Difference between 'java' and 'libjvm.so' (Linux) or 'jvm.dll' (Windows)?

Question

What are the differences in starting an application through the plain java command, against directly invoking the JVM through libjvm.so in Linux or jvm.dll in Windows ?

Recently I saw on a forum that starting eclipse using the dll or .so file will give better performance. I would like to get to know how this happens.

Thanks.

Answer 1

Typically folks build against jvm.dll if they want to wrap their own functionality around a Java core, where sometimes it's hard to do things that look "native" from Java. A good example is indeed Eclipse, where they want to pop up a splash screen and do some other actions before starting up. For other products, it's that Java is only a small part of their workload (eg: large C++ app that needs to bridge into Java at some point).

From a performance perspective, it's irrelevant. It's all about how you want the "fit and finish" for things like Eclipse.

Answer 2

The link discusses Eclipse start-up; it is likely that this is faster because, by using the -vm argument to specify the JRE, the Eclipse executable doesn't have to search the system for an appropriate JRE to launch (which would incur disk I/O and possibly involve detecting the version of the JRE). You aren't speeding up Java, you're speeding up the native launcher.