printing...static context?

[Shaggy Rogers]

I'm using this code to try to print an Array, and using this code

void display(){
Iterator listIterator = D.iterator();
while(listIterator.hasNext())
{
Disk printDisk =(Disk) listIterator.next();
System.out.println(Disk.toString());
}

}

however, I get the classic method toString cannot be referenced from a static context error. Not sure what I can do about this. Thanks

[Shaggy Rogers]

*print an ArrayList actually.

[Carol Enderlin]

I'm guessing you meant this, calling toString on the object you got from the iterator:

System.out.println(printDisk.toString());

Instead of this, calling toString on the class Disk:

System.out.println(Disk.toString());
[ October 24, 2006: Message edited by: Carol Enderlin ]

[Shaggy Rogers]

Now I'm getting classCastException errors

[Shaggy Rogers]

Iterator<DequeInterface<Disk>> listIterator = D.iterator();
while(listIterator.hasNext())
{
DequeInterface printDisk = listIterator.next();
System.out.println(printDisk);
}

NOw I'm using this code and my output looks like:

++++++ The number stored is2 on 0 at left
LinkedDeque@1f6a7b9

that LinkedDeque@1f6a7b9 should be a number.
>_<

I don't know what the I'm doing wrong.

[Keith Lynn]

Originally posted by Shaggy Rogers:
Iterator<DequeInterface<Disk>> listIterator = D.iterator();
while(listIterator.hasNext())
{
DequeInterface printDisk = listIterator.next();
System.out.println(printDisk);
}

NOw I'm using this code and my output looks like:

++++++ The number stored is2 on 0 at left
LinkedDeque@1f6a7b9

that LinkedDeque@1f6a7b9 should be a number.
>_<

I don't know what the I'm doing wrong.

It looks like your printing your reference to a LinkedDeque object instead of printing out what is stored in that object.

[Shaggy Rogers]

Oh, I'm just not sure how to print what is stored there

[Keith Lynn]

What is a LinkedDeque?

I mean what type of object is it?

[Shaggy Rogers]

LinkedDeque is an interface,
and I want to print the contents of the arrayList
ArrayList<DequeInterface<Disk>> D;

[Keith Lynn]

What are the methods in the interface?

[Shaggy Rogers]

interface DequeInterface<E> {
// add to left end
void addLeft(E obj);
// add to right end
void addRight(E obj);
// return number of elements in deque
int getSize();
// return reference to left end; deque unchanged; throw exception if empty
E peekLeft();
// return reference to right end; deque unchanged; throw exception if empty
E peekRight();
// if deque size <=1 make empty, else remove one element from both ends
void trimEnds();
}

[Keith Lynn]

It looks like the peek methods are the ones you want.

[Shaggy Rogers]

Alright, I'll give those a try, thanks =D

[Ernest Friedman-Hill]

You poor fellow -- you seem to have been wrestling with this for days.

You have an ArrayList which contains DequeueInterface objects. If DequeueInterface is (as it appears to be) an interface specifying a double-ended queue, then those queues contains Disk objects. In other words, you have a List of Queues of Disks.

So if you iterate over the ArrayList, each entry is a queue. If you print the queue, then it's the toString() in the DequeueInterface implementation that will be called -- that seems to be a class named "LinkedDequeue" in your case. Based on what you're showing here, that class doesn't override toString() at all, so you just get the version from Object that returns "LinkedDequeue@98739873".

But it looks like you want to print the Disk objects in the queues. So you need to print each Disk in each Queue; in other words, you need TWO loops.

Pardon me, but I have to make something up here: let's hope that DequeueInterface implements Iterable and therefore has a method "iterator()" just like the ArrayList one, which iterates over all the items in the queue. If it doesn't then this code needs to be adjusted, of course.

Anyway, you want to do something like

for (DequeueInterface queue: D) {
    for (Disk disk: queue) {
        System.out.println(disk);
    }
}

This would print all the disks in all the queues. You might want to somehow add markers to divide the displays for the different queues; that's up to you.

I hope this helps.