solve_PostFix_STACK.java

import java.util.Stack;

public class solve_PostFix_STACK {
    static void stackPostfix(String pf) {
        Stack<Integer> st = new Stack<>();

        for (int i = 0; i < pf.length(); i++) {
            char c = pf.charAt(i);

            if (Character.isDigit(c))
                st.push(c - '0');

            else {
                int v1 = st.pop();
                int v2 = st.pop();

                switch (pf.charAt(i)) {

                    case '+': {
                        st.push(v2 + v1);
                        break;
                    }

                    case '-': {
                        st.push(v2 - v1);
                        break;
                    }

                    case '*': {
                        st.push(v2 * v1);
                        break;
                    }

                    case '/': {
                        st.push(v2 / v1);
                        break;
                    }
                }
            }
        }

        System.out.println(st);
    }
}