make/java/sun_nio/Makefile compiles with -Xlint:serial -Werror and so fails when compiling with JAVAC_MAX_WARNINGS=true due to the deprecated sun.io converters. In addition, there are several unnecessary casts and raw type warnings that can be removed from this code. See this discussion:

http://mail.openjdk.java.net/pipermail/nio-dev/2010-January/000887.html