Why is using a wild card with a Java import statement bad?

Question

It is much more convenient and cleaner to use a single statement like

import java.awt.*;

than to import a bunch of individual classes

Answer 1

Performance: No impact on performance as byte code is same. though it will lead to some compile overheads.

Compilation: on my personal machine, Compiling a blank class without importing anything takes 100 ms but same class when import java.* takes 170 ms.