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A question about JIT(just-in-time)

Michael Keisu
Ranch Hand

Joined: Oct 08, 2009
Posts: 30
So I am taking notes in order to better learn Java, however I have come across something which confused me a bit(JIT). I'm not sure if it is a beginner subject exactly as the book
I used for the Java course I took didn't mention it, but another one I'm on did, and this is how I interpreted it, in my own words:

When running a program the Java Virtual Machine interprets java bytecode in combination with using the just-in-time compiler to translate
the heavy/frequently used instructions/java bytecode into machine code at runtime, to achieve better speed. In the early Java days,
when JIT didn't exist, Java programs ran more slowly. Of course, that also had to do with computers being slower.


So I'm basically asking if I got it right? What more is there to it? I would like to learn all the details

thanks in advance.
Ulf Dittmer
Marshal

Joined: Mar 22, 2005
Posts: 41586
    
  54
Welcome to JavaRanch.

Basically, your interpretation is correct. JITs have improved a LOT since they first appeared, though, so that's another factor of the speedup. Search for "HotSpot" to find information about Sun's runtime environment and JIT.


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Michael Keisu
Ranch Hand

Joined: Oct 08, 2009
Posts: 30
Thank you

I think I got pointed in the right direciton
this is what I found -> http://java.sun.com/products/hotspot/docs/whitepaper/Java_Hotspot_v1.4.1/Java_HSpot_WP_v1.4.1_1002_4.html
I believe that's the latest on the subject
Campbell Ritchie
Sheriff

Joined: Oct 13, 2005
Posts: 38429
    
  23
No, that page is over 6 years old. Try here for something more recent.
 
It is sorta covered in the JavaRanch Style Guide.
 
subject: A question about JIT(just-in-time)