I have written a simple lexer file from which JFlex has generated a Lexer.java file with no complaints. 

However I cannot compile the Lexer.java file without the error: 

package java\_cup.runtime does not exist

I don't understand what the problem is, as I followed a tutorial which said that as long as the java-cup-11a.jar file is in the root folder then there shouldn't be any classpath problems. 

I have spent hours trying to fix this and would appreciate any help.