I was so wrong.
Three things wrong. The first is pedantic: you need to import IOException. The second though is one of those "scream out loud at the universe* questions: why the heck are you calling print() instead of write()?
Finally, do you think maybe you might need to worry about buffering of System.out's stream?
print() won't flush to the console unless you pass '\n' and auto-flushing is on. It will flush its internal buffer, but that's okay! The default System.out uses a BufferedOutputStream anyway:
FileOutputStream fdOut = new FileOutputStream(FileDescriptor.out);
...
new PrintStream(new BufferedOutputStream(fdOut, 128), true)
Obvious, right? Don't you love java.io? :)
Yes, which is the _problem_, not the _solution_.
To clarify: the problem isn't that the code makes too many syscalls.
public static void main(String[] args) throws IOException {
byte[] buffer = new byte[1 << 12];
for (;;) {
int nRead = System.in.read(buffer);
if (nRead == -1) return;
System.out.write(buffer, 0, nRead);
}
}
Try doing this:
dd if=/dev/random of=test_file bs=4000 count=100
java YourClass < test_file > test_output
diff test_file test_output> you need to import IOException
try {
...
} catch(Exception ex){ ... }
Edit: Or if you want to be just as pedantic, and not write an obnoxious catch-all
try {
...
} catch (java.io.IOException ex) { ... }As to why you'd want to use a catch, I think it's kind of sloppy to let the user see an uncaught exception. You might as well just do
public static void main(String args[]){
try {
...
} catch (Exception e) {
System.out.println("This is horrible software, and you shouldn't use it.");
}
}
This is bad code as he said.
You're conflating two things. I could just as easily have caught Throwable or Exception and not needed the import. The question is: what would you actually put in the handler that would be so much better? The actually provided sample code is much worse, as it prints to System.out instead of System.err, and it doesn't report an error to the parent process, so you muddy up the output (imagine if the file you were copying actually ended in "This is horrible software, and you shouldn't use it.", how would you even know) and there is not a terribly easy way to detect an error happened.
> This is bad code as he said.
It's not bad code to declare a static exception as escaping your method, particularly if you don't have any logic for handling it. It's bad code to have an exception handler that doesn't.
There are some, but they aren't the ones people usually think of when they say, "I'd always use X instead of Java".
So, for example, if you are in Python3, sys.in and sys.out are by default in text mode, which is not going to end well for anyone.
It's a trivial test, so I'll give you trivial input and not have you worry about "what if someone gives me random bytes".
The test isn't to demonstrate you know off the top of your head how to deal with an edge case. But if it were and I were allowed to pick my language, I'd pick bash and just write
catThe only edge case is knowing you need to flush the output, which is relevant whether you send ASCII text or not. The other edge cases around ASCII are just whether you use the correct API's or not.