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{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"Unloading rJava and/or restarting JVM","articleBody":"[Repost from [this SO question](https://stackoverflow.com/questions/24337383/unloading-rjava-and-or-restarting-jvm)]. \n\nI would like to use `rJava` in combination with `mcparallel` but obviously [the JVM cannot be forked](https://stat.ethz.ch/pipermail/r-devel/2013-November/067960.html). Therefore a separate JVM instance needs to be initiated for each child process, e.g:\n\n```\nlibrary(rJava)\nlibrary(parallel)\nmyfile \u003c-  system.file(\"tests\", \"test_import.xlsx\", package = \"xlsx\")\n\n#This works:\nmccollect(mcparallel({\n  #Automatically initiates JVM in child\n  xlsx::read.xlsx(myfile, 1)\n}))\n```\n\nHowever the problem in my case is that the JVM has already been initiated in the (main) parent process as well. This makes it impossible to use `rJava` in the child process:\n\n```\n#init JVM in parent\n.jinit()\n\n#Doesn't work anymore\nmccollect(mcparallel({\n  xlsx::read.xlsx(myfile, 1)\n}))\n```\n\n So what I really need is a way to shutdown/kill and restart the JVM in the child process. Simply  `detach(\"package:rJava\", unload = TRUE)` doesn't seem to do the trick. The `force.init` parameter doesn't seem to result in a restart either:\n\n```\n#Also doesn't work:\n.jinit()\nmccollect(mcparallel({\n  .jinit(force.init = TRUE)\n  xlsx::read.xlsx(myfile, 1)\n}))\n```\n\nIs there some way I can forcefully shutdown/kill the JVM in order to reinitiate it in the child process?\n","author":{"url":"https://github.com/jeroen","@type":"Person","name":"jeroen"},"datePublished":"2014-08-10T08:01:31.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":19},"url":"https://github.com/25/rJava/issues/25"}