cannot compile jar with eclipse, used both 1.6 and 1.7 versions. please help

[GoogleCodeExporter]

What steps will reproduce the problem?
1. install eclipse sdk
2. try compile with 1.7 or 1.6
3. ERROR: Unsupported major.minor version 51.0

i want to add any window support but i cannot compile because "Unsupported 
major.minor version 51.0" error. have not found solution in net.

i also compiled separate classes and inserted win.windowEnvirontent.class to 
existing working .jar
same error

Please can someone post instruction on how to compile working shimeji ee jar? 
or one needs to be java profy just to compile working .jar?
huge thanks in advance! =*^_^*=

Original issue reported on code.google.com by whyieyes...@gmail.com on 10 Aug 2014 at 12:19

[GoogleCodeExporter]

OK FUCK ECLIPSE 4 hours wasted!
just get netbeans, setup it EASILY, compile jar for 1.6/ open jar with 7zip 
extract win.WindowsEnvironment.class
open original ee jar
replace WindowsEnvironment.class to it

run original jar (dont forget to add window.txt

ENJOY ^_^

Original comment by whyieyes...@gmail.com on 10 Aug 2014 at 2:21