question: public final void addCategory ( String category ) { if ( mCategories == null ) mCategories = new ArrayList < String > ( ) ; if ( ! mCategories . contains ( category ) ) { mCategories . add ( category . intern ( ) ) ; } }
target:  Add a new Intent category to match against.  The semantics of categories is the opposite of actions -- an Intent includes the categories that it requires, all of which must be included in the filter in order to match.  In other words, adding a category to the filter has no impact on matching unless that category is specified in the intent.