Originally posted by: Bahman

Hello Everyone,

I am learning to code optimization problems using Java API and I have an issue in saving the last constraints of the following simple LP into the Array List named Constraints. without that, the code runs, however, an error pops up as I make this line of code active:

Constraints.add(model.addEq(proportionalWeight[j], y));

instead of the following line:

model.addEq(proportionalWeight[j], y);

please find the code attached. 

I would really appreciate if you could help me out with this issue.

Regards,
Bahman 

The problem is this:

• proportionalWeight[j] is an instance of IloLinearNumExpr
• y is an instance of IloNumVar
• hence overload resolution picks this overload of addEq: IloConstraint addEq(IloNumExpr e1, IloNumExpr e2)

As you can see, this returns an instance of IloConstraint, not IloRange. Hence you cannot put the returned object into a list of IloRange instances.

There are a number of remedies, including:

• Change the type of the list to be a list of IloConstraint instances
• change the addEq() call to something that will use an overload that returns a range, for example addEq(model.diff(proportionalWeight[j], y), 0.0)

Originally posted by: Bahman

Hi Daniel,

Thank you! Both of the remedies actually worked. I appreciate it.

Regards,
Bahman Bornay