Answer: No! Here is an example which does not work. However, it does work if the javax.swing.*; line is uncommented. The package code is here and is installed in subdirectory classes.
import classes.*;
//import javax.swing.*;
import java.awt.*;

class I extends JFrame {
   public I () { getContentPane().add(new JLabel("Class ImportTest")); }
}

public class ImportTest {
   public static void main (String arg[]) {
      I i = new I();
      Z z = new Z();
      i.setSize(200,100);
      z.setSize(100,200);
      i.setVisible(true);
      z.setVisible(true);
   }
}