Arrays.sort... why sorting all arrays in class?

[innspiron]

Hi,

part of the code:
. . .
public static Integer arrayA [][];
public static Integer arrayB [][];
. . .
arrayA = .... //some values
. . .
arrayB = arrayA;

Arrays.sort(arrayB, new MatrixRowComparator());
. . .


The problem and question is why it sorts and arrayB and even arrayA? I call the method for srting only with arrayB.

Thanks

[Fubarable]

The answer: Arrays are objects and array variables are reference variables. So that means that this line here:

arrayB = arrayA;

indicates that the arrayB variable should now refer to the same object that is referred to by the arrayA variable. So any changes to this single object that is referenced by the two variables will seem to be seen by the two variables.

[innspiron]

thank you Fubarable for the answer and for quick response.

how do make these arrays equal but keep synchronization away? do I have to use loops for every element in array or there is another way? because arrayA is very long and using loops would take too much computation.

[Fubarable]

The only solution that I know of is to have the array variables refer to two completely different array objects. Perhaps you want to use System.arraycopy(...) here.

[innspiron]

done. thanks a lot. i love this forum. the response is awesome.

[Fubarable]

You're quite welcome!

[gcalvin]

thank you Fubarable for the answer and for quick response.

how do make these arrays equal but keep synchronization away? do I have to use loops for every element in array or there is another way? because arrayA is very long and using loops would take too much computation.

Note that System.arraycopy() likely uses exactly as much computation as doing it with your own loops, but it does have the advantage of being simpler. In other words, it probably doesn't make your program run any faster, but it does make it easier to understand, and that's reason enough for using it.

-Gary-