Drools - using accumulate to find min and max - drools

Question

I have a drools question which has been troubling me for some time. I want to find out the min and max price from a list of Item objects (contains price) using accumulate. A Member object (which contails list of Item objects) is inserted which contains the list of Items.
groovy/java source pseudo code
-------------------------------
class Item {
BigDecimal price
}
class Member {
List<Item>> items
}
...
droolsStatefulSession.insert(member)
session.fireAllRules()
...
rule.drl
---------
rule "rule1"
when
member : Member ($itemList : items)
/*
*/
then
System.out.println("condition met...")
end
Now the questions is in the above rule is it possible to if so how do I find out the item with the minimum Price and maximum price using drools accumulate feature. I do not want to use an java/groovy utility functions.
I see the "collect" feature allows to use "from" and then a datasource. I wonder if "accumulate" is similar to collect.

Answer 1

No need to use accumulate, just do something like
Item($lowestPrice : price, $id : id)
not Item(price > $lowestPrice, id < $id)
That's if your Items are inserted into the working memory.

Answer 2

I'm new to the drool rule and I'm trying to solve this issue.
You can find out min and max price of item simply - you have to write some rules and need to add two variable in the Order class:
Class Order
{
private List<Item> itemList;
private int highPrice;
private int lowPrice;
}
Using the following rule you can calculate min and max value of an item:
package com.sample
import com.sample.DroolsTest.Message;
rule "rule1"
when
$order : Order($itemList:itemList)
$item:Item() from $order.itemList
then
insertLogical($item);
end
rule "highPriceRule"
when
$order : Order()
$item:Item($price:price,price>=$order.getHighPrice())
then
$order.setHighPrice($item.getPrice());
end
rule "lowPriceRule"
when
$order : Order()
$item:Item($price:price,price<=$order.getLowPrice()||$order.getLowPrice()==0)
then
$order.setLowPrice($item.getPrice());
end
rule "highPrice"
salience -1
when
$order : Order()
then
System.out.println( "higher Item Price is "+$order.getHighPrice());
end
rule "LowPrice"
salience -1
when
$order : Order()
then
System.out.println( "Lower Item Price is "+$order.getLowPrice());
end
in main method you have to write this code and run it
List<Item> items=new ArrayList<Item>();
Item item1=new Item();
item1.setPrice(10);
Item item2=new Item();
item2.setPrice(20);
Item item3=new Item();
item3.setPrice(10);
Item item4=new Item();
item4.setPrice(5);
items.add(item1);
items.add(item2);
items.add(item3);
items.add(item4);
Order order=new Order();
order.setItemList(items);
ksession.insert(order);
ksession.fireAllRules();
output:---
Lower Item Price is 5
higher Item Price is 20
As I'm new to the drool rule I would like to ask if this is the correct procedure? Or is there another way to solve this problem?