How to perform add,subtract on 'Double' Fields

[thelinuxmaniac]

Hi,

I have three Double fields as:

 

Code:

<field name="grandtotal" class="java.lang.Double"/>
<field name="amount_paid" class="java.lang.Double"/>
<field name="previous_due" class="java.lang.Double"/>

 

And I want to calculate Balance using the formula:

BALANCE_DUE = grandtotal+previous_due-amount_paid

 

When I define a variable to calculate BALANCE_DUE as shown below

Code:

[code] <variable name="BALANCE_DUE" class="java.lang.Double" resetType="Report" calculation="Nothing"> <variableExpression><![CDATA[sUM( $F{grandtotal} + $F{amount_paid})]]></variableExpression> </variable>

 

I get the following error message

Code:

[code] et.sf.jasperreports.engine.JRException: Errors were encountered when compiling report expressions class file: 1. The operator + is undefined for the argument type(s) java.lang.Double, java.lang.Double value = (java.lang.Double)(SUM( ((java.lang.Double)field_grandtotal.getValue()) + ((java.lang.Double)field_amount_paid.getValue()))); <------------------------------------------------------------------------------------------------> 2. The operator + is undefined for the argument type(s) java.lang.Double, java.lang.Double value = (java.lang.Double)(SUM( ((java.lang.Double)field_grandtotal.getOldValue()) + ((java.lang.Double)field_amount_paid.getOldValue()))); <------------------------------------------------------------------------------------------------------> 3. The operator + is undefined for the argument type(s) java.lang.Double, java.lang.Double value = (java.lang.Double)(SUM( ((java.lang.Double)field_grandtotal.getValue()) + ((java.lang.Double)field_amount_paid.getValue()))); <------------------------------------------------------------------------------------------------> 3 errors

Why cannot + and - operators be applied to Double value (and only applied to strings) ? Please suggest any other possible method to calculate the BALANCE_DUE.

[rsilverns.sympatico.ca]

It is related to the underlying functionality of the '+' operator in java. Strings are able to be appended using the '+' even though they are objects, its an exception to the rule.

 

To add the Double objects you have to treat each field as an object and use dot-notation in your expression fro the BALANCE_DUE field.

 

new Double($F{grandtotal}.doubleValue() + $F{previous_due}.doubleValue() - $F{amount_paid}.doubleValue())

 

Notice that there is no ";" at the end of the expression. Now if one of the above objects is null, a null ptr expression would occur. To avoid this you have to modify the expression as follows...

 

 

new Double(

$F{grandtotal}==null?0.0:$F{grandtotal}.doubleValue() +

$F{previous_due}==null?0.0:$F{previous_due}.doubleValue()

-

$F{amount_paid}==null?0.0:$F{amount_paid}.doubleValue())

 

Now there is a check to use 0.0 if the object is null. This depends on your data source etc. of course, if the object could be null.

 

hth,

 

Robin

[rcracel]

Or you can make sure your compiler is compatible with java5 and it should handle the boxing/unboxing for you.

 

Hope this helps,

RC

[thelinuxmaniac]

Thanx Robin for that quick reply.

[rsilverns.sympatico.ca]

Yw

Post edited by: rsilver@bfm.bm, at: 2006/10/11 19:39