You won't be able to type them in Java, at least not now; however it would allow new JVM languages to do it. You could also do fibers on the JVM before, but the

You won't be able to type them in Java, at least not now; however it would allow new JVM languages to do it. You could also do fibers on the JVM before, but they didn't have access to the actual JVM stack. That kind of limits their usefulness and performance.