Difference in primitive data between Java and c++?

[hopesfall]

I've programmed in Java before and now that I'm learning C++ I'm curious as to how C++ treats primitive data differently than java. What are some ways C++ handles primitive data differently than Java that I should look out for?

[Athar]

It's not so much primitive data types that are handled differently, but rather non-primitive types.
However, you should be aware that the size of primitive data types depends on the platform in C++.

[Cubbi]

I don't know how Java initializes primitive data types, but here's a quick summary on how C++ does it:

static and thread-local storage duration: all primitive data types are zero-initialized unless specified otherwise, that is,

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#include <iostream> double f1; double f2 = 3.14; int main() { cout << f1 << '\n' << f2 << '\n'; }

0 3.14

automatic and dynamic storage duration: primitive data types are non-initialized if no initializer is used, and are zero-initialized if an empty initializer is used:

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#include <iostream> #include <memory> int main() { std::unique_ptr<double> pf1(new double); std::unique_ptr<double> pf2(new double()); double f1; double f2 = double(); std::cout << f1 << '\n' << f2 << '\n'; std::cout << *pf1 << '\n' << *pf2 << '\n'; }

garbage 0 garbage 0

And yes, unlike Java, the sizes of the primitive data types in C++ change platform to platform and compiler to compiler.

[LB]

Cubbi, in the first example, f1 doesn't print 0 for me, it prints some random number :\

[Cubbi]

@L B Talk about standards-defying compilers. That rule has been there since C++98 (just checked)