It can extend exactly one class and implement exactly one interface.

It can extend exactly one class and can implement multiple interfaces.

It can extend exactly one class or implement exactly one interface.

It can implement multiple interfaces regardless of whether it also extends a class.

It must be marked final.

It can be marked abstract.

It can be marked public.

It can be marked static.

You must have a reference to an instance of the enclosing class in order to instantiate it.

It does not have access to nonstatic members of the enclosing class.

It's variables and methods must be static.

It must extend the enclosing class.

Runnable r = new Runnable() { };

Runnable r = new Runnable(public void run() { });

Runnable r = new Runnable { public void run(){}};

System.out.println(new Runnable() {public void run() { }});