It may not be needed. The author may just have done it because they could, and thought it was neat. But the potential reasons for wanting it is that now the ru

It may not be needed. The author may just have done it because they could, and thought it was neat. But the potential reasons for wanting it is that now the runtime is the JVM, MRI (Matz's Ruby interpreter). JRuby accomplishes using the JVM as the runtime for Ruby by reimplementing the Ruby runtime in Java. This is a different approach, one in which Ruby code is compiled to Java code, rather than using Java runtime interpret Ruby code.