Problem evaluate reverse Polish notation

Problem description:

Evaluate the value of an arithmetic expression in reverse Polish notation.

Valid operators are+,-,*,/. Each operand may be an integer or another expression.

Solution:

 1   Public   Int  Evalrpn (string [] tokens ){  2 Stack <string> operands = New Stack <string>();  3           For ( Int I = 0; I <tokens. length; I ++ ){  4               If (! (Tokens [I]. equals ("+") | tokens [I]. equals ("-") | tokens [I]. equals ("*") | tokens [I]. equals ("/" ))){  5   Operands. Push (tokens [I]);  6 } Else  {  7 String opright = Operands. Pop ();  8 String opleft = Operands. Pop ();  9 String result = "" ;  10                   If (Tokens [I]. Equals ("+" )){  11 Result = string. valueof (integer. valueof (opleft) + Integer. valueof (opright ));  12 } Else  If (Tokens [I]. Equals ("-" )){  13 Result = string. valueof (integer. valueof (opleft )- Integer. valueof (opright ));  14 } Else   If (Tokens [I]. Equals ("*" )){  15 Result = string. valueof (integer. valueof (opleft )* Integer. valueof (opright ));  16 }Else   If (Tokens [I]. Equals ("/" )){  17 Result = string. valueof (integer. valueof (opleft )/ Integer. valueof (opright ));  18   }  19   Operands. Push (result );  20   }  21   }  22  23           Return  Integer. valueof (operands. Pop ());  24 }