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Just In Time compiler

chander shivdasani
Ranch Hand

Joined: Oct 09, 2007
Posts: 206


I have this confusion with Java Compiling and Interpreting process.

Java code is compiled and is converted into bytecode
Then this bytecode is interpreted using interpreters.

My question is, where does JIT comes into picture in this scenario. How does the JIT process differ from the standard interpreters shipped with JVM?
Any links, or references to resources will be appreciated.


Enjoy, Chander
SCJP 5, Oracle Certified PL/SQL Developer
Ernest Friedman-Hill
author and iconoclast

Joined: Jul 08, 2003
Posts: 24199

JVMs haven't operated as pure interpreters in many years. From your description, take out "intepreted by interpreters" and put in "dynamically compiled into native machine code" instead. A just-in-time compiler does the final step of compilation -- machine code generation -- right before execution ("just in time to be executed"), inside the running virtual machine. Sun's HotSpot JVM goes one further by analyzing the code and concentrating on compiling and optimizing the performance-critical parts.

[Jess in Action][AskingGoodQuestions]
David Newton

Joined: Sep 29, 2008
Posts: 12617

And it's *really* good. I wish Smalltalk VMs had gotten the same love (we're getting there!)
I agree. Here's the link:
subject: Just In Time compiler
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