import *
*General import is to import all the classes in the classpath in a jar package. import java.util .*;
is to import all the classes under java/util/. If there is a common directory under util. The classes in the common directory are not imported.
Generally, when writing programs, * is not written; when those classes are used, those classes are imported. This is slightly faster. So don't do a full search. Directly locate the location of the class.