java - Error incompatible types. Postfix evaluation -


my task create program postfix evaluation using array , char. i'm having trouble problem

incompatible type: object cannot converted int.

here's code:

import java.util.*; public class stackpostfixeva { //class name   public static void main(string args[]) {      scanner key = new scanner(system.in); //initialize scanner     char[] postfix = new char[10]; //creating array      system.out.println("please enter postfix expression. enter '#' if have finish entering postfix expression ");  //instruction command     int i; //initialize variable     (i = 0; <= postfix.length; i++) { //loop receiving input       postfix[i] = key.next().charat(i); //input command       if (postfix[i] == '#') { //to indicate end         break;       }     }     system.out.println("the postfix expression are:"); //to print postfix        expression     (i = 0; <= postfix.length; i++) {       system.out.println(postfix[i]);     }     stack st = new stack(); //creating stack     int result, ch1, ch2; //initialize variable     (i = 0; <= postfix.length; i++) { //loop scanning each char       if (postfix[i] >= '0' && postfix[i] <= '9') { //to determine operand         st.push((int) postfix[i] - '0'); //push operand       }        else        { //execution if operator found         ch1 = st.pop(); //problem here         ch2 = st.pop(); //problem here         switch (postfix[1]) {           case '+':             result = ch2 + ch1;             break;           case '-':             result = ch2 - ch1;             break;           case '*':             result = ch2 * ch1;             break;           case '/':             result = ch2 / ch1;             break;           case '%':             result = ch2 / ch1;             break;           default:             result = 0;         } //end switch         st.push(result);       } //end else     } //end     result = st.pop(); //problem here     system.out.println(result);   } }

you using stack store integer values, i'd suggest specifying generic type:

stack<integer> st = new stack<>();

that way st.pop() have type integer , autoboxed int.

when declare stack (with no type parameters), pop() returns object not convertible int without explicit cast (offered in answer).


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