Re: On Java and C++

In comp.lang.java.advocacy, Mishagam
<noemail@provider.com>
 wrote
on Fri, 28 Apr 2006 15:59:33 GMT
<FZq4g.21858$Sa1.9467@tornado.southeast.rr.com>:


I think he's serious, but then RAII may or may not be a big issue. I
for one can't tell at this point.

The typical usage paradigm is opening a file:

[a] normal case.

File f = ...; // optional
FileInputStream fs = new FileInputStream(f);

....

fs.close();

[b] with exception handling.

File f = null;
FileInputStream fs = null;

try
{
    f = ...;
    fs = new FileInputStream(f);
    doSomething(fs);
}
catch(Exception ex)
{
    log.error("Oops", ex);
}
finally
{
    if(fs != null) try { fs.close(); } catch(Exception ex2) {}
}

I've seen prettier but the general idea is clear enough.

In C++:

{
    std::ifstream ifs("pathname");
    doSomething(ifs);
}

is far simpler; if an exception is thrown std::ifstream::~ifstream
is also guaranteed to be called. However, I have no idea what

{

    std::ifstream ifs1("pathname");
    std::ifstream ifs2(ifs1);
    doSomething(ifs1);
    doSomething(ifs2);
}

or

{

    std::ifstream ifs1("pathname");
    std::ifstream ifs2("path2");

    ifs1 = ifs2;

    doSomething(ifs1);
    doSomething(ifs2);
}

are intended to do; the most logical would be the C++ equivalent
of dup2(). In Java, one runs into object aliasing issues:

FileInputStream fs1 = ...;
FileInputStream fs2 = fs1;

in the foregoing fs1 and fs2 refer to *the same object*. This is either
a bug or a feature.

--
#191, ewill3@earthlink.net
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