simple concatination routine for a field

[law]

Hi all, I'm attempting to do this simple concatination routine in the iReport that results in errors on build. In "Variable Experssion" I have this: 

$V{likesStr}+=$F{likes}+","

Basically, I want to build a coma separated string of field $F{likes}, then later create an array out of it. I tried criating an array on the fly, directly, but couldn't get it populated correctly, the array was retaining only the very last value out of a set of values. I'm hoping to get my array out of the string I'm attaempting to build. 

The compiler error is: '(java.lang.String) variable_likesStr.getValue()', is a bad expression as the left hand side of an assignment operator

Any deailed suggestions will be much appreciated.

 

 

[law]

Here is what I discovered works for concatenating a field to a string:

 

$V{my_var_str}+$F{my_field}+','

 

Strange syntax, but does work.

 

 

[law]

Syntax for splitting the string into a String array:

 

$V{my_var_str}.split(",")