Package ecj appears to be using Java generics, but generates class files in format older than 49.0, which corresponds to J2SE 5.0, in which generics were introduced. Please update this package to generate classes in format 49.0 or above. This corresponds to -target 1.5 option of javac (or ecj). For more information, see bug #842394
I've reviewed ecj package in detail and I believe this is a false positive. There are two very good reasons for this false positive. First, in the sources there are java files which use generics. However, these are files not needed for the package and are removed during rpm build (they are never compiled; I didn't dig too deep but I believe these have mainly to do with integrating this with eclipse itself, but this package exists only to provide ecj executable separately from eclipse). Second, in the files remaining there are quite a bit of references in the comments to generics, documenting the compiler implementation. I find it interesting that ecj is able to compile java code with generics, without using them in its own source code. Since this is false positive, I'm closing this bug.