Why The Green Thread model is Implemented in java by SunMicrosystems?

Why The Green Thread model is Implemented in java by SunMicrosystems?
the thread scheduling is managed by virtual machine ie JVM. as compare to the Native Thread model, the thread scheduling is managed by the OS.In Green Theard Model the Green threads supports multithreaded environment without depending on native Operating System . The Green Threads run code in user space those are manages and schedules threads; SunMicrosystem wrote green thread model to provide the Freature of green threads can be used in java.So Java can work in environment that do not have native thread support.

In the Green Thread model, the OS doesn't know anything about the threads used in the JVM. It's up to the JVM that how to handle all the details.

Green threads can't take advantage of multiple CPUs, but they have the advantage of lighter weight for context switching.