However, several independent "partial" reimplementations of the Java platform had been created, many of them by the open-source community, such as the GNU Compiler for Java (GCJ). Sun never filed lawsuits against any of the open source "clone projects". GCJ notably caused a bad user experience for Java on free software supporting distributions such as Fedora and Ubuntu which shipped GCJ at the time as their Java implementation. How to replace GCJ with the Sun JDK was a frequently asked question by users, because GCJ was an incomplete implementation, incompatible and buggy.