When included import java.util.* then why include import java.util.Gregori

Question

Hi,
In my program I hava inported the java package like
import java.util.*;
import java.sql.*;
import java.text.*;
then for using some classes like Gregorial calender,Date etc,I have to again import
import java.util.Date;
import java.sql.PreparedStatement;
import java.util.GregorianCalendar;
As far as I know if I have import the above like
import java.util.*; then it means I can use any classes in java.util ,but if I am not importing
import java.util.GregorianCalendar;
import java.util.Date;
my program is giving error.Can somebody tell me,where my concept is wrong.
Thanks

Answer 1

import java.sql.*;
import java.util.*;
//import java.util.Date;  // <-- needed to avoid "the type Date is ambiguous"
public class PackageEg {
    public static void main(String[] args) {
        Date test = new Date();
}This code gives an error when I compile it, but if I include the
java.util.Date import it is good. The reason is that there are two
possible Date classes - one in java.util and one in java.sql. The
compiler cannot figure out which one I mean.
If I include a specific class like java.util.Date, then this one will be used
in preference to any .* imports. (These are called "imports on demand")
This explains why you need java.util.Date, but the other two are a
mystery. As far as I know PreparedStatement and GregorianCalander
are unique names within the packages you mention. Could you post
some code that will not compile unless the specific import statements
are there?