[rules-users] problem with drools

[Sandhya Sree]

hi,
im new to drools..im trying to create a project as follows. i have a class
called Monitor  which monitors a folder and creates two lists called
fileOld( which is the list of filenames in that folder at time t1)  and
fileNew(which is the list of filenames in that folder at time t2). i have
another class called FileData which contains two members fileOld and
fileNew (list of strings) with getters,setters and constructor. fileOld and
fileNew from Monitor Class are passed to FileData class.

now i have to compare these two lists in a rule file and if they are not
equal i have to print the lists of files added/ deleted. how to do this in
drools.

here is my rule file:

rule "files are equal"

    when
        FileData(fileOld == fileNew)

    then
       System.out.println("files are equal");


end

rule "files not equal"

  when
        not FileData(fileOld == fileNew)
    then
       System.out.println("files are not equal");
       difference(FileData.getFileOld(),FileData.getFileNew());

end


function void difference(List fileOld, List fileNew)
{


   ArrayList<String> add = new ArrayList<String>(fileNew);
   add.removeAll(fileOld);
   System.out.println("files Added: " + add);

   ArrayList<String> remove = new ArrayList<String>(fileOld);
   remove.removeAll(fileNew);
   System.out.println("files Removed: " + remove);
}


but this displays the following error...

Rule Compilation error : [Rule name='files not equal']
Cannot make a static reference to the non-static method getFileOld() from
the type FileData
Cannot make a static reference to the non-static method getFileNew() from
the type FileData



what can be done??
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