JamVM
JamVM is an open-source Java Virtual Machine (JVM) developed to be extremely small compared with other virtual machines (VMs) while conforming to the Java virtual machine specification version 2 (blue book). JamVM can be configured to use the GNU Classpath or the OpenJDK Java class library and recent versions support object finalization, Soft/Weak/Phantom References, the Java Native Interface (JNI) and the Reflection API. The compacting garbage collector can run either synchronously or asynchronously within its own thread.