Thread: What does this code output?

I can't seems to get the output of this code to display in the console window, evening after implementing a System.out.println() for each variable. Could someone give me some suggestion or possible output for the code, thanks.

 public class Evaluate
{
public static void main(String[] args)
{
Stack<String> ops = new Stack<String>();
Stack<Double> vals = new Stack<Double>();
while (!StdIn.isEmpty())
{ // Read token, push if operator.
String s = StdIn.readString();
if (s.equals("(")) ;
else if (s.equals("+")) ops.push(s);
else if (s.equals("-")) ops.push(s);
else if (s.equals("*")) ops.push(s);
else if (s.equals("/")) ops.push(s);
else if (s.equals("sqrt")) ops.push(s);
else if (s.equals(")"))
{ // Pop, evaluate, and push result if token is ")".
String op = ops.pop();
double v = vals.pop();
if (op.equals("+")) v = vals.pop() + v;
else if (op.equals("-")) v = vals.pop() - v;
else if (op.equals("*")) v = vals.pop() * v;
else if (op.equals("/")) v = vals.pop() / v;
else if (op.equals("sqrt")) v = Math.sqrt(v);
vals.push(v);
} // Token not operator or paren: push double value.
else vals.push(Double.parseDouble(s));
}
StdOut.println(vals.pop());
}
}

These forums don't work like that. Perhaps you should be getting to the root of the problem - like why you see no output (does it compile?) - rather than asking someone to do your work for you

Step 1: Format your code to be easily readable (i.e. add tabs).

Step 2: What issue are you running into specifically? Compiler errors? Runtime errors? Which ones?

fyi, StdOut and StdIn are not defined by default in Java, use System.out and System.in instead.

Originally Posted by copeg

These forums don't work like that. Perhaps you should be getting to the root of the problem - like why you see no output (does it compile?) - rather than asking someone to do your work for you

That what I really meant to ask? I tried compiling this program several times but did't see any output. So, copeg or anyone could you give me any suggestion on why I'm not seeing any output when I run this code. Hey, I any revise it a little to showing that I am really putting effort into this. Here is the revise version:

import java.io.BufferedInputStream;
import java.lang.*;
import java.util.*;
import java.util.Scanner;
import java.io.PrintWriter;
import java.io.UnsupportedEncodingException;
import java.util.Locale;
 
 
public class StdIn {
 
	 private static Scanner scanner = new Scanner(new BufferedInputStream(System.in));
 
 
	 public static boolean isEmpty() {
	        return !scanner.hasNext();
	    }
 
	 public static String readString() {
	        return scanner.next();
	    }
 
 
 
	public  static void main (String args[]){ 
 
 
		//InputStreamReader input = new InputStreamReader(System.in);
		//BufferedReader reader = new BufferedReader(input);
 
		Stack<String> ops = new Stack<String>();
 
		Stack<Double> vals = new Stack<Double>();
		//String s = reader.readLine();
 
 
 
		while (!StdIn.isEmpty())
		{ // Read token, push if operator.
			String s = StdIn.readString();
		if (s.equals("(")) ;
		else if (s.equals("+")) ops.push(s);
		else if (s.equals("-")) ops.push(s);
		else if (s.equals("*")) ops.push(s);
		else if (s.equals("/")) ops.push(s);
		else if (s.equals("sqrt")) ops.push(s);
		else if (s.equals(")"))
 
		{ // Pop, evaluate, and push result if token is ")".
		String op = ops.pop();
		double v = vals.pop();
		if (op.equals("+")) v = vals.pop() + v;
		else if (op.equals("-")) v = vals.pop() - v;
		else if (op.equals("*")) v = vals.pop() * v;
		else if (op.equals("/")) v = vals.pop() / v;
		else if (op.equals("sqrt")) v = Math.sqrt(v);
		vals.push(v);
		System.out.println(vals.push(v));
		} // Token not operator or paren: push double value.
		else vals.push(Double.parseDouble(s));
		System.out.println(Double.parseDouble(s));
 
		}
		System.out.println(vals.pop());	
 
 
 
	}
 
 
 
 
 
	}

The current issue I am having with this code is: figuring out why don't I see any output. I take some of your suggestion: Here is a revise version of my code:

          //import java.io.*;
	//import java.math.*;
	//import java.io.OutputStreamWriter;
	import java.io.BufferedInputStream;
	//import java.lang.*;
	import java.util.*;
	import java.util.Scanner;
	//import java.io.PrintWriter;
	//import java.io.UnsupportedEncodingException;
	//import java.util.Locale;
 
 
	public class StdIn {
 
	private static Scanner scanner = new Scanner(new BufferedInputStream(System.in));
 
 
	 public static boolean isEmpty() 
		 { return !scanner.hasNext();}
 
 
	 public static String readString() 
		 { return scanner.next();}
 
 
 
	public  static void main (String args[]){ 
 
 
	Stack<String> ops = new Stack<String>();
 
	Stack<Double> vals = new Stack<Double>();
 
 
 
	while (!StdIn.isEmpty())
	{ // Read token, push if operator.
		String s = StdIn.readString();
	if (s.equals("(")) ;
	else if (s.equals("+")) ops.push(s);
	else if (s.equals("-")) ops.push(s);
	else if (s.equals("*")) ops.push(s);
	else if (s.equals("/")) ops.push(s);
	else if (s.equals("sqrt")) ops.push(s);
	else if (s.equals(")"))
 
	{ // Pop, evaluate, and push result if token is ")".
	String op = ops.pop();
	double v = vals.pop();
	if (op.equals("+")) v = vals.pop() + v;
	else if (op.equals("-")) v = vals.pop() - v;
	else if (op.equals("*")) v = vals.pop() * v;
	else if (op.equals("/")) v = vals.pop() / v;
	else if (op.equals("sqrt")) v = Math.sqrt(v);
	vals.push(v);
	System.out.println(vals.push(v));
	} // Token not operator or paren: push double value.
	else vals.push(Double.parseDouble(s));
	System.out.println(Double.parseDouble(s));
 
	}
	System.out.println(vals.pop());	
 
 
	}
 
 
	}