See thread
http://mail.openjdk.java.net/pipermail/jdk6-dev/2010-November/002105.html

Summary:

"This test check, if the temporary file containing font is properly
deleted when JVM finishes. The check is based on counting of files in
temporary dir - if temporary font file is not deleted, the number of
files before and after running the test differs.

BUT JVM also creates hsperfdata_* subdirectory so the check described
above always fails (presence of this subdirectory add +1 to number of
files). I've added simple filter to resolve this issue. Another option
is to disable the hsperfdata_* creation at all."