In theory yes. In practice 99.99% of mainstream Java developers will run their code on Oracle's JVM.
- Real time deployment scenarios
- J2EE containers, which tend to work best with the respective vendor JVM
- factory control JVMs
- car infotaiment JVMs
- smart card JVMs
- Compilation to native code
- Android
- Embedded deployments like MicroEJ
- Commercial UNIX systems
- Mainframes
- ...