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<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>Hi,<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>I am trying out this example from the book :<o:p></o:p></span></font></p>
<pre><font size=2 color=black face="Courier New"><span style='font-size:10.0pt'>public class Room {<o:p></o:p></span></font></pre><pre><font
size=2 color=black face="Courier New"><span style='font-size:10.0pt'> private String name<o:p></o:p></span></font></pre><pre><font
size=2 color=black face="Courier New"><span style='font-size:10.0pt'> // getter and setter methods here<o:p></o:p></span></font></pre><pre><font
size=2 color=black face="Courier New"><span style='font-size:10.0pt'>}<o:p></o:p></span></font></pre><pre><font
size=2 color=black face="Courier New"><span style='font-size:10.0pt'>public classs Sprinkler {<o:p></o:p></span></font></pre><pre><font
size=2 color=black face="Courier New"><span style='font-size:10.0pt'> private Room room;<o:p></o:p></span></font></pre><pre><font
size=2 color=black face="Courier New"><span style='font-size:10.0pt'> private boolean on;<o:p></o:p></span></font></pre><pre><font
size=2 color=black face="Courier New"><span style='font-size:10.0pt'> // getter and setter methods here<o:p></o:p></span></font></pre><pre><font
size=2 color=black face="Courier New"><span style='font-size:10.0pt'>}<o:p></o:p></span></font></pre><pre><font
size=2 color=black face="Courier New"><span style='font-size:10.0pt'>public class Fire {<o:p></o:p></span></font></pre><pre><font
size=2 color=black face="Courier New"><span style='font-size:10.0pt'> private Room room;<o:p></o:p></span></font></pre><pre><font
size=2 color=black face="Courier New"><span style='font-size:10.0pt'> // getter and setter methods here<o:p></o:p></span></font></pre><pre><font
size=2 color=black face="Courier New"><span style='font-size:10.0pt'>}<o:p></o:p></span></font></pre>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>I load 2 input files: 1. with data of fire and Room { f1,
r1;f2, r2}<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>
2. with data of sprinkler and Room { “ “, r1; “ “ , r2}<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>I am writing rule “ if fire exists in room start
sprinkler” { so if f1 and r1 in this case: I should get s1, r1 }<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=black face="Courier New"><span
style='font-size:10.0pt;font-family:"Courier New";color:black'>when<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=black face="Courier New"><span
style='font-size:10.0pt;font-family:"Courier New";color:black'>
Fire($room : room)<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=black face="Courier New"><span
style='font-size:10.0pt;font-family:"Courier New";color:black'>
$sprinkler : Sprinkler( room == $room, modified == false )<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=black face="Courier New"><span
style='font-size:10.0pt;font-family:"Courier New";color:black'>Then<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=black face="Courier New"><span
style='font-size:10.0pt;font-family:"Courier New";color:black'>
$sprinkler.setmodified(true); <o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=black face="Courier New"><span
style='font-size:10.0pt;font-family:"Courier New";color:black'>
modify( $sprinkler ) { setSprinkle( “s1” ) };<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=3 color=black face="Times New Roman"><span
style='font-size:12.0pt;color:black'>end<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=3 color=black face="Times New Roman"><span
style='font-size:12.0pt;color:black'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=3 color=black face="Times New Roman"><span
style='font-size:12.0pt;color:black'>But this gives me error:<o:p></o:p></span></font></p>
<p class=MsoNormal style='text-autospace:none'><font size=2 color=red
face="Courier New"><span style='font-size:10.0pt;font-family:"Courier New";
color:red'>Exception in thread "main" </span></font><u><font size=2
color=navy face="Courier New"><span style='font-size:10.0pt;font-family:"Courier New";
color:navy'>java.lang.NullPointerException</span></font></u><font size=2
face="Courier New"><span style='font-size:10.0pt;font-family:"Courier New"'><o:p></o:p></span></font></p>
<p class=MsoNormal style='text-autospace:none'><font size=2 color=red
face="Courier New"><span style='font-size:10.0pt;font-family:"Courier New";
color:red'> at java.io.Writer.write(Unknown
Source)</span></font><font size=2 face="Courier New"><span style='font-size:
10.0pt;font-family:"Courier New"'><o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=red face="Courier New"><span
style='font-size:10.0pt;font-family:"Courier New";color:red'> at
com.org.RulesTest.main(</span></font><u><font size=2 color=navy
face="Courier New"><span style='font-size:10.0pt;font-family:"Courier New";
color:navy'>RulesTest.java:58</span></font></u><font size=2 color=red
face="Courier New"><span style='font-size:10.0pt;font-family:"Courier New";
color:red'>)<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=red face="Courier New"><span
style='font-size:10.0pt;font-family:"Courier New";color:red'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 color=red face="Courier New"><span
style='font-size:10.0pt;font-family:"Courier New";color:red'>From what I
observed this rule is not getting fired at all.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=red face="Courier New"><span
style='font-size:10.0pt;font-family:"Courier New";color:red'>I want this rule
to be fired on the data in my second input file.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=red face="Courier New"><span
style='font-size:10.0pt;font-family:"Courier New";color:red'>The rules for my
first input file get executed properly.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=red face="Courier New"><span
style='font-size:10.0pt;font-family:"Courier New";color:red'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 color=red face="Courier New"><span
style='font-size:10.0pt;font-family:"Courier New";color:red'>Can any1 tell me
where I am going wrong??<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=red face="Courier New"><span
style='font-size:10.0pt;font-family:"Courier New";color:red'>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???<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=red face="Courier New"><span
style='font-size:10.0pt;font-family:"Courier New";color:red'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 color=red face="Courier New"><span
style='font-size:10.0pt;font-family:"Courier New";color:red'>Thank you.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=red face="Courier New"><span
style='font-size:10.0pt;font-family:"Courier New";color:red'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 color=red face="Courier New"><span
style='font-size:10.0pt;font-family:"Courier New";color:red'>-M</span></font><font
size=2 face=Arial><span style='font-size:10.0pt;font-family:Arial'><o:p></o:p></span></font></p>
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