bit shift question.

[Robin John]

Am I doing this correct ?

    
byte[] buffer = new byte[16 << 16];
int bytesRead = 0;
while((bytesRead = inputFileStream.read(buffer)) != -1) {
//writing ...
}
.
.
.
.
.
.
.
bos = new BufferedOutputStream(fos, 1024*2048);
while((bytesRead = fIn.read(buffer)) != -1) {
// writing...
}

I wanted to confirm if I am using the bit shift operators correctly.

1) In the first part, does it mean byte[] buffer = new byte[16 * 2 to the power 16] ? what is the memory size ?
2) In the second part what buffer size am I allocating ?

Am I at risk of running out of memory in any case if say I have 3 threads running each handling a 800 MB file ?

Thanks in advance.

[Tom Reilly]

Try looking at buffer.length to see if you did it right.

[Campbell Ritchie]

Yes, 16 << 16 is 16 * 1^16. But surely you would use hex and write 0x10?
Try this

System.out.printf("16 << 16 = %d = 0x%<x%n"16 << 16);
System.out.printf("1024 * 2048 = %d = 0x%<x%n", 1024 * 2048);

As for the bit about memory, that is hardly a "beginning" topic, so I shall move this thread.>

[Campbell Ritchie]

I earlier wrote: . . . I shall move this thread.

. . . and I presume you found the mistakes in my posting?

[Robin John]

yes got the mistakes, thanks for the reply : ) ,

now getting back to the memory issues ?

2) In the second part what buffer size am I allocating ?

Am I at risk of running out of memory in any case if say I have 3 threads running each handling a 800 MB file ?

Any help would be appreciated...

[Henry Wong]

Robin John wrote:

2) In the second part what buffer size am I allocating ?

Am I at risk of running out of memory in any case if say I have 3 threads running each handling a 800 MB file ?

Any help would be appreciated...

Why don't you tell us? .. in this topic, it was recommended that ... (1) you print out the buffer length, (2) you print out the value calculated from the expression, or (3) you work out the math on paper. Each of these options are easy and can be done in a few minutes.

As for running out of memory, we don't know the amount of memory of your machine, nor how much heap you have configured for your JVM.

Henry

[Robin John]

32-bit system

VM arguments - min heap 1024 and max 1600

2GB RAM

please let me know if you need more info ?

and I meant to quote only the memory part... before I could edit it.. you have replied : )

Thanks.

[Henry Wong]

Robin John wrote:
and I meant to quote only the memory part... before I could edit it.. you have replied : )

Well, what was the result? The number of elements in the byte array should tell you closely, the memory that your application needs (just for the array).

Henry

[David Newton]

Why are you bothering using a shift, anyway?

[Robin John]

: ) hey David,

I dont know.. what legacy application I'm maintaining.. they want everything to be consistent : D through out the code...

I think its cool : )


Regards.

[David Newton]

In this case, it's only cool if it actually accomplishes something useful, which it doesn't: back before optimizing compilers, when we were writing in assembly, etc. a shift made sense. That hasn't been the case for quite some time now.

[Robin John]

O ya.. I'll keep that in mind... use integers instead ! : ) thanks