Using wildcards in import statement

Question

I typically use wildcards in my import statements. For example:
import javax.swing.*;
Are there any advantages, though, in specifying exactly which classes I am importing?
For example,
import javax.swing.JPanel;
import javax.swing.JLabel;
import javax.swing.JEditorPane;
import java.swing.JProgressBar;
// etc.
Specigically, is the resulting class file any smaller if I specify exactly which classes to use and does the Java runtime engine load faster if I specify exactly which classes I use in the import statemetents?
Thanks,

Answer 1

Import has precisely zero runtime impact. I believe it is used to help locate the specified class at runtime. Take the following 2 simple source files:
import java.util.Vector;
//import java.util.*;
public class VectorTest
     public static void main( String[] args )
          Vector v = new Vector();
          v.add("Item 1");
          v.add("Item 2");
          System.out.println( v.get(1) );
public class Vector
     public boolean add(Object o)
          return true;
     public Object get(int index)
          return "doh!";
}1) Run the code as is and "Item 2" is displayed
2) Recompile the code using the generic import and "doh!" is displayed.
The point is that by fully qualifying the import statement you are sure you are executing the correct class and not just some class that happens to be lying around somewhere in your classpath.