On: Complaints I'm Seeing About Java

[mynameishere]

One complaint I've always had that no one else seems to bring up: I can't take a flat array of bytes and map a struct over it. You have to fake that out in the most lamentable way...

I guess most people don't need to do that anymore.

[tlrobinson → mynameishere]

It's also annoying that there aren't any unsigned (primitive) data types in Java. You end up doing weird bitwise operations to get the correct results.

for example, to convert an unsigned byte to an integer:

    byte a = (some unsigned byte data);
    int b = 0xff & a;

[Tichy → mynameishere]

I guess you are right, because I don't even understand what you mean?

[Goladus → Tichy]

He wants fine control over memory allocation.

Most people who want that much control use C or C++.

[mynameishere → Tichy]

struct MyStruct { int a; } ;

char bytes[]={0,1,0,0};

MyStruct *myStruct=((MyStruct [asterisk] )bytes);

...myStruct->a is now 256.

How do you format code here?

[Tichy → mynameishere]

I see - I am glad that Java does not support that ;-)

Presumably what you want can be achieved with ByteArrayInputStream and DataInputStream.

    byte[] bytes = {0,1,0,0};
    DataInputStream in = new DataInputStream(new ByteArrayInputStream(bytes));
    int a = in.readInt();
    in.close();

untested, but something like that... There is also object serialization. I never had a use case for what you describe.

(format code with 4 leading spaces)

[boucher → Tichy]

object serialization is horribly inefficient in java.

[mynameishere → Tichy]

Guess how many CPU cycles my C code requires.

[Tichy → mynameishere]

What time sensitive operation requires you to transform byte arrays into objects? I assumed something like reading from disk or network, and then CPU cycles are usually not the bottleneck.

Anyway, no doubt that you can write faster code in C, but I am glad that I did not have to look at pointer arithmetic for the last 8 years. Using your array->struct technique would be a major headache if the struct get's more complex.

[boucher → Tichy]

There are plenty of other practical use cases for this kind of control. For example, casting an array of byte[]s to an array of int[]s. It's not hard to convert using a ByteBuffer, but its still annoying. You and up duplicating a ton of memory for no good reason.

[brlewis → mynameishere]

You're assuming a 32-bit little-endian system.

Indent at least two spaces for code.