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From: Thomas Richter <thor@math.tu-berlin.de>
Newsgroups: comp.lang.java.programmer
Subject: Re: Java vs C++
Date: Sun, 06 Feb 2011 16:45:05 +0100
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Joshua Cranmer wrote:
> On 02/05/2011 11:13 PM, Lawrence D'Oliveiro wrote:
>> They are different things in Java as well.
> 
> The hell they aren't. In Java, there is only one instance of 
> LinkedList::add(T object). In C++, there are as many instances of 
> std::list<T>::front as times you use it.

I would say that's an implementation detail. A compiler/optimizer could 
check how many different implementations are needed and could merge 
those that are identical.

Besides that, where you use an object in java, one would use a pointer 
or a reference in C++, and hence the code would be identical, allowing a 
good compiler to merge the implementations. C++ and java are quite 
different in their tradition how to use types, or what types are. Java 
has two sorts of types: First class citizens like int or double that are 
copied, and second class citizens like classes that are referenced. C++ 
doesn't have that, objects are objects and ints and classes are handled 
alike.

> Try, for example, implementing both List<String> and List<Character> in 
> the same class. Java will tell you that you cannot do it. C++, on the 
> other hand, wouldn't bat an eye.

True.

>> The only time they become the
>> same thing is in “erasures” and “raw types”, which are backward-
>> compatibility mechanisms introduced to avoid breaking existing code that
>> doesn’t know about generics.
> 
> I think Java would likely have gone with much the same syntax even if 
> generics had been introduced in the beginning.

That's really a speculation. One could also speculate that if java would 
have used or required generics from the beginning, they would be closer 
to C++ templates and would not use type erasure; instead, they would be 
parametrized classes as they are in C++. It's really speculation.

Greetings,

	Thomas