CompressedOops - HotSpot Internals for OpenJDK - wikis.sun.comCompressed oops in the Hotspot JVM What's an oop, and why should they be compressed? An "oop", or "ordinary object pointer" in HotSpot parlance is a managed pointer to an object. It is normally the same size as a native machine pointer, which means 64 bits on an LP64 system. On an ILP32 system, there is a maximum heap size of somewhat less than 4Gb, which is not enough for many applications. On an
