posted 21 years ago
During runtime you'll notice no difference whatsoever (the .class file wouldn't differ either) but during compile time the 'import java.util.*' makes the compiler drag in *all* classes from that package, ready to be scrutinized and inspected when needed, so some performance degradation would be noticable during compilation.
If you just need one or a couple of classes from a package it is considered 'well mannered' to explicitly import them instead of importing the entire package.
kind regards