This list of compatibility issues is by no means complete.
gcj implements the JDK 1.2 language. It supports inner classes
and the new 1.4 assert keyword. It does not yet support the Java 2
strictfp keyword (it recognizes the keyword but ignores it).
libgcj is largely compatible with the JDK 1.2 libraries.
However, libgcj is missing many packages, most notably
java.awt. There are also individual missing classes and methods.
We currently do not have a list showing differences between
libgcj and the Java 2 platform.
libgcj implementation of a method or class differs
from the JDK implementation. This is not always a bug. Still, if it
affects you, it probably makes sense to report it so that we can discuss
the appropriate response.
gcj does not currently allow for piecemeal replacement of
components within libgcj. Unfortunately, programmers often want
to use newer versions of certain packages, such as those provided by
the Apache Software Foundation's Jakarta project. This has forced us
to place the org.w3c.dom and org.xml.sax packages into
their own libraries, separate from libgcj. If you intend to
use these classes, you must link them explicitly with
-l-org-w3c-dom and -l-org-xml-sax. Future versions of
gcj may not have this restriction.