I can compile but can't run

This is the DotCome game in HFJ. I can compile it but when I try to run it I get the error message
D:\MyFiles>java S1
Exception in thread "main" java.lang.NoClassDefFoundError: S1.

Below is the code

import java.io.*;
 
 public class S1{

public static void main(String[] args){
SimpleDotCom dot=new SimpleDotCom();
int numbofGuesses=0;
GameHelper helper=new GameHelper();

int randNum=(int)(Math.random()*5);
int[] locations={randNum,randNum+1,randNum+2};

dot.setLocationCells(locations);
boolean isAlive=true;

while(isAlive==true){
String guess=helper.getUserInput("Enter a Number");
String result=dot.checkYourself(guess);
numbofGuesses++;
if(result.equals("kill")){
isAlive=false;
System.out.println("You took "+numbofGuesses+"guesses");
    }

}
}
}
 class SimpleDotCom{
int[] locationCells;
int numOfHits=0;
 
public void setLocationCells(int[] locs){
locationCells=locs;
}
 
public String checkYourself(String stringGuess){
int guess=Integer.parseInt(stringGuess);
String result="miss";
for(int cell:locationCells){
if(guess==cell){
result="hit";
numOfHits++;
break;
}
}

if(numOfHits==locationCells.length){

result="kill";
}
System.out.println(result);
return result;
}//close method
}

//game Helper class
class GameHelper{
public String getUserInput(String prompt){
String inputLine=null;
System.out.println(prompt+"");
try{
BufferedReader is=new BufferedReader(new InputStreamReader(System.in));
inputLine=is.readLine();
if(inputLine.length()==0) return null;
}catch(IOException e){
System.out.println("IOException"+ e);
}
return inputLine;
}
}

What am I doing wrong? Any help would be welcome

When you put the below on your dos prompt, what do you see?

You may have an issue about classpath. You can view the FAQ #9.

http://faq.javaranch.com/view?JavaRanchFaq

This is what I get:

D:\MyFiles>set CLASSPATH
CLASSPATH=C:\Program Files\Java\jre1.5.0_10\lib\ext\QTJava.zip

Originally posted by Tontang Bei:
This is what I get:

D:\MyFiles>set CLASSPATH
CLASSPATH=C:\Program Files\Java\jre1.5.0_10\lib\ext\QTJava.zip

You should know that that error you had means, that the class file mentioned cannot be found.

The classpath should include the folder or path where your classes (those files generated when you compiled your source code) are.

The dot character '.' represents the current directory. If the classes are in same folder where you are executing the run, the dot should be in the classpath. For example (Notice the dot after the = sign?):

On how to set the classpath, the FAQ might have it.
[ February 18, 2007: Message edited by: Jesus Angeles ]

Just a quick fix if your situation is:
>>>no package
>>>the classes are in the folder where you executed the 'java' to run the program

Put this in your dos prompt, press enter, and run again