Checking for forbidden words

[überfuzz]

I'm trying to put together a method that check for predefined vars. If a user tries to use a predefined variable not mapping is supposed to take place.

Method to check for predefined.

   static boolean isVarAllowed()
   {
      if(st.getWord() == "e" ||          //getWord() returns String 
         st.getWord() == "pi" ||
         st.getWord() == "sin" ||
         st.getWord() == "cos" ||
         st.getWord() == "log" ||
         st.getWord() == "exp" ||
         st.getWord() == "ans")
      {
         return false; 
      }
      else
      {
         return true;
      }
   }

Usage:

        if(isVarAllowed() == true)
         {
            System.out.println("Test: It's mapping.");
            map.put(st.getWord(), new Double(res));
         }

The mapping works, but I can't get it do deny over mapping. As it is now I'm loosing stuff like pi if the user tries to save stuff in pi. I other words, all mappings are allowed now. Well, as I said, that's not what I what. :-/

[JosAH]

Don't compare Strings for equality like that: use the equals() method. Also, why don't you use a simple Set that contains the forbidden words?

private static final Set<String> forbidden= new HashSet<String>() {{
   add("e");
   add("pi");
   ...
}};

private isMappable(String word) {
   return !forbidden.contains(word);
}

kind regards,

Jos