As per the specification of Runtime.Version:

 A version string, $VSTR, is a version number $VNUM, as described above, optionally followed by pre-release and build information, in one of the following formats:

       1. $VNUM(-$PRE)?\+$BUILD(-$OPT)?
       2. $VNUM-$PRE(-$OPT)?
       3. $VNUM(+-$OPT)?
     
So an example of "10--ea" does not confirm to any of the above regex's.

10--ea does not have build component hence it cannot fit in regex 1
10--ea does not have pre component hence it cannot fit in regex 2
10--ea does not have + sign hence it cannot fit in regex 3

So we expect IllegalArgumentException when such string is passed to Version#parse method. This is mentioned in the specification of parse method as below:

IllegalArgumentException - If the given string cannot be interpreted as a valid version

However when i try to parse the string below in jshell , string is parsed fine and no exception is thrown.

jshell> Runtime.Version.parse("10--ea")
$6 ==> 10+--ea

Furthermore , as you can see above, the input is tampered and a "+" is added to it to fit it to regex 3

One more example:
jshell> Runtime.Version.parse("10.0.0.1---ea")
$5 ==> 10.0.0.1+---ea

jshell> Runtime.Version.parse("10.0.1--")
$5 ==> 10.0.1+--