Infix.java

import java.util.Stack;
import java.util.Scanner;

public class Infix {
	public static int evaluate(String expression) {
		//char[] nextItem = expression.toCharArray();
		String[] nextItem = expression.split(" ");
		Stack<Integer> operands = new Stack<>();
		Stack<String> operators = new Stack<>();

		for( int i = 0; i <= nextItem.length - 1; i ++) {
			if(nextItem[i].charAt(i) >= '0' && nextItem[i].charAt(i) <= '9') {
				operands.push((int)(nextItem[i].charAt(i)));
			}
			else {
				double operand2 = operands.pop();
				double operand1 = operands.pop();
				double result = applyOperator(nextItem[i], operand1, operand2);
				operands.push((int)result);

			}
		}

		return operands;
	}
	
		public static double applyOperator(String string, double first, double second) {
		if(string == "+")
			return first + second;
		//else if(string == "-")
			//return first - second;
		else if(string == "*")
			return first * second;
		else if(string == "/") {
			if(second == 0)
				throw new UnsupportedOperationException("Cant divide by 0");
			return first / second;}
		else if(string == "^")
			return Math.pow(first, second);
		else
			/*try {
				throw new Exception("Invalid Operator");
			} catch (Exception e) {
				// TODO Auto-generated catch block
				e.printStackTrace();
			}*/
			return first - second;
	}
	public static void main(String[] args) {
		Scanner input = new Scanner(System.in);
		System.out.println("Please enter a expression: ");
		String userInput = input.nextLine();
		System.out.println(evaluate(userInput));
		//evaluate(userInput);



	}

}