http://java.sun.com/j2se/1.4.2/docs/guide/versioning/spec/versioningTOC.html
That should give you a lot of information 
It’s actually not crystal clear if my suggestion will actually work (information provided be the link seems to contradict the api documentation of isCompatibleWith??)
EDIT: I believe the syntax of the version string is
.[.<“bugfix”>]
i.e. microsoft vm isCompatibleWith(“1.1”) should return true - but
isCompatibleWith(“1.1.9”) should return false (replace 9 with the actual latest bug fix number of the ms vm +1 )
And the current (1.4.2) should return true when given isCompatibleWith(“1.4”) (or 1.4.2, 1.4.1, 1.3.1 etc etc 