Cannot convert double to long..

[Ann Ron]

Hi,
I am writing a code :
double repid;
double repstr;
repid = Math.random( );
repstr = (long) ( repid * 10000000000000 );
I get this error : Integer Literal Out of Range,Decimal int literals must be in a certain range...
I tried to make my repstr type "long" in order to accomodate the multiplication I do, but it still gives me the same error.
error: Integer Literal Out of Range
Any clue how to solve this.I know Java needs explicit casting also but I dont know what to do.
Any help will be appreciated,Thanks in adavnce.
Ann

[Ernest Friedman-Hill]

Hi Ann,
Welcome to JavaRanch!
It's not complaining about the type of the variable, but the type of the "literal" -- i.e., the hard-coded value. The number you're writing is too large to represent as a 32-bit int, hence the error. You can write a long literal by putting an "L" after it, like 1000000000000L. But since you're assigning to a double, why not make it a double literal by putting a decimal point or a letter "D" at the end: "100000000000000." or "100000000000D" .

[Ann Ron]

Thanks a lot,It worked.I feel so silly asking such a basic question but I am new to Java is my only cop-out.
Thanks
Ann

[Ann Ron]

Hi Ernest,

[Ann Ron]

Hi Ernest,
The code compiles fine but it doesn't do what it is supposed to be doing.I need a 13 digit long number from repstr which is why i multiply it with 10000000000000.When I do like you suggested it still gives me only 7 digit long value.So I thought I would make repstr long and then do as follows :
double repid;
long repstr;
repid = Math.random( );
repstr = repid * 10000000000000D ;
But this gives me another error : Incompatible type for =. Explicit cast needed to convert double to long.How can I have the repstr to be 13 digits long and do this.PLease help.
Thanks in advance.
Ann

[Ernest Friedman-Hill]

Can you show me what you're doing with repstr that's leading to the 7 vs. 13-digit number? I'm not quite sure what you're saying.
[ October 21, 2003: Message edited by: Ernest Friedman-Hill ]

[Lisa D'Aniello]

Hi Ann,
I'm not sure what your solution is for getting your 13 digit long, but in your code below you're doing the following:
long = double * double (this is a no no)
That should be the source of your current error.
Hope this helps at least a little bit,
Lisa M.

double repid;
long repstr;
repid = Math.random( );
repstr = repid * 10000000000000D ;
But this gives me another error : Incompatible type for =. Explicit cast needed to convert double to long.How can I have the repstr to be 13 digits long and do this.PLease help.
Thanks in advance.
Ann

[Ann Ron]

Hi,
This is what I do with repstr..
double repid;
long repstr;
repid = Math.random( );
repstr = (long) repid * 10000000000000L ;//This is different
repstr1 = String.valueOf( repstr ) ;
repstr2 = repstr1.substring(13);
doc.replaceItemValue("RepositoryID",repstr2 );
This repstr2 is actually giving me a 7 digit value instead of the 13 long.
When I do the above,cast the repstr as long then it compiles fine but when I run this code,it gives me an error StringIndex out of bounds exception.
I am trying all sorts of combinations of long and double and casting,nothin seems to be working..Any suggestions...?
Thanks,
Ann

[Ernest Friedman-Hill]

OK, let's see. Each code example you've shown me is a little different and thus has slightly different problems. In this one, you may be surprised to learn that the line

  repstr = (long) repid * 10000000000000L ;//This is different

computes 0! The cast applies to "repid" alone, which gives 0 (casting to integer type truncates towards 0). If you add some parentheses around the whole expression, like this:

  repstr = (long) (repid * 10000000000000L);

then repstr will be a number which most of the time has thirteen digits. Sometimes it will have fewer though (if repid is between 0 and 0.1).
OK, now, I can't even imagine what you're doing calling repstr1.substring(13). This function gives you the substring of a string starting with the character at the given index. For a 13-character string, this will be "", the empty string. For a shorter string, which this one will occasionally be, you'll get an index out of bounds problem.
So basically you just want a 13-digit random string, is that it -- i.e., a number between 10E12 and 10E13. The classic forumla for a random number between A and B looks like

  ((B - A + 1) * random()) + A

So your string would be

final long ten13 = 10000000000000L;
final long ten12 = 1000000000000L;
String key =
  String.valueOf((long) ((ten13 - ten12 + 1) * Math.random()) + ten12);

where I've added a few constants to make it easier to read.
[ October 22, 2003: Message edited by: Ernest Friedman-Hill ]

[Ann Ron]

That solved it.I now get a 13 digit long repstr.
Thanks a tonne,for all your help and patience.
Ann