Jan 25, 2018

Java 9: JDK without subfolder JRE

In older JDK releases the directory structure was:
With JEP 220 the jre folder was removed.

A JDK image no longer contains a jre subdirectory, as noted above. Existing code that assumes the existence of that directory might not work correctly.
But this does not mean that there is no JRE any more. You can still download the JRE. There are some minor changes to the JRE like:
The bin directory in a JRE image contains a few commands that were previously found only in JDK images, namely appletvieweridlj,jrunscript, and jstatd. As with the previous item, these changes are a consequence of the way in which components that contain both APIs and tools were modularized.
For both version the files rt.jar, tools.jar and dt.jar are removed:
JDK and JRE images no longer contain the files lib/rt.jar,lib/tools.jarlib/dt.jar, and other internal JAR files, as noted above. Existing code that assumes the existence of these files might not work correctly.
But this should not be a problem:
Class and resource files previously found in lib/dt.jar and visible only when that file was added to the class path are now visible via the bootstrap class loader and present in both the JRE and the JDK. 
Everyone who delivers Java applications should read  JEP 220 and check, what has to be changed...

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