How does Java run on really small devices?

Question

My understanding is that all java is run on a JVM, which requires the JVM at minimum to be present and running.

http://www.java.com/en/download/help/sysreq.xml

States the minimum requires of 64MB RAM and 58MB Hard disk space. And some OS. (Which itself cant take up space and have there own ram requirements)

But how would a small device handle to run the JVM, say on a fridge or router? Or is there a compact JVM maybe that runs on these instead? Or an older version? Or is it simply these devices have the on-board requirements, they just look small?

A related question that may be useful here: http://stackoverflow.com/questions/2735270/recommendation-for-java-vm-running-on-embedded-system — Anderson Green, Nov 21 '13 at 17:27
Probably there's a small JVM for those devices. And by *small*, I mean micro. Related: http://stackoverflow.com/q/11940169/1065197. — Luiggi Mendoza, Nov 21 '13 at 17:28

score 3 · Accepted Answer · answered Nov 21 '13 at 17:31

Oracle also provides embedded versions of the Java SE. Although I've never done any embedded projects, this is what they probably use on the small devices that you just metioned if they plan to use Java.

http://www.oracle.com/technetwork/java/embedded/downloads/javase/index.html

Although if the devices you just mentioned have less than 32MB of RAM they would be using Java ME which only requires 8MB of RAM.

How does Java run on really small devices?

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