if (lexeme.compareTo("BEGIN")==0) nextToken = BEGIN_CODE;
         else if (lexeme.compareTo("END")==0) nextToken = END_CODE;
         else if (lexeme.compareTo("EOF")==0) nextToken = END_OF_FILE;
            else if (lexeme.compareTo("COMPUTE")==0) nextToken = COMPUTE;
            else if (lexeme.compareTo("EXPR")==0) nextToken = EXPR;
            else if (lexeme.compareTo("A1")==0) nextToken = ID;
            else if (lexeme.compareTo("A2")==0) nextToken = ID;
            else if (lexeme.compareTo("A3")==0) nextToken = ID;
            else if (lexeme.compareTo("ABS")==0) nextToken = FACTOR;
            else if (lexeme.compareTo("+")==0) nextToken = PLUS;
            else if (lexeme.compareTo("*")==0) nextToken = MULTIPLY;
            else if (lexeme.compareTo("(")==0) nextToken = OPEN;
            else if (lexeme.compareTo(")")==0) nextToken = CLOSE;
            else if (lexeme.compareTo("TERM")==0) nextToken = TERM;
            else if (lexeme.compareTo("FACTOR")==0) nextToken = FACTOR;
            else if (lexeme.compareTo("ID")==0) nextToken = ID;
            else if (lexeme.compareTo("FUN")==0) nextToken = FUN;