Jikes RVM (Research Virtual Machine) provides a flexible open testbed to prototype virtual machine technologies and experiment with a large variety of design alternatives. Jikes RVM runs on many platforms and advances the state-of-the-art of virtual machine technologies for dynamic compilation, adaptive optimization, garbage collection, thread scheduling, and synchronization. It is self-hosted, i.e. its Java code runs on itself without requiring a second virtual machine. Most other virtual machines for the Java platform are written in native code (typically C or C++). A Java implementation provides ease of portability and a seamless integration of virtual machine and application resources such as objects, threads, and operating-system interfaces.