Possible Loss of Precision - not caused by type conversion - Java

Thomas wrote:
> Hope I will not get banned for too many posts
> The code below does not want to compile. I get ""Possible Loss of Precision"
> in the lines:

> long last = 0L;
> long j;
> long i =2;
....
> 'j=last;'
>
> 'sito[j]=i;'

Maybe because
> Arrays must be indexed by int values; short, byte, or char values may also be used as index values because they are subjected to unary numeric promotion (§) and become int values. An attempt to access an array component with a long index value results in a compile-time error.
<http://java.sun.com/docs/books/jls/third_edition/html/arrays.html#10.4>

> 'increase(i,last);'
The value of i will not change from this call - you knew that, yes?

> private final static void increase(long x, long last){
> while(sito[last++]!=(long)0);
> x =(long)sito[last];
> }

The value of x from the assignment is thrown away.

--
Lew

U¿ytkownik "Lew" <lew@lewscanon.nospam> napisa³ w wiadomo¶ci
news:c7ednV5XKYs-LxLbnZ2dnUVZ_smonZ2d@comcast.com...
> Thomas wrote:
> > Hope I will not get banned for too many posts
> > The code below does not want to compile. I get ""Possible Loss of
Precision"
> > in the lines:
>
> > long last = 0L;
> > long j;
> > long i =2;
> ...
> > 'j=last;'
> >
> > 'sito[j]=i;'
>
> Maybe because
> > Arrays must be indexed by int values; short, byte, or char values may
also be used as index values because they are subjected to unary numeric
promotion (§) and become int values. An attempt to access an array component
with a long index value results in a compile-time error.
> <http://java.sun.com/docs/books/jls/third_edition/html/arrays.html#10.4>
>
> > 'increase(i,last);'
> The value of i will not change from this call - you knew that, yes?
>
> > private final static void increase(long x, long last){
> > while(sito[last++]!=(long)0);
> > x =(long)sito[last];
> > }
>
> The value of x from the assignment is thrown away.
>
> --
> Lew

The value of i will not change from this call - you knew that, yes?

Well I know, but I forgot .
Now after changing from long to int it works. Java sux if it doesn't allow
on more flexibilty. THX

Thomas wrote:
> Hope I will not get banned for too many posts
> The code below does not want to compile. I get ""Possible Loss of Precision"
> in the lines:
> 'j=last;'
....

I don't understand that particular error, and Eclipse did not report it.
j and last are both of type long, so the assignment should be valid.

There is an error on each attempt to use a long as an array index. That
is due to the unfortunate decision to limit Java arrays by using int for
array size and index.

Patricia

"Lew" <lew@lewscanon.nospam> napisa� w wiadomo�ci
>> Maybe because
>>> Arrays must be indexed by int values; short, byte, or char values may also be used as index values because they are subjected to unary numeric promotion (�) and become int values. An attempt to access an array component with a long index value results in a compile-time error.
>> <http://java.sun.com/docs/books/jls/third_edition/html/arrays.html#10.4>

Thomas wrote:
> Now after changing from long to int it works. Java sux if it doesn't allow
> on more flexibilty. THX

If you have an array of long with 2 billion entries it will occupy over 16GB
of heap - the issue of your index will be moot.

Since arrays are limited to (Integer.MAX_VALUE + 1) entries, using a long
index risks an out-of-bounds problem, hence the restriction to int indexes.
You used a long, which in conversion to int risks losing precision, and this
is the error you got. In today's world an array with more entries than that
is not manageable anyway.

You can always downcast the long index to int for use in the indexing expression.

I do not begin to guess how you can characterize this as an issue of
"flexibility".

--
Lew

On Jul 7, 9:44 pm, Lew <l...@lewscanon.nospam> wrote:
> "Lew" <l...@lewscanon.nospam> napisa? w wiadomo?ci
> I do not begin to guess how you can characterize this as an issue of
> "flexibility".

I agree. Plus no one 'forces' anyone to use arrays. You can always use
'Arraylist' if you want _flexibility_.

getsanjay.sharma wrote:
> On Jul 7, 9:44 pm, Lew <l...@lewscanon.nospam> wrote:
>> "Lew" <l...@lewscanon.nospam> napisa? w wiadomo?ci
>> I do not begin to guess how you can characterize this as an issue of
>> "flexibility".
>
> I agree. Plus no one 'forces' anyone to use arrays. You can always use
> 'Arraylist' if you want _flexibility_.

Although it lacks the particular feature the OP wanted, the ability to index
outside the int range.

--
Lew

On Jul 7, 10:55 pm, Lew <l...@lewscanon.nospam> wrote:
> Although it lacks the particular feature the OP wanted, the ability to index
> outside the int range.

I know it sounds expensive memory wise but OP can always use the Hash
Map and with the autoboxing capability, he can index outside the int
range.

On Jul 7, 12:44 pm, Lew <l...@lewscanon.nospam> wrote:
> If you have an array of long with 2 billion entries it will occupy over 16GB
> of heap - the issue of your index will be moot.

Yeah, since 640K really ought to be enough for anybody, even far into
the future ...

Lew wrote:
> "Lew" <lew@lewscanon.nospam> napisa� w wiadomo�ci
>>> Maybe because
>>>> Arrays must be indexed by int values; short, byte, or char values
>>>> may also be used as index values because they are subjected to unary
>>>> numeric promotion (�) and become int values. An attempt to access an
>>>> array component with a long index value results in a compile-time
>>>> error.
>>> <http://java.sun.com/docs/books/jls/third_edition/html/arrays.html#10.4>
>
> Thomas wrote:
>> Now after changing from long to int it works. Java sux if it doesn't
>> allow
>> on more flexibilty. THX
>
> If you have an array of long with 2 billion entries it will occupy over
> 16GB of heap - the issue of your index will be moot.

Not if you have a 64 bit JVM and a server with a large memory.

Patricia