We need more details. What is the command invoked to "build" the JAR file? Which version of Java do you have on the Linux box? This error normally comes up when you try to compile code containing generics using pre 1.5 source level.
to build the jar file I'm invoking those commands :
javac compute/Compute.java compute/Task.java ( after invoking this the error appears because I used in the code the template <T> )
jar cvf compute.jar compute/*.class
the version .. when I run sudo update-alternatives --config java
it says : java-6-openjdk