A JIT compiler simply compiles byte code as it executes. JIT refers to the fact that it compiles byte code only when it's ready to be executed -- just in time, in other words. JIT compilers are very powerful because only code that actually executes is compiled; methods that are executed frequently can be retrieved from the native method cache at execution time and executed on the fly. There is one big issue with JIT compilers: once a method has been compiled, it loses the power of portability, because it has been compiled to the native code of the hardware and consequently isn't portable any longer.
By the way,the Java HotSpot performance engine is Sun's next-generation compilation technology that compiles only performance-critical code. The latest version of HotSpot provides both client- and server-side solutions.
HotSpot has a dynamic compiler, but it differs from a JIT in that it uses heuristics to determine which section of the code should be executed and is more aggressive when optimizing the selected code than a typical JIT compiler. Java, java, J2SE, j2se, J2EE, j2ee, J2ME, j2me, ejb, ejb3, JBOSS, jboss, spring, hibernate, jdo, struts, webwork, ajax, AJAX, mysql, MySQL, Oracle, Weblogic, Websphere, scjp, scjd Short for just-in-time compiler, a code generator that converts Java bytecode into machine language instructions. Some Java Virtual Machines (VMs), including the VM in the Netscape Navigator browser, include a JIT in addition to a Java interpreter. Java pro
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