 0; i < equation.size() - 1; i++) {
                if (equation.get(i).equals("*")) {
                    equation.set(i, Double.toString(
                            Double.parseDouble(equation.get(i - 1)) * Double.parseDouble(equation.get(i + 1))));
                } else if (equation.get(i).equals("/")) {
                    equation.set(i, Double.toString(
                            Double.parseDouble(equation.get(i - 1)) / Double.parseDouble(equation.get(i + 1))));
                }
                equation.remove(i - 1);
                equation.remove(i + 1);
            }
            for (int i = 0; i < equation.size() - 1; i++) {
                if (equation.get(i).equals("+")) {
                    equation.set(i, Double.toString(
                            Double.parseDouble(equation.get(i - 1)) + Double.parseDouble(equation.get(i + 1))));
                } else if (equation.get(i).equals("/")) {
                    equation.set(i, Double.toString(
                            Double.parseDouble(equation.get(i - 1)) * Double.parseDouble(equation.get(i + 1))));
                }
                equation.remove(i - 1);
                equation.remove(i + 1);
            }
        }
        return equation;
    }
}