What is HotSpot?

I just heard of the HotSp开发者_C百科ot JVM, as opposed to the Oracle JRockik JVM. What is Hotspot? Is this old the Sun JVM, or something else?

HotSpot is the shipped Sun JVM which has support for just-in-time compilation of heavily used sections of code.

For all practical purposes, it is the "Sun JVM" or now the "Oracle JVM". Note that this is the same JVM which was open sourced, so it is also the "OpenJDK JVM".

Way back when, Sun did release a non-JIT capable JVM, but that's long enough ago that the odds of encountering it are minuscule.

AFAIK, its the old Sun JVM which is now part of OpenJDK and therefor a reference for many other implementations.

Oracle's JVM is called HotSpot.

Java applications are compiled into bytecode using javac. During application runtime, the JVM loads class files into memory and analyzes the program’s performance for hot spots; hence the name “HotSpot JVM”. The just-in-time (JIT) compiler compiles parts of the application which are executed repeatedly into native machine code. JIT compilation, however, requires processor time and memory which affects the startup time of the application.

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