Refactor source code

[ouertani]

In relation to #3 update source code to java 8 news features :
No abstract class, Lambdas ..

[puredanger]

I don't think we have any desire to lose older Java compatibility yet.

[ouertani]

@puredanger can be as separate brunch for full 1.8 ?

<configuration>
          <source>1.8</source>
      <target>1.8</target>
      <compilerArgument>-Xlint:unchecked,rawtypes</compilerArgument>
</configuration>

[Jiehong]

7 years later, I think that's now acceptable, if this was still maintained ;)