[kragen]

Java was derived from C++, Smalltalk, and arguably Cedar, and one of its biggest differences from C++ and Smalltalk is that in Java things like integers, characters, and booleans aren't objects, as they are in C++ and Smalltalk. (Cedar didn't have objects.)

[bluGill]

Right. Everything a user can do is object, but there are a few non-object built ins. (they are not objects in C++ either, but C++ doesn't make everything you write be an object)

[kragen]

In C++ integers and characters are objects. See https://en.cppreference.com/w/cpp/language/objects.html, for example, which explicitly mentions "unsigned char objects", "a bit-field object", "objects of type char", etc.

[dpark]

I feel this is a case of using the same word to mean something different. C++ “object” here seems to mean something more akin to “can be allocated and stuffed into an array” than a Smalltalk-type object.

i.e. C++ primitive types are defined to be objects but do not fit into a traditional object-oriented definition of “object”.

[kragen]

Yes, many people believe that C++ isn't really "object-oriented", including famously Alan Kay, the inventor of the term. Nevertheless, that is the definition of "object" in C++, and Java is based on C++, Smalltalk, and Cedar, and makes an "object"/"primitive" distinction that C++, Smalltalk, and Cedar do not, so "Java [did something] by deciding everything must be an object" is exactly backwards.

[bluGill]

I'm not sure who invented "object oriented", but objects were invented by Simula in 1967 (or before, but first released then?) and that is where C++ takes the term from. Smalltalk-80 did some interesting things on top of objects that allow for object oriented programming.

In any case, Alan Kay is constantly clear that object oriented programming is about messages, which you can do in C++ in a number of ways. (I'm not sure exactly what Alan Kay means here, but it appears to exclude function calls, but would allow QT signal/slots)

[kragen]

The specific thing you can do in Smalltalk (or Ruby, Python, Objective-C, Erights E, or JS) that you can't do in C++ (even Qt C++, and not Simula either) is define a proxy class you can call arbitrary methods on, so that it can, for example, forward the method call to another object across the network, or deserialize an object stored on disk, or simply log all the methods called on a given object.

This is because, conceptually, the object has total freedom to handle the message it was sent however it sees fit. Even if it's never heard of the method name before.

[gpderetta]

C++ standard gets the definition of object from the C standard, i.e. a bunch of memory with a type.

Nothing to do with the objects of OOP.

[dpark]

To be clear, I’m not trying to pick at whether or not C++ is “really object oriented”.

What I’m saying is that the discrepancy between primitives in C++ and Java is entirely one of definition. Java didn’t actually change this. Java just admitted that “objects” that don’t behave like objects aren’t.

[kragen]

On the contrary, Java objects are very different from C++ objects, precisely because they lack a lot of the "primitive-like" features of C++ objects such as copying, embedding as fields, and embedding in arrays. (I'm tempted to mention operator overloading, but that's just syntactic sugar.)

[bluGill]

Just like Java, you cannot inherit from integers or characters. Depending on what you want to do with them that might or might not matter.

[kragen]

That's true, and in Smalltalk it's not true. In Cedar there is no inheritance. At any rate it's not a case of Java making more things objects than its forebears.

[lmm]

> At any rate it's not a case of Java making more things objects than its forebears.

There are other cases though. E.g. in C++ you could always have function pointers which were not objects and functions which were not methods. In Java you had to use instances of anonymous classes in place of function pointers, and all of your functions had to be (possibly static) methods.

[kragen]

Function pointers in C++ are "objects", and the difference between static methods and C-style functions which are not methods seems purely syntactic to me, or at best a question of namespacing. Regardless, static methods are not objects either in Java or in C++, so that is also not a case of something being an "object" in Java and not in C++.