As mentioned here:
https://www.redhat.com/archives/fedora-devel-java-list/2005-March/msg00178.html
gcj will fail if asked to compile a .jar that contains a given
.class twice. At the very least it should emit a better error
message.
--
Summary: gcj failure if .jar contains same .class twice
Product: gcc
Version: 4.0.0
Status: UNCONFIRMED
Severity: normal
Priority: P2
Component: java
AssignedTo: unassigned at gcc dot gnu dot org
ReportedBy: tromey at gcc dot gnu dot org
CC: gcc-bugs at gcc dot gnu dot org,java-prs at gcc dot gnu
dot org
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=20502