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Why is Java JRE in a jar file ?

4 replies [Last post]
Joined: 2006-01-22

i hope i am wrong but doesn't having the jre in a jar file mean that you already have to have java installed to install the new java runtime ?

that would be kind of silly, if i had to tell my clients to first install java 1.5, then download java 1.6 and use java 1.5 to install 1.6 ??

maybe someone can enlighten me...



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Joined: 2003-06-18

thanks mike, thats exactly what i wanted to know

Joined: 2004-09-03

Mike is correct. But there are non-jar (*.exe) distributions of the JDK 6 at too, so there are ways to install a JDK without having a JDK. We often use jar files as a way to put a simple wrapper around the bundle, enforcing the license viewing, and/or in providing a non-formal install bundle. Consider it a smart zip file, hopefully we can convert what we are now using to something more open like in the future.

And I'm pretty sure JDK 1.5 isn't necessary to explode these jar bundles, JDK 1.4.2 should work fine, or at least that was our intent.

But the simple answer is 'yes' you need a JDK to explode any of these JDK 6 jar files.

Hope this helps explain things.


Joined: 2006-01-06

I think you are referring to the Java 6 JDK/JRE self-extracting JAR files, i.e. the installers that are only available on If I am correct, then yes, you do need to have a previous version of Java installed in order to install these.

However, these files are:

A) not part of a released product. These are intended to be used by developers and IT staff that want to prepare for running their product(s) with the newest code before its general availability release.

B) not the preferred install method. These install a private JDK/JRE that is not fully registered with the system. (For more information on public/private installs, see

C) not available to the general public after GA/FCS release.

If you have customers that are beta testing you product(s), which are based on the pre-release of Java 6, you need to ask them to use only the non-self-extracting installer, or instruct them how to use the self-extracting installer. This is just a consequence of working with pre-released code. After release you can be sure that your customers will only see the safe, easy to install versions.


Joined: 2005-08-10

More then likely what your seeing is the java runtime classes in the jar, while the native code is still installed via a normal installer.