The Java Virtual Machine interprets and executes the bytecode instructions in the *.class file. On Sun's JVM, (part of) the bytecode instructions are translated on the fly to native machine instructions for the processor that the JVM is running on, by the HotSpotjust-in-time compiler. This makes Java run very fast.
(Click on the links for more info). [ May 14, 2008: Message edited by: Jesper Young ]