From type systems theory point of view, a class is an extensible module that can be used as a variable.

As mentioned in another reply, Java did not invent this, it was building upon Smalltalk and SELF, with a little bit of Objective-C on the side, and C++ like syntax.

Try to create a single function in Smalltalk, or SELF.

http://stephane.ducasse.free.fr/FreeBooks.html

https://www.strongtalk.org/

https://selflanguage.org/

It is also no accident that when Java came into the scene, some big Smalltalk names like IBM, one day of the other easily migrated their Smalltalk tooling into Java, and to this day Eclipse still has the same object browser as any Smalltalk environment.

Smalltalk,

https://www.researchgate.net/figure/The-Smalltalk-browser-sh...

Which you will find a certain similarity including with NeXTSTEP navigation tools, and eventually OS X Finder,

The code browser in Eclipse

https://i.sstatic.net/4OFEM.png

By the way, in OOP languages like Python, even functions are objects,

    Python 3.14.0 (tags/v3.14.0:ebf955d, Oct  7 2025, 10:15:03) [MSC v.1944 64 bit (AMD64)] on win32
    Type "help", "copyright", "credits" or "license" for more information.
    >>> def sum(x, y): return x + y
    ...
    >>> sum
    <function sum at 0x0000017A9778D4E0>
    >>> dir(sum)
    ['__annotate__', '__annotations__', '__builtins__', '__call__', '__class__', '__closure__', '__code__', '__defaults__', '__delattr__', '__dict__', '__dir__', '__doc__', '__eq__', '__format__', '__ge__', '__get__', '__getattribute__', '__getstate__', '__globals__', '__gt__', '__hash__', '__init__', '__init_subclass__', '__kwdefaults__', '__le__', '__lt__', '__module__', '__name__', '__ne__', '__new__', '__qualname__', '__reduce__', '__reduce_ex__', '__repr__', '__setattr__', '__sizeof__', '__str__', '__subclasshook__', '__type_params__']
    >>> type(sum)
    <class 'function'>
    >>> sum.__name__
    'sum'
    >>> sum.__class__
    <class 'function'>