Why would anyone do that :/
I don't know
A new class creates more overhead than a new instance of an existing class. The new class, even if it is an anonymous one, has to be loaded, linked, and initialized: JLS 12.3 - 12.4 Linking and Initialization of Classes and Interfaces
This adds memory and processing overhead for a savings of 2 or 3 keystrokes.
Plus, when the code runs multiple times, each execution creates not one object, but 2 adding a non trivial amount of overhead if the code is in a method that runs frequently.