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jre & jvm

sreejith panampilly
Ranch Hand

Joined: Jun 15, 2006
Posts: 49
what is the difference between jre and jvm ?
Ernest Friedman-Hill
author and iconoclast
Marshal

Joined: Jul 08, 2003
Posts: 24183
    
  34

A JVM (Java Virtual Machine) is an imaginary (theoretical) machine that executes Java bytecodes.

A JRE (Java Runtime Environment) is a software implementation of a JVM and all the standard Java libraries, and other bits and pieces that are needed to make the thing actually work.

A JDK (Java Developer's Kit) or J2SDK (Java 2 Software Developer's Kit) are two different names for the same thing: a JRE plus tools like the Java compiler, debugger, and other things needed for basic Java development.


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Dave Chawan
Greenhorn

Joined: Jun 29, 2006
Posts: 7
I have different versions of jdk installed on my pc and there are different jre folders. Is correct the classpath determines which "environment" (jre) to execute my java programs?

And some of the names in jdk bin folder and jre bin folder are the same, like java.exe and rmiregistry.exe. Are they actually the same things? Why having this duplication?

Thanks,
Dave
mara thamizhan
Ranch Hand

Joined: Jul 05, 2006
Posts: 74
hi all,
I have a simple doubt!

We are importing packages like java.io.*; in our classes !

Can we see the classes,along with all their members & its definitions, which are there in the respective packages like java.io package etc.

cheers,
Bye!
Campbell Ritchie
Sheriff

Joined: Oct 13, 2005
Posts: 38334
    
  23
Somebody else has asked the same question today; I hope it wasn't you asking twice.
Go to the API website, which you need to become familiar with, and click on the name of a package (if you have the frames view on, the list of packages seems to stay in the upper left frame).

If you want to see the actual text of the classes, you have to join the Sun Developers' Network.
Timothy Frey
Ranch Hand

Joined: Jul 22, 2006
Posts: 56
Aren't the source files for the Java libraries including with the JDK in the src.zip file?
Guy Allard
Ranch Hand

Joined: Nov 24, 2000
Posts: 776
Originally posted by Timothy Frey:
Aren't the source files for the Java libraries including with the JDK in the src.zip file?


That zip has all the source code for the functionality that is implemented in the Java language.

On any platform there will be native code, packaged as .dll or .so files.

That code is (AFAIK) in C, and the C sources are not provided.

Guy
Dave Chawan
Greenhorn

Joined: Jun 29, 2006
Posts: 7
Could anyone answer my question that I posted earlier under this topic?

I have different versions of jdk installed on my pc and there are different jre folders. Is correct the classpath determines which "environment" (jre) to execute my java programs?

And some of the names in jdk bin folder and jre bin folder are the same, like java.exe and rmiregistry.exe. Are they actually the same things? Why having this duplication?

Thanks,
Dave
 
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