This article provides non-exhaustive lists of Java SE Java virtual machines (JVMs).
Note that Java EE runs on the standard Java SE JVM but that some vendors specialize in providing a modified JVM optimized for Java EE applications.
Much Java development work takes place on Windows, Solaris, Linux, and FreeBSD, primarily with the Oracle JVMs.
The primary reference Java VM implementation is HotSpot, produced by Oracle Corporation and many other big and medium-sized companies (e.g. IBM, Redhat, Microsoft, Azul, SAP).
Some JVM's are intended to run without an underlying OS.