In HotSpot JVMs (Sun JDK 1.2 and later), things got a lot better -- the Sun JDKs moved to a generational collector. Because a copying collector is used for the young generation, the free space in the heap is always contiguous so that allocation of a new object from the heap can be done through a simple pointer addition, as shown in Listing 1. This makes object allocation in Java applications significantly cheaper than it is in C, a possibility that many developers at first have difficulty imagining. Similarly, because copying collectors do not visit dead objects, a heap with a large number of temporary objects, which is a common situation in Java applications, costs very little to collect; simply trace and copy the live objects to a survivor space and reclaim the entire heap in one fell swoop. No free lists, no block coalescing, no compacting -- just wipe the heap clean and start over. So both allocation and deallocation costs per object went way down in JDK 1.2.