[rules-users] Multiple Object Referencing problem

[Fnu Mahalakshmi]

Hi,

I am trying out this example from the book :

public class Room {

    private String name

    // getter and setter methods here

}

public classs Sprinkler {

    private Room room;

    private boolean on;

    // getter and setter methods here

}

public class Fire {

    private Room room;

    // getter and setter methods here

}

I load 2 input files: 1. with data of fire and Room { f1, r1;f2, r2}
                           2. with data of sprinkler and Room { " ", r1; " " , r2}

I am writing rule " if fire exists in room start sprinkler" { so if f1 and r1 in this case: I should get s1, r1 }
when
    Fire($room : room)
    $sprinkler : Sprinkler( room == $room, modified == false )
Then
    $sprinkler.setmodified(true);
    modify( $sprinkler ) { setSprinkle( "s1" ) };
end

But this gives me error:
Exception in thread "main" java.lang.NullPointerException
      at java.io.Writer.write(Unknown Source)
      at com.org.RulesTest.main(RulesTest.java:58)

>From what I observed this rule is not getting fired at all.
I want this rule to be fired on the data in my second input file.
The rules for my first input file get executed properly.

Can any1 tell me where I am going wrong??
Is there any way in which we can use the modified data { after rules are fired on the first input data and it is  modified}to fire another set of rules on the same input depending on the next input file???

Thank you.

-M
</pre>

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