sentences:  IcedTea 1.x and 2.x can compile OpenJDK using GNU Classpath-based solutions such as GCJ and optionally bootstraps itself using the HotSpot Java Virtual Machine and the javac Java compiler it just built.For now, building IcedTea 3.x requires using IcedTea 2.x or 3.x, or an OpenJDK 7 or 8 build from another source.Cross-architecture ports of HotSpot (OpenJDK's Virtual Machine) are difficult, because the code contains much assembly language, in addition to the C++ core.