Question

I’m new to Java. I tried to look up on this grammar but could not find it. Could you please point out what this is?

class actions{
   ...
   public ActionListener WHATISTHIS = new ActionListener () {
      public void actionPerformed (ActionEvent event) {
         String action = event.getActionCommand ();
         show_error ("Key unimplemented: " + action + ": "
                    + keys.valueOf (action).get_html ());
         refresh (action);
      }
   };
   ...

Is WHATISTHIS an object with type ActionListener? And the stuff {..} after new a junk of code for the object? I am confused. Normally I see something like:

[MODIFIER] [TYPE] obj = new [TYPE]();

But in the case above, it is:

[MODIFIER] [TYPE] obj = new [TYPE](){...};

Answer 1

This type of class is called anonymous class.

It declares and instantiates a class that implements ActionListener.