There is the nailgun project (http://www.martiansoftware.com/nailgun/ http://www.martiansoftware.com/nailgun/) which seems to initialize a JVM in the background

There is the nailgun project (http://www.martiansoftware.com/nailgun/ http://www.martiansoftware.com/nailgun/) which seems to initialize a JVM in the background so that tasks can execute more quickly, but it's not being maintained.