maximum of list

[vijay yadav]

I have a field of type list

private java.util.list<java.lang.Double> income

How can I get max of this list using guided rule?

Collections.max(income) is not working.
can it be done using from accumulate?


Regards
Vijay

[José Filipe Neis]

Yes, it can. This link has some examples: http://blog.athico.com/2007/06/accumulate-functions-edson-tirelli.html

[vijay yadav]

None of these are working.
I have a class named "Test" which contains this list type object. Now I need to get the maximum of this list.
I think Accumulate iterates over all the objects and return max of all of these objects. but I have only one object with a field of type list and I need to get max of this.

[José Filipe Neis]

Do you need max on LHS or RHS of the rule?

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[vijay yadav]

Would you please tell me how can I do it in LHS?

On Wednesday, August 23, 2017 at 11:44:09 AM UTC+5:30, vijay yadav wrote:

[José Filipe Neis]

Vljay,

Writing the rules will follow the same kind of pattern you used in your example, but remember that now you have a List. What does this influence? That Drools will match your objects if they are equals (and list.equals(list) is not a trivial thing to match).

If I would give you any advice right now is: avoid using a List as a session object, but I really don't know your business requirements as you didn't talk about them at all so far.

Anyway, to write a rule that matches a property a list inside another object, you can use contains/memberof or a condition like the one exposed on this SO question:

rule "some rule name"
when
$a: A($bset : bset)
$b: B(x == "hello") from $bset 
then
//you will have one activation for each of the B objects matching //the second pattern end

In this example I understand that A would be your test class and bset/B your list type.

Filipe

[José Filipe Neis]

Sorry, I answered your question thinking about another question in the group. No contains/memberof applies to your case.

What you need to do is something like a showed, but use a accumulate function then:

rule "some rule name"
when
$a: A($bset : bset)

accumulate(

$b: B from $bset;

...

)

then