An optional parameter, indicating whether the freshly added content should be followed by a 'commit' (this is, by the way, a very good way to optimize batch-indexings of content)
In brief, this methods acts as follows :
Checks whether the content object should be indexed or not, according to the list of excluded content classes (settings : [IndexExclude])
Retrieval of the objects's metadata and creation of names and values for the associated Solr fields
Retrieval of the node's metadata and creation of names and values for the associated Solr fields
Retrieval of the object attributes' content, for each language, and creation of names and values for the associated Solr fields
Push of the collected data to Solr's index, in single or multi-core mode, depending on the settings
Final commit, conditioned by the second, optional parameter of the addObject method
Note : since eZ Find 2.2, it is possible to use language-specific 'cores' (/extension/ezfind/java/solr.multicore), allowing for having per-language indexes and configuration files (spellings.txt, synonmys.txt, stopwords.txt, etc.).