From the JDK 6 adoption guide:
The ObjectName functionality has been extended in Java SE 6 such that you can put a wildcard (* and/or ?) anywhere in a value, e.g., key=a*b as well as key=*. The asterisk matches any sequence of zero or more characters, while the question mark matches any single character.

The tests using the following BAD_KEYVALS no longer throw the expected MalformedObjectNameException when running with JDK 6
// strings containing illegal chars to use in key or value positions
public static final String[] BAD_KEYVALS = {
"som?thing", // cannot contain pattern chars
"som*thing", // cannot contain pattern chars
};
AssertionFailedError: invalid object name: domain:key1=som*thing
invalid object name: domain:key1=som?thing