The class-based garbage collection approach is to improve the efficiency of the runtime environment for server applications. The class-based garbage collection algorithm is intended to reduce the overhead of dynamic object creation through an object-reuse technology, and the unique techniques of thread cache and lease protocol etc. can further reduce the pause time of the server applications and provide them better smoothness and good memory usage. The virtual machines run on top of the class-based garbage collector can be implemented to support fine grade parallelism between the mutator threads and the garbage collection threads.