Infix_to_Postfix.java

package com.company;
import java.util.Stack;
public class Infix_to_Postfix {
    static int Precedence(char ch){
        switch (ch){
            case '+':
            case '-':
                return 1;
            case '*':
            case '/':
                return 2;
            case '^':
                return 3;
        }
        return -1;
    }
    static String infixToPostfix(String exp){
        String result = new String("");
        Stack<Character> stack = new Stack<>();
        for (int i = 0; i<exp.length(); ++i) {
            char c = exp.charAt(i);
            if (Character.isLetterOrDigit(c))
                result += c;
            else if (c == '(')
                stack.push(c);
            else if (c == ')')
            {
                while (!stack.isEmpty() &&
                        stack.peek() != '(')
                    result += stack.pop();
                stack.pop();
            }
            else
            {
                while (!stack.isEmpty() && Precedence(c) <= Precedence(stack.peek())){
                    result += stack.pop();
                }
                stack.push(c);
            }
        }
        while (!stack.isEmpty()){
            if(stack.peek() == '(')
                return "Invalid Expression";
            result += stack.pop();
        }
        return result;
    }
    public static void main(String[] args) {
        String exp = "a+b*(c^d-e)";
        System.out.println(infixToPostfix(exp));
    }
}