Building error using JDK 7

[GoogleCodeExporter]

What steps will reproduce the problem?
1. Download clean 3.0.0-SNAPSHOT version from SVN
2. mvn -Dmaven.test.skip=true
3.  [proguard] Error: Can't read [C:\Program 
Files\Java\jdk1.7.0\jre\lib\rt.jar] (Can't process class 
[com/oracle/net/Sdp$1.class] (Unsupported version number [51.0] for class 
format))

What is the expected output? What do you see instead?

Build success

What version of the product are you using? 

3.0.0-SNAPSHOT

On what operating system?

JDK 7 on Windows 7

Please provide any additional information below.

It looks like it is a problem in proguard 4.2 which doesn't support Java 7 
class files.

 [proguard] ProGuard, version 4.2
 [proguard] Reading program jar [C:\toro\microemu\microemu-cldc\target\microemu-cldc-3.0.0-SNAPSHOT.jar] (filtered)
 [proguard] Reading library jar [C:\Program Files\Java\jdk1.7.0\jre\lib\rt.jar]
 [proguard] Error: Can't read [C:\Program Files\Java\jdk1.7.0\jre\lib\rt.jar] (Can't process class [com/oracle/net/Sdp$1.class] (Unsupported version number [51.0] for class format))

Original issue reported on code.google.com by j...@toro-asia.com on 18 Oct 2011 at 8:50

[GoogleCodeExporter]

The latest version of ProGuard (4.6) doesn't support Java 7 either. We have to 
wait until 4.7 is released, at the moment is in beta stage.

Original comment by bar...@gmail.com on 1 Nov 2011 at 1:06

[GoogleCodeExporter]

[deleted comment]

[GoogleCodeExporter]

i see the same issue but i have a larger version number, and also JSK 8, so the 
issue is similar to the one stated here :

http://stackoverflow.com/questions/22670059/error-proguard-unsupported-class-ver
sion-number

Original comment by ahm3d.a...@gmail.com on 25 Nov 2014 at 2:48