importing classes using wildcards

Question

If I say:

import java.awt.event.ActionListener;

I get the ActionListener Class. If I say:

import java.awt.event.*;
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Answer 1

Remember that the import statement is just for convenience. It is there to make it possible for you to use the short name of a class rather than the fully qualified name.

The package name structure in Java corresponds to a directory structure. So you can think of it as a directory named java and in that directory there are several other directories such as awt and io etc.

When you say

import java.awt.*;

you are basically saying that you want to use the short name for all the classes in the directory named awt inside the directory named java. So if you use a class name in your code like this:

   List mylist;

Then the compiler will attempt to find either a class named List in the current package or a class named java.awt.List.

So if you have a directory inside the awt directory called event and you have a class named ActionEvent in that directory, the fully qualified name is:

  java.awt.event.ActionEvent

and the import statement above does not help. Hence the reason for needing another import statement

  import java.awt.event.*;

Now, if you use the class ActionEvent the compiler looks for a class named ActionEvent in the current directory, or java.awt.ActionEvent or java.awt.event.ActionEvent until it finds one.