Infix to Prefix Conversion in Java

import java.util.*;
public class Main
{
    public static int precedence(char op) {
        switch (op) {
            case '+':
            case '-':
                return 1;
            case '*':
            case '/':
            case '%':
                return 2;
            case '^':
                return 3;
        }
        return -1;
    }

    public static String infixToPrefix(String infix) {
        String prefix = "";
        Stack< Character> operators = new Stack< >();

        for (int i = infix.length() - 1; i >= 0; --i) {
            char ch = infix.charAt(i);

            if (precedence(ch) > 0) {
                while (operators.isEmpty() == false &&  precedence(operators.peek()) > precedence(ch)) {
                    prefix += operators.pop();
                }
                operators.push(ch);
            } else if (ch == '(') {

                char x = operators.pop();
                while (x != ')') {
                    prefix += x;
                    x = operators.pop();
                }

            } else if (ch == ')') {
                operators.push(ch);
            } else {
                prefix += ch;
            }
        }

        while (!operators.isEmpty()) {
            prefix += operators.pop();
        }

        String reversedPrefix = "";
        for (int i = prefix.length() - 1; i >= 0; i--) {
            reversedPrefix += prefix.charAt(i);
        }
        return reversedPrefix;
    }

    public static void main (String[]args)
    {
        String exp = "A+B*(C^D-E)";
        System.out.println ("Infix Expression: " + exp);
        System.out.println ("Prefix Expression:" + infixToPrefix (exp));
    }
}