How to use a custom class as a type variable for an Iterator?

I have the following code using generics:

Set membersKeySet = membersList.keySet();
Iterator<DoubleKey> membersItr = membersKeySet.iterator();
while(membersItr.hasNext()){
    DoubleKey<Integer, Integer> dk =  membersItr.next();
}

Eclipse tells me that "Set is a raw type. References to generic type <E> should be parametrized". DoubleKey is also a Generic class. What I understand is that the .iterator() method doesn't assure that the DoubleKey Class has been passed with the same parameter types. I tried typecasting but it doesn't work. How can I pull this off? Thanks!

P.S. I'开发者_开发问答m still n00b inusing Generics.

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If the objects stored in the set are instances of DoubleKey<Integer, Integer>, then the code should look like this :

Set<DoubleKey<Integer, Integer>> membersKeySet = membersList.keySet();
Iterator<DoubleKey<Integer, Integer>> membersItr = membersKeySet.iterator();
while(membersItr.hasNext()){
    DoubleKey<Integer, Integer> dk =  membersItr.next();
}

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You should define type of the keyset.

Set<DoubleKey> membersKeySet = membersList.keySet();

Could you please provide memberList definition to provide the full picture?

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Well depending on what membersList is, I'd expect this to be the solution:

Set<DoubleKey> membersKeySet = membersList.keySet();

If membersList is also declared using a raw type, it becomes trickier... but we'll cross that bridge when you've checked whether that's all you need :)

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From the code you give, it looks like membersList is actually a map of some sort. So, in order to get the compile time type safety of generics, membersList should be defined appropriately, something like

Map<DoubleKey, Object> membersList = new HashMap<DoubleKey, Object>();
Set<DoubleKey> membersKeySet = membersList.keySet();

With that, your iterator should work as you have it.

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Normally you'd use the compact for-loop notation:

while(DoubleKey<Integer, Integer> dk: membersList.keySet()) {
}

And if you are using DoubleKey<Integer, Integer> all over the place, consider making it a class all on its own:

class IIKey extends DoubleKey<Integer, Integer> {}