Post Fix evaluator

I don't know how you tested it, but this prints out 45 as expected:

   public static void main (String args[]) {
      PostfixEvaluator pe = new PostfixEvaluator();
      System.out.println( pe.evaluate("20 5 - 3 *") );
   }

Well, I must say that I changed StackADT to Stack (to get it compiled):

   import java.util.Stack;   // << added

   //private StackADT stack;   // replaced by:
   private Stack stack;

   //-----------------------------------------------------------------
   //  Sets up this evalutor by creating a new stack.
   //-----------------------------------------------------------------
   public PostfixEvaluator()
   {
       // stack = new LinkedStack();   // replaced by:
       stack = new Stack();
   }

Code looks fine, check that you have compiled all the classes.

zzynx:
when i use your code   System.out.println( pe.evaluate("20 5 - 3 *") );

i get the correct answer same as you, however, i want the expression to be inputted by the user so when i go back to the way my code was i keep gettin 0 outputted. I didnt even have to change StackADT as mine compiles fine.

public class UsePostFixEvaluator
{
      public static void main (String args[])
      {
            PostfixEvaluator evalTest = new PostfixEvaluator();
            //receives expression from user
            System.out.println("Enter expression");
            String expression = uuInOut.ReadString();
            

      System.out.println("Result: " +evalTest.evaluate(expression));
      }
}


objects: ta for reply but all classes are compiled

:)

Could you replace
>> System.out.println("Result: " +evalTest.evaluate(expression));
by
System.out.println("expression=" + expression + " - Result: " +evalTest.evaluate(expression));

and post here what that gives.

expression = 20 - Result: 0


thanks for reply

ahhh ok,


i will try a Buffered Reader instead and let u know :)

thanks again

pete

You're welcome :)

u were spot on,

much appreciated


pete

Thanks for accepting

PS. Any reason why I got a B-grade?

sorry i didnt mean any offence by it,

if i can change it i will,
i just thot the top grade would be used more sparingly but i see what u mean, y say just good when u just got me out of a situation i was stumped at.

i will see if i can change it.

I'll ask a mod to reopen this Q.
Afterwards you can just reaccept.

ok sounds fair

>> sorry i didnt mean any offence by it,
No worries, I didn't interprete is a such, you know ;°)

>>Grade changed to A.
Thanks

>> For grade changes there is no need to reopen the question
Right, I forgot that.