Re: Interface Setter with List Generics

Thanks Joe Sam.

I do think I am more confused now. I thought I understood generics, but I'm
missing some things. Looks like it's time to find some good literature on
them.

Here is a snippet from "Using and Programming Generics in J2SE 5.0" (
http://java.sun.com/developer/technicalArticles/J2SE/generics/).

"It is worth noting that the draw() method can only be called on lists of
Shape and cannot be called on a list of Circle, Rectangle, and Triangle for
example. In order to have the method accept *any* kind of shape, it should
be written as follows:

public void draw(List<? extends Shape> shape) {
// rest of the code is the same
}

"

This made me assume that the setOrderLines(List<? extends OrdeLines>
orderLines) was the way to go. For now I have just removed the setOrderLines
from the interface until I can get this sorted out. There is something
that's just not connecting for me yet.

Thanks for the link though, it was a great article.

James R. Perkins


On Tue, Jan 13, 2009 at 21:41, Joe Sam Shirah <joe_sam@xxxxxxxxxxxxx> wrote:

Hi James,

Take a look at "Going wild with generics, Part 2", especially "The
get-put principle" at:


http://www.ibm.com/developerworks/library/j-jtp07018.html?ca=dgr-lnxw16javagenerics2&S_TACT=105AGX59&S_CMP=GR

HTH,


Joe Sam

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----- Original Message -----
From: "James Perkins" <jrperkinsjr@xxxxxxxxx>
To: "Java Programming on and around the iSeries / AS400"
<java400-l@xxxxxxxxxxxx>
Sent: Tuesday, January 13, 2009 7:17 PM
Subject: Interface Setter with List Generics

Hello All,
There may be some posts or other information out there but for whatever
reason I can't seem to find it. This is the closet I got, but did not

find

a
real answer.
http://forums.sun.com/thread.jspa?threadID=5142452

I have an interface for Orders and OrderLines. The Orders interface has a
method like so:
public void setOrderLines(List<? extends OrderLine> orderLines);

I was getting compile errors when attempting to compile the a
CustomerOrder
class that implements the Order interface. The setOrderLines() method I
expected to be able to override as such:

public void setOrderLines(List<CustomerOrderLine> customerOrderLines)

{

for (Iterator<CustomerOrderLine> iterator = customerOrderLines
.iterator(); iterator.hasNext();) {
CustomerOrderLine customerOrderLine = iterator.next();
this.customerOrderLines.put(customerOrderLine.getLineNumber(),
customerOrderLine);
}
}

But I ended up with this:
@SuppressWarnings("unchecked")
public void setOrderLines(List<? extends OrderLine>

customerOrderLines)

{
for (Iterator<CustomerOrderLine> iterator =
(Iterator<CustomerOrderLine>) customerOrderLines
.iterator(); iterator.hasNext();) {
CustomerOrderLine customerOrderLine = iterator.next();
this.customerOrderLines.put(customerOrderLine.getLineNumber(),
customerOrderLine);
}
}

Am I doing something wrong? The getter method that returns a List I was
able
to implement as expected.

Just thought one of you Java experts might have some insight for me.

Thanks in advance,
James R. Perkins

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