Cast an unmodifiable set

Question

I have a java.lang.Object that I can't cast. When debugging I notice that the Object is an unmodifiable set so I tried to cast it to a set but that didn't work (ClassCastException). Instead I tried

Set<SimpleUserBean> listOfSelectedItems = new HashSet<SimpleUserBean>(object)

But of course that isn't possible either since there is no such constructor for HashSet.

How would I go about solving this?

Why cannot you cast it? What's the output when you use `System.out.print(object.getClass().getName())` and `System.out.println(object.getClass().getTypeName())`? You could also use `Class> interfaces = object.getClass().getInterfaces` and get the info of the object at runtime to see what super type you may cast it in order to ease your work. — Luiggi Mendoza, Jun 05 '15 at 16:21
Are you sure you are casting the object to Set and not some kind of concrete Set? — DJClayworth, Jun 05 '15 at 16:58

score 2 · Answer 1 · answered Jun 05 '15 at 16:28

If the Object is a java.util.Collections.UnmodifiableSet or anything else that implements Collection, then you should be able to do new HashSet<>((Collection) object). That makes it clear to the compiler that you're trying to use the HashSet(Collection<? extends E> c) constructor.

mehta · Answer 2 · 2015-06-05T16:37:34.380

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Set listOfSelectedItems = new HashSet(object)

This is not possible. How about this.

Set<SimpleUserBean> listOfSelectedItems =  new HashSet<SimpleUserBean>();
listOfSelectedItems.addAll((Collection)object);

edited Jun 05 '15 at 16:37

answered Jun 05 '15 at 16:31

mehta

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score 0 · Answer 3 · edited Jun 05 '16 at 16:42

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Convert java.util.Collections.UnmodifiableSet to String arrays.

Use :

object.getValue().toString().replace("[","").replace("]","").split(":")

Assuming object.getValue() will give you java.util.Collections.UnmodifiableSet

edited Jun 05 '16 at 16:42

Rahul Mane

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answered Jun 05 '16 at 15:53

user3785155

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Cast an unmodifiable set

3 Answers3