1. A method for incrementally unloading classes using a region-based garbage collector, the method comprising: maintaining, by at least one processor, a remembered set for a class set, the remembered set indicating whether instances of the class set are contained in one or more regions in memory, and in which regions in memory the instances are contained, wherein the remembered set of each class set is implemented using one of a plurality of possible representations, the possible representations comprising: (1) an “immediate” representation storing pointers to specific regions in memory where instances of the class set are contained; and (2) a “bit vector” representation comprising a bit for each region in memory that indicates whether at least one instance of the class set is contained in the corresponding region; upon performing an incremental garbage collection process for a subset of the regions in memory, examining the remembered set to determine whether the class set includes instances in regions outside of the subset; and identifying the class set as “live” if the remembered set indicates that the class set includes instances in regions outside of the subset.