postfix.java

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

public class postfix{
    public static int postfixEvaluate(String expression) {
        Stack<Integer> stack = new Stack<>();
        for (char c : expression.toCharArray()) {
            if (Character.isDigit(c)) {
                stack.push(c - '0');
            } else {
                int operand2 = stack.pop();
                int operand1 = stack.pop();
                int result = applyOperator(operand1, operand2, c);
                stack.push(result);
            }
        }
        return stack.pop();
    }

    public static int applyOperator(int operand1, int operand2, char operator) {
        switch (operator) {
            case '+':
                return operand1 + operand2;
            case '-':
                return operand1 - operand2;
            case '*':
                return operand1 * operand2;
            case '/':
                if (operand2 == 0) {
                    throw new ArithmeticException("Division by zero");
                }
                return operand1 / operand2;
            default:
                throw new IllegalArgumentException("Invalid operator");
        }
    }

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        System.out.println("Enter the postfix expression:");
        String postfixExpression = sc.nextLine();
        int result = postfixEvaluate(postfixExpression);
        System.out.println("Result of the postfix expression: " + result);
        sc.close();
    }
}