3 ms·

This is IBM's formerly-proprietary J9 JVM, which I believe was developed entirely from scratch, independently of Sun's HotSpot JVM. J9 actually has its roots i

This is IBM's formerly-proprietary J9 JVM, which I believe was developed entirely from scratch, independently of Sun's HotSpot JVM. J9 actually has its roots in an earlier Smalltalk VM (VisualAge Smalltalk, I think). The source copyrights go back to 1991. Eclipse, of course, was what IBM started after abandoning VisualAge. It's not a JDK/JRE. J9 must be combined with OpenJDK to be able to run apps.

merb 9y ago
> It's not a JDK/JRE. J9 must be combined with OpenJDK to be able to run apps. well yes and no. if you don't use anything from the standard class library (that's impossible) than not. what I also guess is that you need a java compiler, since it reads that it uses a ibm created "rom file" that comes from java bytecode. what the most interesting thing about that vm is, is a shared class cache. which is like a *.so file, if one program loads a library and the library is already in memory another program won't add additional memory to the computer, this is a huge win, especially for memory hungry java applications (this already speeds startup extremly)
- emmelaich 9y ago
  They already have a compiler, ECJ, which is included in Eclipse and Tomcat among other things.
  - oblio 9y ago
    ECJ is in Tomcat? What for?
    - emmelaich 9y ago
      Compiling Java :-) To be more precise, a compiler is required for JSP, which is a mixture of html and java that is compiled to servlets. Theoretically you can compile them ahead of time (before deployment) but as far as I can tell no-one does.
      - solarengineer 9y ago
        Those who want to provide only class files and no jsp code use the JSP pre-compilation approach. The JSP folks get compiled to Java servlet byte code the same as at runtime.
  - merb 9y ago
    does ecj support indy and newer bytecode? I do not think so, but I guess openj9 already supports java 9 bytecode I'm not sure about the actual bytecode version I guess it was 52 on java 8 but I'm not totally sure about it. I mean ecj is also not included in openj9, so if you want to strip out any openjdk dependency one would need at least a really basic class lib and a compiler (either ecj or anything else), (but I also think it hears that openj9 includes a compiler https://www.youtube.com/watch?v=96XoG6xcnys https://www.youtube.com/watch?v=96XoG6xcnys at the end he only says that they use the class library from openjdk, but he does not say if anything else and it also looks like it only uses that).
dlandis 9y ago
> J9 must be combined with OpenJDK to be able to run apps. No IBM has its own full JDK that you can download, but the rest of it other than the JVM is not being open sourced at this time. That's my understanding at least.
- mstoodle 9y ago
  The IBM SDK for Java is based on OpenJDK, just like most (not all) other Java releases that are out there. IBM does not have "its own full JDK".

merb 9y ago

> It's not a JDK/JRE. J9 must be combined with OpenJDK to be able to run apps. well yes and no. if you don't use anything from the standard class library (that's impossible) than not. what I also guess is that you need a java compiler, since it reads that it uses a ibm created "rom file" that comes from java bytecode. what the most interesting thing about that vm is, is a shared class cache. which is like a *.so file, if one program loads a library and the library is already in memory another program won't add additional memory to the computer, this is a huge win, especially for memory hungry java applications (this already speeds startup extremly)

emmelaich 9y ago
They already have a compiler, ECJ, which is included in Eclipse and Tomcat among other things.
- oblio 9y ago
  ECJ is in Tomcat? What for?
  - emmelaich 9y ago
    Compiling Java :-) To be more precise, a compiler is required for JSP, which is a mixture of html and java that is compiled to servlets. Theoretically you can compile them ahead of time (before deployment) but as far as I can tell no-one does.
    - solarengineer 9y ago
      Those who want to provide only class files and no jsp code use the JSP pre-compilation approach. The JSP folks get compiled to Java servlet byte code the same as at runtime.
- merb 9y ago
  does ecj support indy and newer bytecode? I do not think so, but I guess openj9 already supports java 9 bytecode I'm not sure about the actual bytecode version I guess it was 52 on java 8 but I'm not totally sure about it. I mean ecj is also not included in openj9, so if you want to strip out any openjdk dependency one would need at least a really basic class lib and a compiler (either ecj or anything else), (but I also think it hears that openj9 includes a compiler https://www.youtube.com/watch?v=96XoG6xcnys https://www.youtube.com/watch?v=96XoG6xcnys at the end he only says that they use the class library from openjdk, but he does not say if anything else and it also looks like it only uses that).

dlandis 9y ago

> J9 must be combined with OpenJDK to be able to run apps. No IBM has its own full JDK that you can download, but the rest of it other than the JVM is not being open sourced at this time. That's my understanding at least.

mstoodle 9y ago
The IBM SDK for Java is based on OpenJDK, just like most (not all) other Java releases that are out there. IBM does not have "its own full JDK".