Check a jar to make sure all the javac -target versions of
the class files are what you expect.
to use:
java.exe -jar jarcheck.jar   jartotocheck.jar 1.1 1.8
where jartocheck.jar is the name of jar to check.
It will check all the class files in it.
In this example:
1.1 is the lowest acceptable target version number.
1.8 is the highest acceptable target version number.
Returns errorlevel 0 = all ok
                   1 = one or more class files bad
                   2 = jar unreadable or syntax error
Errors are directory to System.err and messages about
correct entries go to System.out.
Currently, only version numbers 1.0...1.8 are supported.  The program does
not currently test minor version numbers.
Why would you use this utility? To make sure that a jar
intended to run under an old 1.1 JVM contains no classes
accidentally compiled with javac -target 1.5.  Passing this
test does not guarantee the jar will work on an old JVM. The
jar still might use methods not bundled with old JVMs. This
should catch however, classes normally compiled with target
1.1 that were accidentally compiled with 1.5 as a side
effect of compiling some 1.5 class.
You can download it from
http://mindprod.com/products1.html#JARLOOK
To install, Extract the zip download with WinZip, available from
http://www.winzip.com (or similar unzip utility) into any
directory you please, often C:\ -- ticking off the "user
folder names" option. To run as an application, type:
java.exe -jar C:\com\mindprod\jarcheck\jarcheck.jar
adjusting as necessary to account for where the jar file is.
Don't confuse jarcheck with a similar simpler CMP utility called
jarlook.
Why the coffee bean in a jar icon?  This is Sun's logo to
represent Java in a jar file.