Java 8 method references: provide a Supplier capable of supplying a parameterized result

Sure.

.orElseThrow(() -> new MyException(someArgument))

It appears that you can throw only RuntimeException from the method orElseThrow. Otherwise you will get an error message like MyException cannot be converted to java.lang.RuntimeException

Update:- This was an issue with an older version of JDK. I don't see this issue with the latest versions.

optionalUsers.orElseThrow(() -> new UsernameNotFoundException("Username not found"));