Import package with .* in jsp

Question

If i want to use HashMap in jsp page i need to have HashMap of util package in import statment in
page directive.
What is difference in Using
a) <%@ page import="java.util.HashMap"%>
b) <%@ page import="java.util.*"%>
Is there any performance issue using importing package with .*

Answer 1

Ofcourse there will be a performance issue. In the
second case (<%@ page import="java.util.*"%>
) , you are loading all the classes in java.util
package into your JSP, where as in the first case you
are getting only HashMap. So the second option will
affect the performance. Always import only the
required classes.
rgdsThen you have no idea how import works. The only difference at all would come at compile time. After the page is compiled, there would be no performance issue whatsoever.
The main reason for doing one or the other way (same for any Java class) is clarity for those reading the code. Meaning if you use the full import, when they see "HashMap" in the code, they can look at the import statements and be sure that it's in java.util package. But generally, most people are going to be familiar with the classes in the common packages, like java.util. So I wouldn't generally list the specific classes if you are using more then one from the same package. There are other considerations where packages have classes of the same name (java.sql.Date & java.util.Date) but generally, I would always just put the full class name in the code.