formula expression double

[purnama]

how to use expression with double ?

i have expression in jasper 2.0.2 like this :

($F{paymen}!= new Double(0) ? $F{payStat}+":"+$F{paymen1}.intValue()+"\n" : "" )

but it didn't work ?

 

i need your help..

btw, sory if my english is bad

 

[slow]

use:

($F{paymen}!=null && $F{paymen}.doubleValue()!=0)?($F{payStat}+":"+$F{paymen1}.intValue()+"\n"):""

i suppose:
-paymen is a Double object... and
-payStat is a String and
-paymen1 is a Integer.

if paymen1 is a Double, then use,

($F{paymen}!=null && $F{paymen}.doubleValue()!=0)?($F{payStat}+":"+$F{paymen1}.doubleValue()+"\n"):""

 

_________________________________________

if it works... give me KARMA points please!    : ) 
_________________________________________

listening:   Nine Inch Nails - Complication

[purnama]

ok thank you Mr.slow and i will give you KARMA points.

but i have a question. why expression ->

1. $F{paymen}!= new Double(0) ?

or

2. $F{paymen}!= 0 ?

didn't work. can you explain to me

[slow]

the explanation will give me some extra karma points? :)

when you work with java objects the the "equal" or "==" concept must be relative to them (object)...

so, when you declare:

Double A = new Double(0);
Double B= new Double(0);

the expression

if (A==B) then System.out.println("OK :) ")
else System.out.println("NO  :( ")

will print NO :(

this happen because you try to compare the value of A and B that aren't 0, but some value on memory location that contains the 0 value... so A point to a location, B point to another location... and all two location contains the 0 value... but their real values (remember A and B is a memory location!) are different.

if you declare 

Double A = new Double(1);
Double B = A;

then

if (A==B) then System.out.println("OK :) ")
else System.out.println("NO  :( ")

will print OK :) only because A and B point to the same memory location... (remember that also in this case you are comparing memory location, not double values!)

SO... the best (and only) way to perform a comparison is to compare the VALUES of the two variables...

if (A.doubleValue()==B.doubleValue()) then System.out.println("OK :) ")
else System.out.println("NO  :( ")

will print OK

a.doubleValue() returns a basic double value, not an object... so its value can be used in algebra, comparison etc etc.

--------------------------------------------

in reference to your question:

$F{paymen}!= new Double(0) ?

it doesn't work because $F{paymen} is a Double object... and new Double(0) is another Double object pointing to different memory location
in this case use:

$F{paymen}.doubleValue()!= new Double(0) .doubleValue()
that is equal to:
$F{paymen}.doubleValue()!= 0

the second question:

$F{paymen}!= 0 ?
it doesn't work because you try to compare a Double object with an int/double basic  value... this mean that you try to compare a memory location value with the 0 value!
the correct form is:
$F{paymen}.doubleValue()!= 0

 

I hope what I wrote may make your ideas more clear.

 

_________________________________________

if it works... give me KARMA points please!    : ) 
_________________________________________

listening:  Nine Inch Nails - The Day The World Went Away

 

Post Edited by slow at 06/15/2010 07:35

[purnama]

ooo.. Now i understand.

thank you very much for your answer...

 

and i will give some extra karma points.. ha ha ha